TASGC Scoping Study - Appendices

A report for Defra June 2008 Issue 1

TASGC Scoping Study - Appendices A report for Defra June 2008 Client reference: Report reference: D5175 - R1 Issue 1

This document has been prepared by Risk Solutions in connection with a contract to supply goods and/or services and is submitted only on the basis of strict confidentiality. The contents must not be disclosed to third parties other than in accordance with the terms of the contract. Risk Solutions is a trading name of Risksol Consulting Ltd. © Risksol Consulting Ltd 2008

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TASGC Scoping Study - Appendices Issue 1

Table of Contents

1 Introduction 1

2 Consultees and references 3

3 Work Package 1: Impacts 6 3.1 Climate change 6 3.2 Impacts and adaptation 17

4 Work Package 2: Emissions pathways 25 4.1 Emissions 26 4.2 Concentrations 28 4.3 Overshoot 30

5 Work Package 3: Policy options and technological measures 32 5.1 Global and Regional studies 33 5.2 Sectors 34 5.3 Geo-engineering options 39 5.4 Policy instruments 40

6 Work Package 4: Long term targets 44 6.1 Setting targets 45 6.2 Decision-support approaches 48 6.3 Facilitating agreement 54 6.4 Implications of targets 54

7 Work Package 5: Behavioural Aspects 56 7.1 Behaviour of individuals 56 7.2 Communication and dialogue with individuals 58 7.3 Behaviour of business 60 7.4 National government and local authorities 61 7.5 International perspectives 61 7.6 Wider perspectives 62 7.7 Research questions 62

8 Bibliography 66 8.1 Work Packages 1 and 2 66 8.2 Work Packages 3 and 4 67 8.3 Work Packages 5 68

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1 INTRODUCTION

Defra are considering the development of a comprehensive, multifaceted research framework on the technical aspects of the stabilisation of atmospheric concentration of greenhouse gases. The aim of the proposed research framework is to bring together and develop the evidence that is required to form policy related to agreeing and achieving a long-term stabilisation goal. This includes scientific and economic evidence related to the following work packages: 1. Impacts of climate change 2. Emissions pathways and concentrations of greenhouse gasses 3. Policy options and technological measures 4. Long term targets 5. Behavioural perspectives on climate change The work packages are broadly related as shown in the figure:

emissions pathways (WP2) How would GHG emissions have to change now and in the future to achieve different stabilisation levels?

policy options and Impacts (WP1) technological measures (WP3) How does stabilisation level How can target levels be achieved and at affect the climate and human what cost? welfare?

long term targets (WP4) At what level should targets be set to achieve the optimal balance between costs of mitigation and the risks of climate change?

behavioural perspectives (WP5) How will individual and institutional beliefs and valuations help or hinder efforts to achieve targets?

Risk Solutions supported by an expert panel was appointed to scope the proposed research framework. The expert panel is drawn from a number of institutions renowned for research in climate change including the Met Office Hadley Centre, the University of Cambridge, the University of Cardiff and the University of Leeds (see further details in Section 2 of these appendices). Scoping the research programmes required identifying where the critical research gaps are relevant to Defra’s need and developing these into possible research work packages. To understand where key uncertainties and gaps in the research lie we interviewed policy and research stakeholders, reviewed key secondary literature, ran a workshop of researchers to review and develop findings further and also held a separate meeting on economics issues.

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The key results and conclusions are presented in the main report. In the appendices (this report) we have summarised the information we have gathered under each work package. The appendices therefore provide a statement of our understanding of the gaps and uncertainties. Section 2 lists the main publications included in the review, the expert panel, and the policy makers and researchers interviewed. Sections 3 - 7 presents the results for each work package area. Section 8 presents a bibliography of useful references relating to each work package area. We have included in this report references to the source of information to provide an audit trail. P references refer to points raised in policy interviews and R references to points raised in Researcher interviews or by the experts on the project expert panel who reviewed the appendices. Points raised have not been attributed in this report to individual interviewees, the P and R numbers do not correspond to the order in the tables in Appendix 2. The references to documents do refer to the numbered references given in the table in Appendix 2.

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2 CONSULTEES AND REFERENCES

Name Organisation Policy consultees Molly Anderson Environment Agency Keith Brierley Environment Agency Adrian Butt Defra David Curran BERR Ben Day HMT Chris Dodwell Defra James Dyer Defra Paul Gilham Defra Nick Grout Government Office for Science, supporting the CSA Claire Hawley Defra Graham Floater Stern team Aditi Maheshwari DfID Jeremy Martin Defra Brian Morris BERR Steven Muirs Office of Climate Change Frances Raynor FCO Hannah Ryder Defra Chris Sear Defra Chris Taylor DfID David Warrilow Defra Bob Watson Defra Roger Worth Dept. of Transport Researcher consultees Prof Neil Adger University of East Anglia / Tyndall Nigel Arnell Walker Institute Dr Richard Betts Met Office Hadley Centre Dr Tom Downing Stockholm Environment Institute, Oxford Centre Dr Michel van Elzen MNP Netherlands Prof Michael Grubb Carbon Trust and Imperial College Debbie Hemming CEOSA Defra and Met Office Hadley Centre Prof Sir Brian Hoskins Grantham Institute and Chairman Met Office SAC Prof Tim Jickells University of East Anglia Diana Liverman Environmental Change Institute, Oxford Karsten Neuhoff Faculty of Economics, University of Cambridge Vicky Pope Met Office Hadley Centre Colin Prentice QUEST Dr David Reay University of Edinburgh Dr Gavin Schmidt NASA / Goddard Institute for Space Studies Dr Emma Tompkins University of Leeds Dr Rachel Warren Tyndall Centre Chris West UK Climate Impacts Programme Dr Detlef van Vuuren MNP Netherlands

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Workshop attendees (7 March 2008) Name Organisation Syndicate Olivier Boucher Met Office WP 3 & 4 David Frame University of Oxford WP 3 & 4 Joanna House Bristol University WP 3 & 4 Chris Huntingford CEH Wallingford WP 1 & 2 Tim Jickells University of East Anglia WP 1 & 2 James Kopka Defra CCE WP 3 & 4 Jason Lowe Met Office Hadley Centre WP 1 & 2 Kathy Maskell Walker Institute WP 5 Maria Noguer Walker Institute WP 1 & 2 Jean Palutikof IPCC WP 1 & 2 Nick Pidgeon Cardiff University WP 5 Alexa Spence Cardiff University WP 5 Debbie Hemming Defra CEOSA WP 5 Chris Sear Defra CEOSA WP 3 & 4 Jo Thorpe Defra CEOSA WP 1 & 2 Tony Quigley Independent for Risk Solutions All Ian Dunbar Risk Solutions WP 1 & 2 Richard Wheldon Risk Solutions WP 5 Helen Wilkinson Risk Solutions WP 3 & 4

WP3/4 Economists meeting attendees (18 March 2008) Name Organisation Hannah Ryder ICC/CCE, Defra James Kopka ICC/CCE, Defra Jim Penman CEOSA, Defra Stephen Prichard OCC, Defra Helen Wilkinson Risk Solutions

Project expert panel Name Organisation Prof Piers Forster University of Leeds Dr Jean Palutikof IPCC WG II / Met Office Dr Jason Lowe Met Office Hadley Centre Dr Terry Barker University of Cambridge Prof Nick Pidgeon Cardiff University Dr Alexa Spence Cardiff University Tony Quigley Independent

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The following references were used as the initial source of information on gaps and uncertainties in the research. Additional references are presented in the technical appendices that follow.

References 1. IPPC Assessment Report 4, Working Group 1 2. IPPC Assessment Report 4, Working Group 2 3. IPPC Assessment Report 4, Working Group 3 4. The Stern Report 5. Avoiding Dangerous Climate Change 6. A strategic assessment of scientific and behavioural perspectives on ‘dangerous’ climate change (Tyndall Centre Technical Report No. 28, June 2005) 7. Dangerous Climate Change: The Role for Risk Research (Introduction to special issue of Risk Analysis, 2005) 8. Oppenheimer et al, Science 14 September 2007: Vol. 317. no. 5844, pp. 1505 – 1506 9. National Security and the Threat of Climate Change, US Military Advisory Board 10. Reducing the Social and Economic Impacts of Climate Change and Natural Catastrophies: Insurance solutions and public-private partnerships. CEA Insurers of Europe 11. Climate Change: Everyone's business. A report from the CBI Climate Change task force

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3 WORK PACKAGE 1: IMPACTS

The research gaps and uncertainties relating to WP1 have been discussed under two main headings: • Climate change, and • Impacts and adaptation. The figure illustrates the main topics examined under the three areas and the relationship with other work packages.

WP1: IMPACTS

GHG and aerosol levels vs time (rate and stabilisation level) WP2

forcing mechanisms (role of cloud cover, water triggers/thresholds/feedbacks vapour, aerosols,…) (carbon cycle, natural methane,…)

climate changes (temperature, wind, precipitation, circulations,…) abrupt/irreversible changes extreme events (circulations, ice sheets,…) (weather patterns, flooding, storm surges,…) geophysical changes (sea level, ice cover, acidity,…) WP2 human and natural system impact by region (eco-systems, water and land availability, agriculture, health,…) scenarios

range of uncertainty socio-economic impacts by region (accounting for risks (demographic, political, economic,…) WP3 and uncertainties, impact of adaptation WP5 assumptions,… ) costs (& benefits) costs of autonomous/ of impacts planned, limits total damage cost of impacts WP4

3.1 Climate change

An argument is sometimes made that the big questions regarding climate change have now been answered and that work on understanding and modelling climate change is in the area of diminishing returns. However, while confidence in large-scale attribution and the prediction of global mean temperature has increased, the distributions expressing the uncertainties in key variables remain wide (and have long tails) and the impact of increasing GHG concentrations on many other variables at the regional level, including rainfall and storm intensity and frequency, are poorly understood. Although there is still climate science to be done, most of the easy problems have been solved. The remaining problems are there, not because they have gone unrecognised or have lacked investment. They remain because they are hard problems. The key remaining

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problems are: ice sheet behaviour, changes in regional temperature and precipitation patterns, extreme events and aerosol and cloud physics [R21]. If we knew with more certainty what climate and geophysical changes to expect, then it would be easier to determine the impact on human and natural systems, to gain acceptance for and to put in place proposed mitigation and adaptation measures. These results will give policy makers a more concrete picture of the type of outcomes that are likely to happen. This will in turn help them be clearer about what they mean by ‘dangerous’, or at least by the relative terms ‘more dangerous’ and ‘less dangerous’ [R18]. Key questions identified by Defra in this area include: 1. How do the risks of climate change depend on the stabilisation level and the rate of climate change? Including: c. Changes to natural modes of variability, such as El Nino, the monsoons and the North Atlantic oscillation b. Sea level rise, including the contributions from ice sheets d. Ocean acidification. 2. Are there any ‘trigger’ points (in terms of temperature or stabilisation level) above which the climate might change abruptly or irreversibly? Including: a. Positive feedback effects, or runaway climate change, from (for example) the carbon cycle or natural methane emissions b. Shifts in the form of important atmospheric or oceanic circulations, such the Atlantic Thermohaline Circulation c. Irreversible melting or collapse of the polar ice sheets.

Radiative Forcing

The combined forcing effect of different gases is often expressed in terms of an equivalent

concentration of CO2. This is useful as far as it goes, but does not cover the non-forcing

effects of CO2 – ocean acidification, fertilisation, carbon cycle feedbacks. Once this is

understood, CO2 equivalent is a useful presentational tool, although it is important here to state which gases and aerosols are included in the equivalence statement [R18]. Also,

equivalent CO2 concentrations should not be used as input into carbon cycle models, because

most constituents have much shorter lifetimes than CO2 [R18]. While there is a high degree of confidence regarding the contribution of greenhouse gases to historic radiative forcing of temperature, areas of uncertainty remain. The main one is the role of aerosols and especially their impact on clouds and cloud albedo. While it is likely that aerosols (especially sulphate aerosols) are exerting a substantial negative radiative forcing [1], there remain significant uncertainties with regard to the net direct and indirect aerosol cooling effects [5]. The processes leading to modification of cloud properties by aerosols are not well understood and while some models have reported improvements in the simulation of some cloud regimes, generally significant deficiencies remain [1]. The greater uncertainty in the negative forcing terms introduces a noticeable asymmetry in the radiative forcing distribution [1]. Even if there are no targets set for stabilisation of aerosol emissions, their effect on forcing will need to be taken into account when setting targets for the gases, especially those over the next three to five decades. Research in the area of aerosols and cloud microphysics is well funded. There are people developing the models and carrying out measurements. The models have included the microphysics only recently, and still have only simple schemes. Although the processes are basically understood, the problem is understanding what is important in the complexity. For example, the problem with rain is that there are a number of mechanisms for droplet growth. Therefore it is hard to predict which mechanism may be operating, and causing rain, in a

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particular potential rain cloud. The GCMs take from the microphysics a droplet growth rate, and use it to calculate rain on weather timescales [R21]. Many scenarios show fairly rapid reductions in man-made aerosol precursor emissions. Since the aerosol lifetime is quite short, these issues may be less important by 2100. However, they will remain important over coming decades. It is important to specify a range of aerosol scenarios alongside GHG mitigation scenarios. More work therefore needs to be done on the aerosol contribution to forcing. This is longer- term research, not something that can be completed on a 2-year timescale. Aerosol emissions and their forcing contributions need also to take into account non-anthropogenic aerosols: sea-salt, dust, biomass aerosols. A short term priority is to test the sensitivity of mitigation scenarios to the existing range of aerosol forcing estimates, even though these estimates may be changed by subsequent aerosol forcing research [R18]. Changes in land surface properties and land-atmosphere interactions that lead to climate change (either via radiative forcing or via feedbacks) are not well understood, especially on the large scale. It is also uncertain how land-use changes, some of which will be driven by climate change and climate change policies, will effect climate change through changes to surface reflectance, surface roughness and hydrology. These effects are considered likely to be substantial [5]. These changes are in addition to emissions of carbon and other GHG from land use changes. Spatial distribution of non-GHG forcing is important for regional changes. These are also uncertain. Some forcings are quite localised. These spatial variations are particularly important when considering land use and aerosols forcing. They would also be important if one were considering geo-engineering options.

Other areas of uncertainty related to forcing Other areas of uncertainty cited include: • The impact of contrails and their effects on cirrus cloudiness (and the impact of aviation generally, in the context of projections of aviation growth) – though these may be small [1] • The impact of stratospheric water vapour and what causes it to change, for example, the

oxidation of CH4 [1] • Spatial patterns of radiative forcing for ozone, aerosol direct effects, aerosol-cloud interactions and land use [1]. Uncertainties also remain in the assessment of natural forcings including natural GHG emissions (e.g. from volcanic activity [5]) and simulation and both past and future contributions of solar changes to radiative forcing [1]. This is a particular issue when considering regional affects because natural temperature variability is larger at the regional than at the global scale, which makes identification of changes due to external forcing more difficult [2].

Feedbacks

Confidence in attributing some climate change phenomena and understanding key climate change processes is limited by uncertainties in feedbacks [1]. The feedbacks can be divided into two types: those that affect the climate sensitivity and those that do not [R18]. Affecting climate sensitivity

• water vapour (excluding CH4 and irrigation sources), • lapse rate, • cloud changes (microphysics, cloud height, cloud fraction, lifetime), • surface albedo changes (e.g. snow, sea ice, (excluding human driven land use change and black carbon on snow – which are forcings).

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Not affecting climate sensitivity • carbon cycle, • methane, • long term ice-sheet changes (conventional climate sensitivity measurements take around 50 model years and do not include ice sheet changes or changes on longer timescales), • deep ocean circulation changes (for same reasons as above). A feature members of the first set have in common is a fairly fast response to forcing changes. Models differ considerably in their estimates of the strength of different feedbacks in the climate system [1] which could be substantial [R2]. Key uncertainties include: • Cloud and water vapour feedbacks: These are the most important. Between them they account for nearly all of the large range in climate sensitivity. As the water vapour feedback is positive and large – even a small uncertainty in this term has a large effect on climate sensitivity [R22]. • The carbon cycle: There is good evidence that, when the climate change is large and on a global scale, the feedbacks between climate change and the carbon cycle are positive (i.e. the impact of temperature and rainfall changes will be to reduce both the

terrestrial and oceanic carbon cycles’ ability to take up anthropogenic CO2) [1]. (Note that

in the case of the ocean, it is the fractional uptake of the additional CO2 that is reduced.

The total mass of CO2 that is taken up by the ocean increases with increasing atmospheric concentration.) For smaller changes, enhanced CO2 and more favourable climate may increase carbon uptake by plants. The magnitudes of the feedback between climate change and the carbon cycle are uncertain [1, 5]. They will depend on a number of factors including: ƒ The sensitivity of carbon absorbing systems, such as forests, oceans and soils, to future climate changes and to the rate of increase and level of carbon dioxide in the atmosphere. For example, higher levels of carbon dioxide can stimulate a higher rate of absorption by vegetation (the carbon fertilisation effect) [4, 5, R4]. ƒ Direct human influences, such as clearing forests for agriculture, for which the drivers for change are a complex mix of political, economic and climatic factors [5] (see below). These human influences are not feedbacks (except indirectly when the changes in human behaviour are caused by climate change) but they interact with carbon-cycle feedbacks. A particular difficulty in understanding and modelling the carbon cycle is the difficulty in scaling from experimental results to the ecosystem scale [8]. The fluxes of carbon from the tropics are very poorly constrained due to lack of data and methodological limitations [5] and are among the least understood and most uncertain major fluxes within the global carbon cycle [5]. The danger of substantial net carbon emissions from tropical forests in a globally changing world cannot be ignored [5]. However, a true runaway land carbon-climate feedback (or linear instability) in the future is considered unlikely given that the land masses are currently acting as a carbon sink [5]. There is more scope for using presently available information to reduce carbon cycle uncertainties. Current carbon cycle uncertainties range from 20ppm to 200pmm by 2100 (this 200ppm is on top of a 700pmm base case). However there are paleoclimate constraints that could be used to reduced these uncertainties. No interglacial went above 300pmm. Specifically the carbon cycle feedback effect is constrained by the experience in the Eemian to the 10s of ppm [R21].

• Other feedbacks of importance concern CH4 and N2O. Work on global models of

feedbacks associated with these gases started much later than for CO2 so much less is understood [R2].

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• The MOC response is likely to be the net result of a number of positive and negative feedbacks. Different feedbacks dominate in different models, and to obtain the correct net outcome it may be necessary to model each of the key feedbacks quite accurately [5].

Summary of Feedbacks Five main areas of feedback were identified: • cloud/ice albedo effects, • water vapour effects,

• CO2 fluxes,

• CH4 fluxes, and

• CH4 clathrate releases. There were differing views on current funding levels and future needs. One interviewee [R21] said that the first of these has ongoing funding, while the last three needed more support. Another [R22] said that all come under NERC’s remit equally, with lately more being funded on

CO2 feedbacks than anything else. All require sustained funding. There is a particular need to develop expertise in the last two (the methane issues). Work here has not happened, because of not having the people capability, rather than not having the funding opportunities.

An important CO2 flux issue is the net terrestrial CO2 fluxes to the atmosphere – whether they are negative or positive, and how the sign could change with temperature. It is important to note that this is not just a tropical rainforest issue. Boreal forests also make an important contribution to the fluxes. Work is needed here, but it is not something that can be done on a 2-year timescale.

Climate responses

Confidence in the assessment of human contributions to recent climate change have increased considerably since the TAR [1]. However uncertainties remain in how the climate has responded, and will respond in the future to changes in greenhouse gas and aerosol concentrations. An important uncertainty is that in the equilibrium climate sensitivity . This is defined as the change in the equilibrium global mean surface temperature, given a doubling of greenhouse gas concentrations from pre-industrial levels (approximately a concentration of 1 550 ppm CO2e) . Analysis of models and constraints from observations suggest that the climate sensitivity is likely to be in the range of 2 - 4.5oC and is very unlikely to be less that 1.5oC [1]. However it is not possible to place, through observations, a physical upper bound on this value. The climate sensitivity distributions share the characteristic of a long tail that stretches up to high temperatures. This is primarily because of uncertainty over clouds and the cooling effect of aerosols. For example, if cloud properties are sensitive to climate change, they could create an important addition feedback. Similarly, if the cooling effect of aerosols is large it will have offset a substantial part of past warming due to greenhouse gases, making high climate sensitivity compatible with the observed warming [4]. A number of uncertainty distributions of the climate sensitivity parameter have been proposed. The problem is that there is no objective way of choosing between them, especially when the differences lie in the subjective choice of Bayesian prior distributions. Other areas of climate response uncertainty include: • Forced changes in patterns of precipitation and surface pressure are more uncertain than changes in temperature [1]

1 Note, this should not be confused with the ‘climate sensitivity parameter’, λ, defined as the constant in the linear relation: (temperature change) = λ x (radiative forcing)

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• Behaviour of weather systems at the regional scale including blocking and phenomena in the tropics that organise convection [P11, R16] • Simulation of some major modes of circulations (ENSO, Madden-Julian Oscillation) and prediction of their responses in the future [1, 4] • Simulation of in situ ocean warming [1], and in particular, the differences between model predictions and observations of the variability • Precipitation at the regional scale [R8]; this is particularly uncertain but is important for impacts and adaptation studies. There are particular difficulties predicting precipitation in the tropics because of the complicated relationships between climate changes and natural circulations such as the El Niño [4]. From the perspective of impacts modelling, uncertainties in our ability to predict regional patterns of precipitation constitute the most important gap in our current knowledge. The workshop considered that what could usefully be done in the short term, without a great deal of effort, is to produce a map that colour codes the level of agreement or uncertainty over regional precipitation – analogous to the maps produced by Chris Milly on uncertainties about runoff, and the large scale diagram in AR4 WGI (Fig TS.30). It has however been questioned whether the current model predictions are reliable enough for this to be a meaningful exercise [R21]. Another useful short term activity would be to rank model projections for a region according to present day performance [R18]. • Biological feedbacks, that is, the loss of species and the degradation of ecosystems that have important impacts on the climate. • Extremes (see below). To relate GCM results to local behaviours the technique of statistical downscaling can be used. This involves looking for correlations between large-scale and small-scale behaviours, then using the large-scale predictions to get back to the local behaviours. There are situations however when the GCM simulations are too inaccurate for downscaling to work. This is particularly the case for the ENSO. The models have a persistent problem with tropical convection and rainfall in the Inter-Tropical Convergence Zone (ITCZ). The models cannot produce a coherent picture of the two zones. This could be related to the problems the models have with the Madden-Julian Oscillation (MJO). This means that we cannot predict the ENSO and other phenomena related to tropical precipitation into the climate-change future [R21]. The problem could be caused by mesoscale or even small scale effects, with the models being too coarse to capture the necessary physics. This said, much work has been done on this, and there is no obvious piece of missing physics. The models are highly coupled and stiff, and hard to shift from their predictions of these phenomena. This problem is unlikely to be solved simply by providing more money, more computing power or more model resolution. What is likely to be needed is a deeper understanding of the subtleties of the physics [R21]. Probabilistic calculations of regional precipitations on decadal timescales, and histograms have been produced. These calculations are however unvalidated. It is not correct to interpret the histograms as probability distributions. The more detail one asks for, the less robust the results become. For example there is likely to be less Mediterranean rain, but exactly where is uncertain [R21].

Geophysical changes

Sea ice extent and sea level rise There is high confidence that the rate of sea level rise accelerated between the mid-19th and the mid-20th centuries based upon tide gauge and geological data [1], and clear indications that anthropogenic greenhouse gases have contributed to this are now emerging [1]. However it has not been possible to establish with confidence from observations whether the ice sheets have been growing or shrinking over time scales of longer than a decade [1] –

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although proxy measurements (eg of last glacial maximum and interglacial) may tell us something about ice sheet behaviour too . As global temperatures rise, the likelihood of substantial contributions from melting ice sheets to sea level rise increases, but the scale and timing remain highly uncertain [4, R8]. A number of uncertainty distributions of sea level rise have been proposed. The main issue in the uncertainty is the behaviour of the ice-sheets (Greenland, West Antarctica). This drives the distribution tails. A current EU project bid, ice2sea, might help with this important uncertainty. Very different processes are at work in Greenland and the Antarctic, although they have important uncertainties in common, notably the understanding of fast ice stream processes. Greenland is mainly a land-based ice-sheet, and it looks at the moment as though the lubrication effects of melt-water at the base of the ice sheet may be critical to the rate of loss of ice. However, observations are only available for a relatively short period of time, and it is not clear if this process is really accelerating, or how widespread it is [R8]. Lubrication can be the cause of fast moving localised ice streams, and is also involved in the flow of ice sheets on larger scales (the Zwally effect). With the West Antarctic Ice Sheet the main effect is the loss of ice into the ocean, due to warmer water. Again how the global climate is actually affecting this and at what rate (and what other factors are important) are poorly understood [R8]. To improve this we need to simulate ice streams, ice shelves, interaction of streams and shelves, and local ocean changes under ice shelves. Some people now believe that the AR4 predictions of sea level rise could be underestimates. The models used to make these predictions have been unable to simulate the measured rises in the past and it is not yet clear why [R6, 8]. The headline sea-level rise table in AR4 omits the possible effects of dynamic ice sheet changes. This omission is explicitly acknowledged in the description of the table, so what is presented is strictly correct. However without the ice- sheet effects the information is incomplete. Sea level rise, as a function of time, remains therefore a huge uncertainty. This is mainly driven by ice sheet behaviour. The models are missing some known physics, and so their predictive value is limited. Also it will take time to assimilate the observations of ice sheet behaviour, so that the models can be informed by the results of the observation [R21]. Historically the development of ice sheet models was underfunded – it was effectively a cottage industry. It was then seen as an opportunity for investment, particularly in the US, and there are people working on the models. At the moment the GCMs have very simple ice sheet models. The ice sheets have decadal, centennial behaviours, that are not in the original models. There is therefore a need to couple them to the GCMs in an intelligent way. There is a big push to integrate icesheet models with the GCMs, while at the same time upgrading the models themselves. This will take years rather than months to complete, and will not be ready for AR5 [R21]. There are different types of ice sheet contribution. One of those is when surface melting exceeds precipitation over the ice sheet and water runs off the ice sheet into the ocean. This is included in the table 10.7 in AR4, WGI and is reasonable. However, there is now concern that dynamic changes (notably via fast ice streams) might lead to more rapid flow of ice into the ocean from the ice sheet. AR4 includes a crude estimate of this latter term (10 to 20cm) but acknowledges there is little basis for the 10 to 20cm estimate and that the correct answer might be considerably more (or less). The key unanswered questions are: how much more and how likely [R18]? There is a large uncertainty on sea-level rise predictions, especially those made for times beyond the 21st century [5]. However, a fairly robust result is that sea level response times to thermal expansion are large. This means that sea level changes are likely to continue long after GHG concentrations have been stabilised and thought should be given to how best include this in stabilisation discussions.

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Specific areas of uncertainty include: • Ice sheet basal conditions are generally poorly characterised [1]. • Models do not include full treatments of ice dynamics and may underestimate ice flow contributions to sea level rise [1]. The magnitude of the effect is unknown [1]. Improving this will require both a modelling effort and further observations. • Detailed regional variations in sea level rise resulting from non-uniform patterns of temperature and salinity changes in the ocean, changes in the time mean pattern of atmospheric surface pressure, and changes in the depth mean ocean circulation are highly uncertain, differing greatly between models [5], although some progress is being made on understanding why there is this variation. For scenarios with extensive ice melt it might also be necessary to re calculate vertical land movement estimates and include gravitational changes. Note however that the disagreement between models is less for the sea level rise around the UK [R18].

Ocean acidification The pH of the ocean is decreasing more rapidly now than at any time for the past several

million years. Oceans are a major sink for CO2, and their ability to absorb it may be impacted by increased acidification, but this, and the impact on marine ecosystems, is poorly understood [R8]. Equilibrium pH levels are highly predictable given atmospheric

concentrations of CO2, although the link between emissions and concentrations is still uncertain. Only the timescale is really under debate once the concentrations are fixed [5]. The rate of acidification depends on vertical mixing changes in the ocean – these are poorly understood and potentially very important for ocean acidification. If vertical mixing slows down, then surface acidity will rise much faster than if vertical mixing remains as it is today [R22].

Thresholds

A key question is whether there are any physical thresholds above which the climate might change abruptly or irreversibly. Very little work has been done on irreversibility [R1]. The work that has been done has been in simple models and has looked at the likelihood of irreversible impacts of the Greenland ice sheet and Amazonian rain forest [R1]. Potentially important thresholds include: • Methane hydrate deposits – potentially large but still very uncertain methane releases might occur from thawing permafrost or ocean methane hydrates [5] (see above). Methane from the permafrost is expected to be released slowly. However ocean shelf clathrates could give rise to sudden emissions. • MOC – Changes in the MOC have been linked to abrupt climate change, and they are thus an important factor in defining dangerous climate change [5].2 However, the supposed ‘switch-off’ of the MOC is not an issue. Notable problems have been identified with the models that predict a likely and rapid switch-off during the 21st century for business as usual scenarios. Work to date suggests that it is very likely that the MOC will reduce, but very unlikely that it will undergo a large abrupt transition during the course of the 21st century [1]. Longer-term changes in the MOC cannot be assessed with confidence [1]. For low and medium emission scenarios with atmospheric greenhouse gas concentrations stabilised beyond 2100, the MOC typically recovers from initial weakening within one to several centuries. A permanent reduction in the MOC cannot be excluded if the forcing is strong and long enough [1].

2 The Atlantic Ocean Meridional Overturning Circulation (MOC) – so called in AR4 – was often previously referred to as the Atlantic Ocean Thermohaline Circulation (THC), for example in chapter 6 of ADCC.

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• Ice sheets – There are large uncertainties over the temperature rises at which collapse or irreversible melting of ice sheets might begin to occur [4]. While significant contributions to sea level due to the instability of the West Antarctic Ice Shelf (WAIS) are considered unlikely during the 21st century, there are large uncertainties, and it becomes more likely if global warming continues [5]. The TAR said that irreversible melting of Greenland was likely to occur if local temperatures rise above 2.7°C above pre-industrial levels [5], but AR4 replaced this number with the range 1.9 to 4.6oC. Other thresholds relate to tipping points for natural eco-systems, e.g. the Amazonian rain forest. A particular concern is that certain places in the world may be particularly vulnerable to dangerous and irreversible climate change, as a combination of both long term changes, trigger events and structural or demographic characteristics of the region such as poor governance, high population densities in Asian megadeltas. This can lead to regional collapse (e.g. areas of the world that become uninhabitable) but the pathways to such events are currently poorly understood. This needs to be researched much more systematically [R7]. AR4 identified the Arctic, Africa, small islands and Asian megadeltas as hotspots. Overall it should be understood that tipping points occur on regional, local, ecosystem scales. There are no global scale tipping points, in which the whole system goes into a different climate state (e.g. a ‘Cretaceous world’, or even more extreme, Venus). However, there are positive feedbacks with gases, and more complex aerosol feedbacks. Most of the work on

feedbacks to date has been on CO2. There is some limited work in AR4 on the shorter-lived gases; work to improve this is already under way [R21]. The main tipping-point problem is with ecosystems. It is very difficult to model them; they are not dealt with by GCMs. And yet small changes in ecosystems can have devastating impacts. Changes in rainfall patterns have an important impact on ecosystems [R21].

Extremes

Extreme events are very varied. It is not valid to make general statements about them, as if they formed a single uniform category. In the UK, the events are: big winter storms (including precipitation), blocking highs3 and heat waves [R21]. Simulation of a number of extreme events (e.g. extratropical cyclones and especially extreme temperature) has improved and some models can now simulate successfully the observed frequency and distribution of tropical cyclones [1]. Since the TAR, the observational basis of analyses of extremes has increased substantially, so that some extremes have now been examined over most land areas (e.g. daily temperature and rainfall extremes) [1], although the time series are still very short at some locations and continued monitoring should be encouraged. Moreover limitations in observational data and models still cause significant problems in a number of areas including (in increasing order of uncertainty): • Temperature extremes (hot spells and cold spells) • Tropical cyclone intensity [1] • Regional Precipitation – models generally simulate too little precipitation in the most extreme events [1] and model projections for extremes of precipitation show larger ranges in amplitude and geographical locations than for temperature [1] • Storm track, frequency and intensity [4]. Incomplete global data sets for extremes analysis and model uncertainties still restrict the regions and types of detection studies of extremes that can be performed [1]. A risk assessment for extreme events could usefully be carried out on a 2-year timescale, using the Fractional Attribution method. This method is commonly used to

3 These are high pressure areas that remain stationary, for example over the British Isles, for timescales of the order of weeks.

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explore the likely causation of events that have already happened. Here the suggestion is to enhance the assessment of risks of future extreme events, by saying, ‘the risk of X has increased and the cause is Y’.

Modelling, methods and data

AOGCM modelling Because it is not possible to carry out experiments on the real climate (except on small scales, such as cloud modification experiments), climate models must be used instead, but there remain important uncertainties in how such models are constructed reflecting our incomplete understanding of the climate system [4]. Significant progress has been made in modelling in recent years. More models have been used in the simulation and projection of extremes, and multiple integrations of models with different starting conditions (ensembles) now provide more robust information about probability distributions and in particular their tails [1]. However climate models remain limited by the spatial resolution that can be achieved with present computer resources, by the need for more extensive ensemble runs and by the need to include some additional processes [1]. For example: • The resolution and inadequacies of typical models at the required spatial scales limit prediction of future changes, particularly at the regional scale and particularly with respect to tropical cyclones, precipitation changes and changes in extreme events [1, 2]. However the output from AOGCMs can be used to drive limited-area (or regional climate) models (RCMs) that combine the comprehensiveness of process representations comparable to AOGCMs with much higher spatial resolution. On a 2-year timescale it could be useful to examine how much value there is in downscaling (i.e. are we really downscaling climate change signal or variability) [R18]. • Differences in the spatial and temporal representation of present-day conditions may result in the response of some major modes of climate variability such as ENSO differing from model to model, and between models and reality [1]. • Models do not currently include full treatment of ice dynamics [1] and different types of ice sheet model tend to emphasise different mechanisms or controlling parameters [4]. • There is a need to look at not just how models treat clouds, but also at how they couple the clouds to the atmosphere in which they are embedded [R16]. Models deal with clouds in many different ways. Some are very crude (e.g. form layer cloud when relative humidity in a grid box goes above some critical fraction) whereas some try to explicitly model cloud processes (e.g. they parameterise droplet formation and growth). Both use some of the context of the atmosphere in which they are embedded but to different degrees. The biggest step forward would be trying to validate and tune individual processes in the later type of cloud scheme [R18]. • Models differ considerably in their estimates of the strength of some important feedbacks in the climate system [1] (see below). – some are well known like water vapour The inherently chaotic nature of the climate system, such that very small changes at one point in time can lead to completely different states at some future time, also limits aspects of attribution and prediction studies [4]. For example, apparent discrepancies between estimates of ocean heat content variability from models and observations may arise from uncertainties in model-simulated internal climate variability (as opposed to external forced changes) [1], although there could also be problems with the observations. Feedbacks: While many fast feedbacks are included in GCMs, the inclusion of other earth system feedbacks (carbon cycle, methane hydrates etc) is less common and more long term work should be encouraged. Ranges of projected warming and atmospheric composition in AR4 include an amplifying effect from interactions between climate and the carbon cycle. However, the estimated uncertainty in this effect is based largely on models that omit a

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number of poorly understood processes, such as feedbacks on carbon contained in permafrost; changes in marine ecosystem structure; and responses to land-use history, nutrient limitation, and air-pollution effects [8] (see above). The carbon cycle models used also shared similar assumptions about the temperature sensitivity of carbon fluxes from soils based on experimental results that cannot be reliably scaled to the ecosystem level [8]. Work on feedbacks is currently on-going, but different models still give a wide range of results. A need to test and benchmark the different models against observations and experimental results has been identified [R1, R2]. Metrics: Some metrics are devised to provide simple measures of a group of processes or

forcing (e.g. equivalent CO2 concentration). Others are observable quantities predicted by the models to be strongly correlated with future variables of interest (such as the equilibrium climate sensitivity). These metrics can be used to place constraints on model predictions (if a set of metrics is used for this purpose they must be statistically independent [R18]). Although complex metrics have also been developed based on multiple observables in present day climate, and have been shown to have the potential to narrow the uncertainty in climate sensitivity across a given model ensemble, a proven set of model metrics comparing simulations with observations that might be used to narrow the range of plausible climate projections has yet to be developed [1]. Scenarios: A need for more up-to-date standard mitigation scenarios to help compare model performance has been identified. IPCC are currently considering this issue (this is discussed further below). Interpretation of model outputs: When interpreting the findings of models two factors must be borne in mind: 1. Climate models are calibrated against a wide range of variables, against a general background of upward changes in emissions and concentrations. It is not clear how well they will perform under reducing emissions regimes and overshoot scenarios [R1]. This issue is particularly important for simpler climate models, which are usually tuned to the complex models using increasing forcing runs [R18]. 2. The climate modelling community worldwide is not large and modellers share methodological approaches. Consequently the models cannot be considered fully independent [4]. Narrowing in uncertainty based on agreement across models may be misleading where structural uncertainty remains in all models (for example predictions of changes in the MOC) [8]. IPCC AR4 use sophisticated techniques, including subjective expert judgement, to account for this in their estimates of likely ranges. These likely ranges are much larger than the inter-model ranges.

Data and observations High-quality observations are essential for understanding causes and for unequivocal attribution of present-day trends to climate change [2]. An important aspect of the IPCC’s work is to establish and communicate a consensus on what is actually happening and this relies on high quality sustained observational data [P12]. There are two distinct (but not mutually exclusive) reasons why further observation work may be recommended: • to improve the attribution of observed events, • to improve confidence in the projection of future climate. For any recommendation for further observations, the first step should be to determine which of these two is the primary objective. Areas where lack of observations or data limits understanding or models include: • past solar changes • ice sheet extent and basal conditions

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• other thresholds and feedbacks, for example the fluxes of carbon in the tropics are very poorly constrained due to a lack of data and methodological limitations • the regions and types of detection and attribution studies of extremes that can be performed • cloud observations – cloud behaviour makes a major contribution to spread in the climate sensitivity • the earth’s radiation budget, both at surface and at the top of atmosphere – now that the Earth Radiation Budget Experiment (ERBE) observations have been stopped [R22]. Timely monitoring of the pace of approaching significant thresholds is also required [2]. One of the data concerns is that climate observations are often made using weather observing systems, but these have different requirements. A major issue here is that climate data systems must plan for long term tracking of parameters e.g. a replacement satellite must be run in parallel with the outgoing satellite in order to cross-calibrate it. A second concern is the barriers moving from research observations to operational status as this will generally mean a change in funding and agency [R16]. Models may be able to help design the optimum observing networks by showing where and type of observations most useful for constraining projections or seeing first signs of a threshold change. Carrying out this design could be a 2- year action, so that putting in place a suitable observation network could be part of a negotiated agreement.

Analysis of existing results Rather than spend more money on the already funded areas of physics identified above, where work is ongoing, a better target would be the existing model results, for example, the AR4 archive of model simulations. There is a great deal of useful information still in there to be extracted. The basic information has been used: e.g. predictions of temperature and rainfall up to 2100, but there is a huge potential for more intelligent prediction, based on model-data comparison for 20th century, looking for variables where these comparisons could constrain the predictions of future trends. An example is seasonal rainfall in UK. One could look at all model predictions for last 30 years. There is a large spread in predictions, and comparing them actual values could produce useful constraints on model parameters [R21]. This work would best be done by specialists in computer science, artificial intelligence, and data mining, in collaboration with climate scientists. It would thus draw on a wider pool of expertise, and not just those who develop and run the climate models [R21].

3.2 Impacts and adaptation

Less work has been carried out to understand the impacts of climate change on human and natural systems (and the subsequent socio-economic impacts) and the costs, benefits and limits to adaption, than on the relationship between climate change and emissions of GHGs and aerosol precursors. As unacceptable, or dangerous, climate change must generally be defined in terms of these impacts. Understanding the needs for adaptation and mitigation relies on understanding (probabilistically) what different emissions pathways and mitigation scenarios mean in terms of impacts. This is therefore a critical component of establishing and agreeing targets. We need to understand, and articulate in meaningful terms, the impact of different levels of climate change on human activities. A 1m rise in sea level means very little to people. There is a need to present this in terms of what it means for impacts on human and natural systems and socio-economic systems both in the UK and abroad, for example: • on eco-systems, human health, water availability, flooding, and

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• food supply, security, migration, energy supplies. Key questions identified by Defra in this area include: 1. How do the risks of impacts of climate change depend on the stabilisation level and the rate of climate change? Including: a. Regional impacts, including extreme events, on natural and human systems (e.g. food production, water stress, health and ecosystems etc) e. The interactions between different types of impacts (i.e. integrated approach) – e.g. the effects of changes in ecosystems and extreme events on agriculture f. Understanding dependency of impacts on population and GDP.

Modelling impacts on human and natural systems

What is most needed is to be able to model the impact of climate change on humans, directly and via the ecosystems and the services they provide. In broad terms, the climate science is done and has been put in place. However the long term impacts depend on the global mean sensitivity, which is still uncertain. This requires longer term research, which has already started [R21]. It is difficult to capture all the interactions in impact modelling – there are many pressures on ecosystems and human systems other than climate change. Both types of system are most vulnerable to climate change when they are already stressed by other factors, for example, when human societies are already stressed by war or poor governance. Work on impacts to date has been largely: 1. concerned with case studies of very localised impacts or with a single type of impact [R2], or 2. very high level (e.g. concerned with establishing the total damage cost associated with different mean global temperature rises), these are generally based on very simple climate models, often effectively climate sensitivity tables, and use average values not distributions [R13]. There is a need for impacts to be studied in an integrated manner. This would look at impacts occurring together and feeding back onto one another and onto the climate system. In addition, the way in which impacts modify the potential for mitigation should also be taken into account [R18]. Sometimes complex climate models are used in conjunction with impacts assessment, but the data for building damage functions comes from simpler models, or from limited observations. Summarising the impacts based on existing GCM simulations would be a useful action on a 2- year timescale. To date there has been little effort directed towards fully integrating anything but the simplest climate models with impact models [R1] or looking at how multiple impacts affect such things as the vulnerability of a region and the spill-over impacts. Regional studies are also limited by the availability of climate models with appropriate spatial resolution and the range of uncertainties in predictions. A recognised shortcoming of AR4 is that it was weak on stabilisation (mitigation) pathways. There is a need to know more about the damages avoided by mitigation efforts (see under scenarios below) [R6]. There is a particular need to look at impacts for a high emissions scenario (because this has a high signal to noise ratio, and helps with our understanding of avoided impacts) and low end scenario (e.g. 450ppm stabilisation). We also need to look at impacts associated with climate surprises, e.g. MOC collapse. Improvements in modelling impacts may also require better communication between IPCC working groups. Policy guidance is required on the types and scales of impact that should be considered.

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Impacts on Ecosystems

Predicting the impact of climate change on ecosystems is very difficult [P12]. A particular area of uncertainty identified is the impact on marine organisms and ecosystems: There is very little research on the potential impact of ocean acidification on marine organisms and ecosystems or on the impact this might have when combined with other climate-induced changes [5]. The pH of the ocean is increasing more rapidly now than at any time for the past several million years and even at a 1°C temperature rise oceans will continue to acidify [5]. Organisms with calcium carbonate exoskeletons (shells), which can be dissolved in an acid environment, may not be able to adapt to this and may consequently become extinct. The vulnerable organisms are low down in the food chain. Their extinction may have major knock- on effects on the whole ocean ecology, including the fisheries that humans depend on for food [R8]. Another important effect for oceanic ecosystems is changes in stratification due to warming – for example, the reduction in nutrient rich upwellings of cold water. Important fisheries are dependent on the highly productive ecosystems associated with these upwellings. Other ecosystems at particular risk are: • corals: acidification, bleaching (temperature effect), • ice margin ecosystems, • mountain ‘island’ communities.

Impacts on Human Systems

Human impact issues include: • coastal flooding, • trade patterns, food and fuel supply and prices, • refugees, • disease spread (migration, insect vectors), • transport, • water runoff, • fisheries – e.g. cod moving north. These issues could usefully be structured by cause and effect. For example food shortages could be a primary impact, with the refugee problem being an effect of the shortages. The priorities here are the related issues of health and food supplies. Water management modelling needs improving, particularly with improved sea level rise estimates. A more general objective here is to develop integrated climate and impact models, with the appropriate feedbacks from human impacts to climate change, together with improved damage functions, as well as improving the climate components of such models. It may be possible here to use the method of pattern scaling, although this has yet to be tested rigorously for all pathways. The Community Integrated Assessment System (CIAS) could be used as a framework for such developments. This is not the only model capable of this; IMAGE might also be suitable, in which case including it would help avoid bias [R18]. More detailed considerations in specific areas include the following.

Water The impact of precipitation changes and changes in extreme events on future water resource availability is poorly understood. This is due in part to the inadequacies of existing climate models at the required spatial scales [2]. It also depends however to a very large extent on the future state of the world, and particularly on the numbers of people potentially exposed to water shortage [5] as well as on the effect of human water management scenarios.

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The key issues for modelling climate change impacts on water management can be summarised as: • dangerous sea level rise, • positive and negative changes in hydrology, • heat waves. Water management is also a field of activity where there is great scope for perverse incentives, which have to be considered when assessing policy instruments (see WP4 below) [R21].

Agriculture Agriculture will be affected by water and land availability and by the carbon fertilisation affect. Work on all these areas is on-going. In higher latitudes, such as Canada, Russia and Northern Europe, rising temperatures may initially increase production of some crops if the carbon fertilisation effect is strong (still a key area of uncertainty) [4]. The choice of crop model has been shown to provide a significant source of uncertainty in the simulation of yield under climate change [5]. Impacts on agriculture however depend on many factors in addition to climate, including for example prices and changes in land use. Impacts therefore need to be considered in the context of other climate and market factors [R14], and changes in agricultural technology, including the possible introduction of GM crops.

Health and malnutrition There is some work looking at affects on health in the UK, but work looking at impacts in developing countries may be a gap [P18] for example the impacts of climate change on child mortality and malnutrition in Africa this appears to be a significant gap [R6]. There is some work (e.g. at KCL) into heat related mortality. There is a need for more work on vector carried diseases. Work on climate change health effects needs to be linked to more general health forecasting.

Extremes and thresholds These were identified as key research gaps in the research paper 'Assessing impacts, adaptation and vulnerability: Reflections on the Working Group II Report of the Intergovernmental Panel on Climate Change'. There is very little research on impacts and vulnerabilities to sudden and larger changes such as Amazon drying or global temperature increases above 4 degrees for example. The uncertainties predicting the scale and timing of extreme, abrupt, or irreversible climate change events at a regional scale, limits the extent to which it is possible to account for them in impacts studies. This is an important omission for a number reasons: • It has been suggested that the way individuals and societies respond to climate change, mitigation and adaptation signals is closely linked to their experience, or understanding of the risks, of extreme events. • Certain places in the world (so-called 'hotspots') may be particularly vulnerable to dangerous and irreversible climate change, as a combination of both long term changes and trigger events that result in permanent damage and no bounce-back. This can lead to regional collapse (e.g. areas of the world that become uninhabitable) but the pathways to such events are currently poorly understood. • Without a better understanding of the risks of reaching and exceeding thresholds and of irreversible change it is not possible to devise appropriate ways of avoiding unacceptable risks. • Understanding extremes is important for adaptation decision making.

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High-end impacts An area where both researchers and policy makers [R1, P6, R13] have identified a need for additional information is the impact of high-end climate change (e.g. 4 or 5oC increases in mean global temperature by the end of the century, with regional mean temperatures possibly going higher than this). Such studies will help paint a clearer picture of the potential impacts in the absence of, or weak, mitigation and studies exploring the limits of adaptation. A critical question here is: is there enough information to say what the impacts of a 3 or 4oC rise will be, are there too few analogues in the world [R1]? High-end impacts need to be understood particularly in the socio-economic context (see next).

Socio-economic changes

Changes in the variability of climate in the future could have very significant impacts on lives and livelihoods. For example, India’s economy and social infrastructure are finely tuned to the monsoon, with the result that fluctuations in the strength of the monsoon both year-to-year and within a single season can lead to significant flooding or drought, with significant repercussions for the economy [4]. It is important to understand what characteristics enhance vulnerability, strengthen the adaptive capacity of some people and places, or predispose physical, biological and human systems to irreversible changes as a result of exposure to climate and other stresses [2]. Areas where specific gaps or uncertainties have been identified include: • The impact of abrupt and large-scale changes on the stability of regions and regional conflict [4] and high-end impacts (see above) on e.g. food supply, security, migration, water, energy supplies [P6]. At very high temperatures, the physical geography would change so strongly that the human and economic geography would be recast too. The full consequences of such effects are still uncertain, but they are likely to involve large movements of populations that would affect all countries of the world [4]. • Socially contingent impacts and the impacts of climate change in the context of other stresses, e.g. likelihood of conflict; mass migration; dislocations, reverberation of climate change impacts through the wider economy [P2, P9, P11, P18]. Climate change is likely to increase migratory pressures on developed countries significantly, although the potential scale and effect are still very uncertain and require considerably more research [4, P18]. • The implications for the UK of e.g. increased migration and immigration, food security [P9]. • Spill-over effects from mitigation (the effects of domestic or sectoral mitigation measures on other countries or sectors) [3]. • Trade interactions and innovations. Improved understanding of impacts and vulnerabilities will require a much more sophisticated analysis of changing global trade patterns and interactions, including food systems, biofuels, embodied water and carbon, and shifts in comparative advantage as climate changes. This was identified as a key research gap in 'Assessing impacts, adaptation and vulnerability: Reflections on the Working Group II Report of the Intergovernmental Panel on Climate Change' [R14]. • An important feedback to model is the effect of impacts on future mitigation potential. For example, mitigation measures which are currently feasible may become less so following climate impact induced economic downturn or societal stresses.

Adaptation

When establishing stabilisation targets it is important to understand the costs, benefits and limits to adaptation. Because of the inertia in the climate system, there will be a need to adapt to change that is already happening and cannot be practically prevented. It is generally

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assumed (although not universally accepted) that the impacts of climate change in the absence of mitigation will be so great that adaptation will be insufficient to prevent extremely undesirable consequences [5]. However it is also generally accepted that globally we are under-adapted even to present day variability [P12] and that more attention needs to be given to adaptation. The different policy approaches to adaptation that can be adopted have different economic and equity implications [R10]. AR4 found that the literature on adaptation costs and benefits is limited and fragmented. It focuses on sea-level rise and agriculture, with more limited assessments for energy demand, water resources and transport. There is an emphasis on the USA and other OECD countries, with only a few studies for developing countries [2]. There are few studies that examine what might be achieved by adaptation or that estimate the limits to or costs of adaptation [5]. Stern also found a mixed picture with some studies assuming no adaptation, many impact studies assuming individual (or ‘autonomous’) adaptation, while other studies assume an ‘efficient’ adaptation response where the costs of adaptation plus the costs of residual damages are minimised over time [4]. In assessing likely adaptations it has to be remembered that communities and individuals adapt all the time and may adapt, without government intervention or interference [R22]. 'Assessing impacts, adaptation and vulnerability: Reflections on the Working Group II Report of the Intergovernmental Panel on Climate Change' identifies observed impacts and adaptation as another area where research is required and identifies sectors such as industry and regions of the world such as most of the tropics as understudied. There appears to have been a lack of coherent progress on adaptation since AR4 [R6]. Adaptation options are highly localised and solutions more deeply context-specific [5]. Therefore one of the key challenges for adaptation studies is the uncertainty in regional climate predictions, particularly changing regional rainfall patterns [4] and extremes.

Total damage cost of impacts

AR4 (WGII) found only a small amount of literature on the costs of climate change impacts for assessment [2]. WGII concluded that regional costs aggregated and discounted to the present, are very likely to impose costs and that these are very likely to increase over time [2]. Specific estimates are however uncertain and should therefore be interpreted vey carefully. WGIII concluded that due to large uncertainties and difficulties in quantifying non-market damage, it is still difficult to estimate the social cost of carbon with confidence [3]. Indeed the usefulness of this measure has been brought into question, not only by the Stern review, but be the critical response. The upper bound of the ranged of the social costs of carbon appear to be unlimited. The limited discussion of damage costs and the social cost of carbon in WGII, difficulties in linking to the economic analysis in WGIII, and the inadequacies in costing damages in the Stern Report suggest that research on both the costs and benefits of impacts and adaptation will be helpful to integrated assessments and policy makers [R14]. Questions to be addressed include: What are the impacts (costs) of climate change on developed and non developed countries? What are the effects on their major industries? What are the costs associated with extreme events and high-end impacts. This is discussed further under WP4.

Modelling, methods and data

Scenarios 'Assessing impacts, adaptation and vulnerability: Reflections on the Working Group II Report of the Intergovernmental Panel on Climate Change' identifies the need for broader and consistent scenarios. A more creative and consistent set of socio-economic, technical and

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political scenarios is required. These should encompass new insights into socio-technical transitions, human behaviour and economics, and options for international and national climate policy. These will support research across the full range of IPCC activities (climate projections, impacts, vulnerability and adaptation, mitigation, emission trajectories) [R14]. Most AR4 studies of future climate change are based on a small number of studies using SRES scenarios, especially the A2 and B2 families. This has allowed some limited, but incomplete, characterisation of the potential range of futures and their impacts. A1B and B1 were more commonly used in AR4 WGI. Their lack of use in WGII highlights the inter-group communication and timing issue. The proposed AR5 scenarios include mitigation. Also the EU Ensembles project has developed a low end mitigation scenario called E1 to use with several GCMs in an intercomparison. Scenarios are required: • To describe the future evolution of the world under different and wide-ranging assumptions about how societies, governance, technology, economies will develop in future • At the regional and local scales appropriate for impacts analysis • Which allow adaptation to be incorporated into climate change impact estimates • For abrupt climate change • For large sea level rises due to ice sheet melting • For beyond 2100 (especially for sea-level rise). Among other things these should describe what the world will actually look like: • If we achieve various proposed 2050 targets [P7] • In an unconstrained and also in a climate constrained world (e.g. given air quality, deforestation etc policy interventions). Difficulties described in developing scenarios include: • Understanding the demographic and economic changes that must be combined with emissions factors to get more accurate projections [R4]

• Consistent treatment of non-CO2 GHGs in the methodologies underlying scenarios for future GHG emissions [3] • The uncertainty in the drivers of future change and their interactions; for example, the drivers of land-use change, in particular deforestation, are a complex mix of political, economic and climatic factors [5] • Understanding likely technology adoption rates [R14]. Mitigation scenarios are discussed further under WP3.

Risk assessment Risks are still very poorly understood; IPCC reports are not risk assessments [P7]. A key question here is how you build in a risk assessment approach to the consideration of impacts. This involves working out what matters to people and then presenting the information in terms of the likelihood of this happening under different scenarios [P11]. Some work in this area has been published e.g. [5] and MOHC work presents outputs in the forms of probability distribution functions for exceeding specific temperature, and for each of a range of temperature rises and emissions scenarios (2oC, 3oC etc) as follows: • the probability of not exceeding the target temperature, • the probability of exceeding the target temperature, but then returning to it, • the probability of exceeding the target temperature, and then not returning to it in a usefully short time. Risk based data for adaptation for the UK will become available through UKCIP08.

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Related to this is the need to develop methodologies that can account for low probability, high consequence events in economic impact models. Most existing economic analyses of climate change treat central forecasts of damages as if they were certain and then do some sensitivity analysis on parameter values. They rarely incorporate uncertainty at all into the structure and when they do often truncate PDFs at arbitrary cutoffs. Recent work by Weitzman has developed a method to include PDFs more fully in the economic model [P19] however this still relies on a conversion of risk to a certainty equivalent (i.e. an expectation value) and therefore is not risk analysis. Risk analysis retains the information in the tails of the consequence probability distributions, combining the magnitudes of the consequences with the probabilities to give a measure of risks. These challenges will be discussed further under WP4.

Modelling There are two main issues here, the limited ability of climate models to provide probabilised output at the regional scale required to support impacts and adaptation studies (discussed above under climate change) and the lack of fully integrated climate and impacts models. The individual component models need improving (e.g. the impacts models), and integrating these components needs more work.

Data and observations Debate still surrounds the topic of how to measure impacts, and which metrics should be used to ensure comparability [2] – and indeed whether it is possible or desirable to aggregate impacts in this way [5].

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4 WORK PACKAGE 2: EMISSIONS PATHWAYS

A subject that is currently being given much consideration by policy makers is the concentration level at which it is most appropriate to aim to stabilise atmospheric concentrations of green houses gasses. This debate needs to be informed by an understanding of how greenhouse gas emissions have to change now and in the future for different target stabilisation levels. And this needs to be considered globally and at a country level. To design mitigation strategies, policy makers also need to understand the risks associated with different emissions paths to stabilisation, and for example, the risk of overshooting any given target level. It is also important to understand the optimum balance of emissions reductions between different GHGs, in terms of damage cost avoided and mitigation cost. The research gaps and uncertainties relating to WP2 have been discussed under the main headings: • Emissions • Concentrations • Overshoot The figure illustrates the main topics examined under the three areas and the relationship with other work packages.

WP2: EMISSIONS PATHWAYS AND CONCENTRATIONS WP1 WP1 scenarios anthropogenic emissions from other emissions over sources WP3 time (methane from clathates,…) feasible mitigation pathways GHG & aerosol emissions pathways by GHG (different pathways, timing of peak,…)

removal to equilibrium irreversible removal (processes, rates, fractions,… (processes, rates, fractions,,…) air/water, air/land interactions,…)

concentration profile with time

overshoot of target range of uncertainty (rates of return to target, (accounting for risks risks of irreversible and uncertainties, overshoot,…) impact of assumptions,… ) GHG and aerosol levels vs time (rate and stabilisation level)

WP1

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The key questions identified by Defra in this area include: 1. By how much will global GHG emissions need to be reduced, over the next century and beyond, to stabilise GHG concentrations at levels between 400 ppm

CO2e and 750ppm CO2e? In particular: a. The risks and uncertainties related to current levels of scientific understanding b. The implications of delaying the peak in global emissions c. The implications of different emissions paths up to the peak 2. What are the risks associated with overshooting a target GHG level? In particular: a. Rates of reductions in concentrations under different scenarios b. Implications for temperature rise and impacts and their relation to the size and duration of the overshoot c. The risk of overshooting (irreversibly) d. Implications for emissions pathways and achievability of these pathways over the long term e. Sensitivity of risks to modelling assumptions (e.g. aerosols) and uncertainties in the science

4.1 Emissions

Pathways

The understanding and modelling of emissions pathways are moderately well developed

[P11]. While there is a tendency for work to focus on CO2, in recent years work such as the Equal Quantile Walk (Meinshausen et al) is enabling emissions from multiple gases to be considered. However it seems that the distributions of emissions used to define the quantiles in this study appear to be a poor representation of low emissions scenarios [R18]. There have not been enough emissions (and therefore temperature) pathways modelled for adequate impact assessments to be carried out [R6]. One possibility is to devise a really high- end scenario; even if it were thought to be unlikely, it would provide a high-impact baseline against which avoided impacts could be assessed for lower pathways, including mitigated pathways. Another issue is thinking more carefully about just what Business As Usual (BAU) entails – for example, to what extent should Kyoto compliance be included as part of BAU. Further work may also be required to create realistic mitigation pathways for more complex models [P11]. There are also specific emission pathways which may benefit from further analysis. For example, as tropical wetlands warm, then this may result in additional emissions. However, currently this is uncertain [4]. Pathways could also be enhanced by including land-use scenarios in their definition. Emissions have been growing faster than expected in recent years, it is important to understand this and to take it into account in predictions of future emissions: • What are the variables? • Are the causes 'structural' or due to high economic growth in some parts of the world, such as Asia, • Will these trends continue? • How has the high oil price affected emissions and will the price stay high? [R15] Another way of thinking about the pathways question is in terms of responses to credible emissions corridors. An emissions corridor is wider than a single path, and is such that any

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path through the corridor would lead to the same stabilisation outcome. The specification of an emissions pathway, or corridor, should include aerosol emissions, as they have a big impact on early peaking scenarios. On the other hand, impacts modellers do not want many more pathways, and the corresponding large amount of additional climate change output to analyse. Judicious use and modification of the existing pathways may meet the needs described above. Pathway development is not a new piece of work. Consideration of the development of new pathways, or modifying the existing ones is already under way, under the auspices of the IPCC.

Other gases and aerosols

Understanding of gases other than CO2 needs selectively improving, for example:

• The error margin on current CH4 and N2O emissions is high; it is estimated to be in the order of 30-50% [3]. • There is considerable uncertainty whether methane hydrate deposits will be affected by climate change at all [4].

• SO2 emissions are at present reducing the warming effect, depending on location, but as

SO2 emissions are reduced directly e.g. through flue gas desulphurisation, or indirectly though reductions in combustion of fossil fuels, then the cooling effect will be reduced

and the carbon cycle may be further weakened. Again the influence of SO2 and soot and other particles on temperatures and the carbon cycle feedbacks are subject to high error bounds. • There is also considerable uncertainty in the estimates of anthropogenic aerosol emissions. In particular, data on non-sulphur aerosols are sparse and highly speculative [3].

It is important to include aerosols and gases other than CO2 explicitly in the description of

emissions pathways (and not just as a CO2 equivalent), because of the different timescales on

which they act. CO2 is the long term problem, that will not go away quickly, and is closely tied to economic activity. However the other greenhouse agents: methane, tropospheric ozone,

black carbon, organic carbon, collectively have as big an impact as CO2. Because of their shorter lifetimes, they are easier to control. For example if we were to stop anthropogenic methane emissions, concentrations would be back to preindustrial levels in a few decades. For black carbon emissions this timescale would be around 3 weeks. The CCSP report about to come out will contain a more comprehensive assessment of differing emissions [R21].

Sectoral knowledge

Since 1750, it is estimated that about 2/3rds of anthropogenic CO2 emissions have come from fossil fuel burning and about 1/3rd from land use change [4]. Estimates for average 1990s emissions indicate that these fractions have now shifted to 4/5ths from fossil fuel burning and

1/5th from land use change. It is also estimated that currently about 40% of total N2O emissions are anthropogenic. However there are still gaps in accurate and reliable emission

data by sector and specific processes. This is particularly the case for non-CO2 GHGs,

organic or black carbon, and CO2 from various sources, such as deforestation and associated land use change, decay of biomass and peat fires [1, 3 & 4].

Energy There is uncertainty here related both to the demand for energy and to how the emissions resulting from power generation will change: • Energy demand and hence emissions are likely to change as a result of climate change, but the direction of the net impact is uncertain. Warmer winters in higher latitudes are

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likely to reduce energy demand for heating, but the hotter summers likely in most regions are expected to increase the demand for refrigeration and air conditioning [4].

• Fossil fuel burning is associated with SO2 release and other particulate pollution, which may exert a negative radiative forcing, although this is expected to reduce in future as a result of clean-air technology [5]. • Critical issues for future GHG emissions include how quickly new coal plants are going to be equipped with CCS technology [3] and the effectiveness of mitigation measures such as the carbon markets. • In the domestic sector there is a good understanding of emissions and expected trends in energy use and effects of different technologies [R4].

Transport Data on current transport usage and trends in volume and associated emissions is generally well developed. However there are specific areas of uncertainty including: • It is difficult to measure NOx emissions at altitude and so there is limited information available on what the emissions throughout a whole flight are [P8] – although cirrus clouds and contrails are likely to be more important than NOx. There are few organisations looking in to NOx emissions and contrails. MMU (Prof David Lee and colleagues) is leading the OMEGA programme on aircraft effects, which includes, Leeds, Cambridge and Reading. • Shipping is believed to have similar levels of effect to aviation but this is uncertain [P8]. Some work on this is being done at Reading (EU quantify project).

Waste and agriculture Waste and agriculture are diffuse and small sources. They have potential for a very large

contribution in total. There are pockets of specific knowledge, for example the UK CH4 inventory estimated each year by AEA Technology. However, generally speaking it is uncertain how to measure emissions, how to predict them, and how and when to influence them [P13 & 16]. An example of a specific knowledge gap is that not enough is known about emissions from closed landfill sites. It has been suggested that a survey should be carried out by the Environment Agency of such sites to identify the worst emitters and bring them fully into the monitoring and regulatory regime [P13].

Other influences on emissions Uncertainties relating to the impact and timing of mitigation measures (see WP3) affect all sectors. When incorporating the effects of mitigation into GCMs and other models, there is a need for gridded datasets. As stated above, there needs to be consideration of the feedbacks from the impacts and adaptations to the mitigation potential, to produce consistent storylines for adaptation and mitigation.

4.2 Concentrations

CO2 and the Carbon Cycle

There is a broad and general understanding of how the total amount of CO2 in the atmosphere is currently absorbed and the rate at which it is absorbed. There are still big gaps in the understanding of different reservoirs and of regional details. It is estimated that about 45% of

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CO2 emissions since 1750 has remained in the atmosphere, while about 30% has been taken up by the oceans and the remainder has been taken up by the terrestrial biosphere [1]. As for

the rate of absorption, it is estimated that about half of a CO2 pulse to the atmosphere is removed over a time scale of 30 years; a further 30% is removed within a few centuries; and the remaining 20% will typically stay in the atmosphere for many thousands of years [1]. However, many factors will affect the absorption processes and rates over time. For example, decreasing surface ocean pH and rising surface temperatures reduces the ocean buffer

capacity for CO2 and the rate at which the ocean can take up excess atmospheric CO2 [1]. Understanding these inter-relationships is therefore likely to be an area of ongoing research.

There is a moderate level of understanding of the link between the carbon cycle and CO2 emissions, as illustrated by some of the predictions being made. For example, based upon current understanding of climate-carbon cycle feedback, model studies suggest that, in order

to stabilise CO2 at 450 ppm, cumulative emissions in the 21st century could be reduced from a model average of approximately 670 GtC to approximately 490 GtC [1]. Current carbon cycle models agree that there is a decreasing capability for both the land and the ocean to draw

down CO2 as temperature increases. There are however large differences in the magnitude of this feedback between the different models. Existing observational data could be used to constrain the magnitude of the effect, looking at existing model outputs, at the level of individual processes. Specific uncertainties in key relationships include the following. • The magnitude of the positive feedback between climate change and the carbon cycle is

uncertain. This leads to uncertainty in the trajectory of CO2 emissions required to achieve a particular stabilization level of atmospheric CO2 concentration [1]. This is discussed further under WP1 above.

• Current CO2 emissions from agriculture and forestry have an error margin greater than 30-50% [365]. Great uncertainty exists on the long term ability of the earth to soak up carbon [P6, 4]. It depends on many factors including: • The sensitivity of carbon absorbing systems, such as forests, to future climate changes. • Direct human influences, such as clearing forests for agriculture. • The sensitivity of natural processes to the rate of increase and level of carbon dioxide in the atmosphere. For example, higher levels of carbon dioxide can stimulate a higher rate of absorption by vegetation (the carbon fertilisation effect) [4].

CH4

The abundance of CH4 (1774 ppb in 2005) is more than double its pre-industrial value [1] and it is believed that this is very likely due to anthropogenic activity [1]. However, since 1993 there has been a slow down in the growth rate. While it has been suggested that this is due to the atmosphere approaching an equilibrium during a period of near-constant total emissions

[1], the causes of recent changes in the growth rate of atmospheric CH4 are not well understood [1].

Ozone concentrations

The roles of different factors increasing tropospheric ozone concentrations since pre-industrial times are not well characterised [1].

Timing

It is not clear how fast the climate system reaches equilibrium. In particular the climate inertia, typically determined in simple climate models by the ocean mixing factors, is uncertain [5].

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These effects can however be quantified to some extent. Generally the timescale is 20-100 years for atmosphere and mixed layer, and 1000 years for deep ocean.

4.3 Overshoot

The discussion of overshooting is sometimes confused because it is not made clear whether what is being discussed is overshooting the concentration target (or targets), or a consequent overshoot of a temperature target. In what follows, we are referring to concentration overshooting, unless explicitly stated otherwise. There is a general view that if low targets are to be achieved then overshooting may well be unavoidable. It has been suggested to us, however, that there are two different views about what is achievable [R2]:

1. The Climate Change community’s view is that as stabilisation of concentrations of CO2 in

the atmosphere requires reduction of net anthropogenic emissions of CO2 to zero (over a number of centuries) then it is possible to overshoot concentration targets only by a small amount and then return to the target levels. The general view is that overshoots of 100s of ppm would require extremely efficient ‘negative’ emissions technology and that this does not appear credible in the next few decades. 2. A growing community of economic modellers are looking at peaking and overshoot scenarios that enable stabilisation at higher levels than are considered credible. There is a need to better understand: • the consequences of overshooting, • the assumptions used in models and the reasons for differences between models, • the feasibility and costs of returning to any given target level after an overshoot [R2, R3 & P6]. There is also the concern that leaving the door open for overshooting might be too tempting as it means significant costs can be deferred [P6].

‘Deliberate’ Overshoot

Overshoot scenarios can be divided into ‘accidental’ and ‘deliberate’. The accidental overshoots are recognised as undesirable. However there are those who argue that there would be benefits (in terms of not stressing economies too greatly in the shorter term) in having a deliberate concentration overshoot, which is then brought under control (i.e. concentration levels being brought down again by later mitigation measures) before a temperature overshoot could occur. While this is being pushed aggressively in some quarters, this is a risky strategy. To be able to respond to the advocates of this strategy, Defra should have an understanding of the associated risks (e.g. for use in the Copenhagen negotiations). This includes knowing the consequences of a small temperature overshoot (that is, if the strategy does not work perfectly) and the resiliancy against these. Even if the mean temperature does not overshoot (or at least not by very much), the probabilities of extreme events might be shifted significantly. One such event discussed by the group was a 10-year European drought. Another event mentioned more briefly was the commitment to the eventual melting of the Greenland ice sheet. A risk assessment on such events could be carried out using ensemble calculations on scenarios. This could (just) be done on the 2-year Copenhagen timescale, if the work was started promptly. Information relevant to such scenarios is coming out of university research. There needs to be a better mechanism for transferring this knowledge to the climate modellers – and also for the feedback of climate model needs to the researchers. There is pressure on NERC to make this happen – the mechanisms are in place but they need speeding up.

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In the WP3/WP4 syndicate session (March Workshop) Joanna House described a project that is examining the risks of overshoot involving a group that includes MOHC, Oxford and Manchester. The work could be completed on a year to 10 month timescale, but is behind schedule due to resource constraints. This project will not include examination of the impacts of overshoot on e.g. eco-systems or the risks of different type of irreversibility (e.g. loss of the amazon rain forest). In addition to this project, work has been carried out at the MOHC, and already reported to Defra, which considers a multi-gas framework. Also relevant is work by Myles Allen on total carbon amounts. These will help, but will not answer all of the questions, e.g. on system resiliency [R18]. When considering overshoots, it must however be remembered that to think that stabilised greenhouse gas concentrations imply a stable climate is a fundamental misconception. There will still be long timescale processes going on, with the consequence that all stabilisation scenarios overshoot a stable climate. The question is not how to avoid a dangerous

overshoot; we may already be at dangerous levels. For example, today’s CO2 levels might commit us to a 1 metre sea level rise, though we have know way of knowing for sure [R21]. The question is instead, how much more dangerous is any particular greenhouse gas overshoot. This depends not just on how large the overshoot is, but also for how long it endures. A small but persistent overshoot can lead to large cumulative impacts. For example,

suppose we ask: what will the effects be of an overshoot CO2 equivalent level of 550 ppm, above a target of 450 ppm? If the higher levels last only a decade, then the answer is not much. However a 30 year overshoot would put significantly more energy into the climate system [R21].

The idea of a ‘deliberate overshoot’ of CO2 concentrations, bringing the levels back down again before a temperature overshoot occurs, is therefore a dangerous one. Regardless of the

detailed risks, it will always be more cost-effective to stop the CO2 getting into the atmosphere in the first place, than to have to capture it again (e.g. by enhanced use of photosynthesis or by some form of sequestration [R21].

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5 WORK PACKAGE 3: POLICY OPTIONS AND TECHNOLOGICAL MEASURES

Key questions identified by Defra in this area include: 1. By how much can different sectors contribute to emissions reductions, now and in the future? b. What is the role of policy in enhancing abatement potential? 2. What are the costs associated with different stabilisation levels (i.e. marginal abatement costs), globally? As a function of: a. Share of reductions between different gases, sectors (including non-energy and land-use abatement decisions) and technologies employed b. The timing of emissions reductions c. The policies employed and timescale d. Assumptions (e.g. innovation) e. Market environment (e.g. fossil fuels prices) 3. What role can offsetting (i.e. carbon sinks) play in achieving stabilisation? 4. What policy instruments can help to achieve stabilisation most effectively? Including: a. Building a price for carbon (pros and cons of taxes and trading) b. Promoting technological innovation c. Removing barriers to action d. Engaging developing countries 5. What are the implications of stabilisation for competitiveness and structural changes to the economy? 6. What are the opportunities and co-benefits of mitigation? and from WP2 3. What are the implications of different multi-gas reduction strategies? c. Optimum balance between abatement of different gases, in terms of impacts and costs of abatement The research gaps and uncertainties relating to WP3 are a complex mix of technical feasibility, behavioural, political and economic issues. We have highlighted here a sample of issues raised in the interviews or secondary literature. Addressing many of these requires the use of energy-environment-economy models. Economic research needs are currently the subject of a separate detailed study, here the main focus is on identifying where the potential research programme can address gaps in the scientific and technical evidence base required to support economic studies. Economic modelling is considered in more detail under WP4. The figure illustrates the main topics examined under this work package and the relationship with other work packages.

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WP3: POLICY OPTIONS AND TECHNOLOGICAL MEASURES

technical/physical feasibility (of region, sectors, different gases, technologies, approaches WP5 WP5 to contribute to reduced emissions)

economic feasibility role of policy (GDP, demographics,…) (carbon pricing, promoting innovation, removing barriers, communication, engagement,…) political feasibility interactions with other policies and drivers

policy options to meet different stabilisation levels and pathways (reductions by region, sector, different gases, timing, technological measures, market instruments (carbon pricing),…) WP2 feasible market mitigation pathways response WP1 opportunities impact of policy scenarios costs of and co benefits options policy options of mitigation (timing, level,…) range of uncertainty (accounting for risks costs and benefits and uncertainties, of achievable levels impact of of stabilisation assumptions,… )

WP4

5.1 Global and Regional studies

While on a global scale the range of studies, sensitivity studies and model comparisons are considered to provide a sufficiently robust picture of mitigation costs and potential, there are gaps particularly for stringent stabilisation targets and in regional and country specific studies [WS]. In particular AR4 found that there were insufficient numbers of studies on low

stabilisation targets, such as 450ppmv and 400ppmv CO2e, to draw quantitative conclusions on ranges of costs of mitigation. In addition, the number of studies on mitigation costs, potentials and instruments for countries belonging to Economies in Transition and most developing regions is smaller than for developed and selected (major) developing countries [3]. Recent work by the team preparing studies for the UK-Japan Low-Carbon-Society (LCS) project will compare models at different regional scales in scenarios with the same carbon 4 price trajectories (reaching $US(2000) 100/tCO2e by 2050) . Current work by the EU ADAM

project (reporting May or June 2008) exploring the feasibility of achieving 400ppmv CO2e stabilisation should provide more studies on stringent targets. The ECOFYS top-down/bottom- up project (reporting May or June 2008) will advance the material presented in Chapter 11 WGIII of AR4 examining mitigation potentials at a broad regional and sectoral level. The regional breakdown will examine potentials at the OECD, developing countries and economies in transition level. All these projects will include model comparisons to 2030, 2050 and/or

4 Reported in a Special Issue of Climate Policy (to be published)

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2100 and will bring together top down, bottom up assessments. However, with the exception of the LCS project, they do not develop the analysis to the level of political regions. There are very few studies that do this and this makes it difficult to understand what policies individual countries would have to follow to achieve reductions. There is a need for country by country studies to identify the real actions that politicians will have to take and the real costs of these [EM] and to understand issues such as impacts on competitiveness, carbon leakage and spill-over [EM, WS]. Country by country studies of impacts, vulnerability, adaptation and mitigation have the advantage of being more meaningful to parties that will have to act. They can make the case for action more persuasively, help develop a shared understanding and support the design of policies to deliver necessary reductions [R19]. They can further support negotiations by demonstrating the potential for early action by developed nations to have positive spill-over benefits in terms of bringing on board developing nations [R19]. Use of quasi-experimental frameworks, including some common metrics, will facilitate aggregation, meta-analysis and generalisation [R14]. Such studies should be carried out in collaboration with experts from the countries involved and could not be completed within a short timescale or with limited resources [EM]. It is worth noting that many models were developed to assess the effects of the proposals for the Kyoto protocol in the period 1995-2005, and these were applied in studies, such as the EMF16 study

of the costs of Kyoto. These studies considered the 10-year and even 20-year effects of CO2 mitigation, but they are out of date (oil prices are currently many times those assumed for these studies and are expected to continue to be much higher than those assumed). Many of the century-scale models have also been extended to allow for multi-gas abatement in the

EMF21 study to include the Kyoto Protocol’s non-CO2 GHGs, The modelling capacity therefore exists to undertake new studies of GHG mitigation, although the costs and organisation of such studies should not be underestimated. The World Bank continues to do work in this area. This is an area where Defra could consider working with DfID to extend programmes such as the Précis programme to work with e.g. China, India and in the future in Africa.

5.2 Sectors

There are a range of sectoral models available, which when looking at short term mitigation become more country specific. There is also a lot of the work in the grey literature. A comprehensive review of recent advances in this work was beyond the scope of this study, but Chapters 4 to 10 in IPCC AR4 WG3 Report covers the sectoral literature, and could from the basis of a detailed review sector by sector of specific UK mitigation potentials to 2030. Interviewees identified a number of areas where particularly significant research gaps are believed to exist. These are described in the following sections. A key area of uncertainty across all sectors is the impact of the carbon market and other policies. These are described further under ‘Policy instruments’ below.

Short term mitigation measures and rapid reductions

In the short term it is important to understand the UK and global potential of those measures that can be safely implemented rapidly with today’s technology and which importantly may be realised as no-regrets options, as listed in IPCC AR4 Mitigation Report e.g. improvements in energy efficiency, use of biomass waste, avoided deforestation and how this can be realised [W/S]. Studies of the technical feasibility of quick down-wards trajectories and the impact of lock-in are an important area of research need. Research is urgently required to

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identify what needs to happen to move people from dependence on the fossil fuel economy: • Studies such as the Princeton Wedges5 study [Pacala and Socolow, 2004] help illustrate the actions that are needed to make required emissions reduction and break dependence on the fossil fuel economy. More studies of this nature are required delivering outputs in a form useful for policy making. This requires researchers and policy makers to work closely together to scope the study and define study outputs [EM].

• The literature includes a number of studies of how the US could reduce CO2 emissions of the order of 30% over 4-5 years [Barker and Ekins, 2004]. Some of these studies demonstrated a potential net benefit to the US. The models reporting these results could be used to look at rapid reductions in major OECD economies. • Research is urgently needed on the technical feasibility of really rapid reduction of emissions through home improvement measures within the context of current poor progress against the target on fuel poverty6, the regional problem of localised high unemployment and poor job prospects and the risk of recession in the construction sector. Much current policy rests on the assumption that big emissions savings are to be had at low or zero cost from measures such as better energy efficiency in homes, especially if a wider view is taken of potential savings in social security, health and other public spending. It is therefore important that this assumption is tested and that the financial, social or technical barriers to implementation are understood [P7]. • Similar research focused on commercial and government buildings could identify how price signals may be made more effective in redirecting new investment and retrofit towards low-GHG technologies, when new technologies and efficient practices are emerging from the market. • Many short term measures, including home efficiency measures, require individuals to take action. Much of the research need here relates to understanding behaviours, for example what are the barriers to individuals taking energy efficient measures (this is considered further under WP5)?

Long term mitigation measures and deep cuts

There are very few studies that explore the implications for sectors of actions required to

achieve longer term reductions and deep cuts (stabilisation at less than 450 ppm CO2e). There is a need for regional studies that look longer term beyond 2030. A gap that was identified and where work would be useful would be to review emissions projections, disaggregated by region, beyond 2030 [EM]. While projections to 2050 are used in, for example, the ETP model, it is not clear whether disaggregated projections are available and what the assumptions are used to derive these. If deep cuts are required (e.g. 60-90% relative to baseline), progress will need to be made in reducing emissions from industrial processes, aviation and a number of areas where it is currently hard to envisage cost-effective approaches [4]. Currently only a very limited number of studies have been carried out in this area [R3]. A very significant research gap is work that examines how deep reductions can be achieved and at what cost. There is an urgent need to understand the cost of deep reduction to 2020 and beyond.

5 The ‘Stabilization Wedges’ concept provides a simple framework for understanding both the carbon emissions cuts needed to avoid dramatic climate change and the tools already available to do so. See http://www.princeton.edu/wedges/ 6 Fuel poverty is where a household cannot afford to keep warm

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Costs of mitigation

The available estimates of global average costs of stabilisation vary. This is because there are significant differences in the assumptions used about baselines and mitigation options in the models and these assumptions have a major impact [3]. They may have a greater influence on costs than the final concentration stabilisation level [5]. Key areas of uncertainty include: • baseline trends, • effectiveness of policies, • flexibility of economies to adjust to higher energy prices, • the response of technology development and the impact of competition, and • assumed international policies [5]. While the range of studies, sensitivity studies and model comparisons are considered to provide a sufficiently robust picture of mitigation costs and potential at the global scale [EM], there are gaps particularly for stringent stabilisation targets and in regional and country specific studies (see above). Great uncertainty remains as to the costs of very deep reductions (60-80% or more relative to baseline). Timing issues are a major source of uncertainty including: • the rate of adoption of technology and induced technological change [3] • the impact of political and behavioural factors (see WP5), • the future economic, political and demographic landscape, and • the effects on cost of different regions mitigating at different times (and the consequent impact in terms of carbon leakage, spill-over etc). Another source of uncertainty is understanding the distribution of costs, benefits and disbenefits of a given policy or technology. As in other areas of research, definition of a more detailed picture of the world in 2020, 2050 etc to support analysis would be helpful [R19].

Benefits of mitigation

Climate change avoided AR4 (Technical Summary WGII) states that very few studies have been carried out to explore the damages avoided, or the impacts postponed, by reducing or stabilising emissions, despite the critical importance of this issue for policymakers. The few studies reviewed in WGII show the large reductions in damages that can be achieved by mitigating emissions [2]. Stern identified the considerable uncertainty over the benefits of mitigation as a barrier to action [4]. Work on describing and quantifying benefits should therefore help support mitigation negotiations. Uncertainties arise predicting: • mitigation potential (taking into account the technical, economic and political considerations including leakage and spill-over effects), • the impact of emissions reductions on climate variables and impacts (see WP1) • what would have happened in the absence of planned mitigation (BAU), and • the future economic, political and demographic landscape. Again there are significant uncertainties associated with timing. These arise both from the uncertainties associated with predicting when various mitigation options can be implemented and time lags in the climate and biophysical systems. These mean that global mitigation impacts will hardly be noticeable until around the middle of the 21st century [2].

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The biggest gaps in the research base identified are the assessment of co-benefits (see below) and the valuation of non-consumption damages. The latter is discussed under WP4.

Co-benefits Many recent studies have demonstrated significant benefits of carbon-mitigation strategies on human health, mainly because they also reduce other airborne emissions improving air

quality. There are also expected to be considerable benefits for agriculture (low-level O3 reduces crop productivity) and a range of other co-benefits. The impact of co-benefits will vary from region to region and could be particularly significant for developing countries. However inclusion and treatment of co-benefits in economic models of climate change and mitigation remains controversial. Co-benefits were identified as one of the most important priorities for research in particular the benefits to health and agriculture of improved air quality [ES, W/S]. The issues raised include: • quantification of co-benefits – there have been many studies but not necessarily at the regional breakdowns or under the scenarios required by policy makers, nevertheless there has been sufficient quantification to enable the potential impact of co-benefits to be explored • methods for inclusion in economic modelling. Inclusion of co-benefits in economic models is discussed further under WP4.

Technology and rates of adoption of technology

While the importance of technology to climate change is widely understood and our understanding of its role in addressing climate change is improving continuously, there are differing viewpoints on both the feasibility of current technology to address climate change and the role of new technology [3, R15]. Perhaps 80-90% of low carbon technology development to-date has been aimed at electricity generation. A key challenge will be finding low carbon alternatives to other major emissions areas. There is a continued need for a better understanding of how rates of adoption of climate- mitigation technologies are related to national and regional climate and non-climate policies, market mechanisms (investments, changing consumer preferences), human behaviour and technology evolution, change in production systems, trade and finance and institutional arrangements [P19, 3]. There is also a need to understand the inter-dependencies of portfolios of technologies, and cross-enhancement (‘spillover’) potentials. The factors effecting adoption of technology and the processes by which technologies are created, developed, deployed and eventually replaced are complex and no simple descriptions of these processes exist [3]. The learning process for new technologies is uncertain [4]. It is also highly uncertain to what extent technologies will be adopted even in a world that has no focus on carbon [5]. A key issue is how much does technological change respond to climate policies, e.g. a reliable carbon price. Research into these issues can support: ƒ Modelling of mitigation costs and potential and inclusion of technological development in economic models. The biggest gap relating to technology was considered the way it is handled in most shorter-term economic models [EM] – this is discussed under WP4 below. ƒ Identification of the technology pathways required for different stabilisation levels - IEA are currently studying technology pathways through to 2050, this research is due out in June/July. ƒ The design of policies to promote technological development and change (see under ‘Policy instruments’ below).

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Sector specific issues

Because this is a rapidly developing area, it is not easy to single out which packages of work in specific sectors, will be most beneficial. A comprehensive review of the academic research and grey literature to establish what has been studied, the level of certainty that can be ascribed to the findings, and how they can be verified is beyond the scope of this study. However, a useful way of identifying key gaps in the technical research base for the UK could be to use UK costs of abatement for specific technologies, as available in the UKERC’s 2007 MARKAL study for BERR, as a starting point [WS]. We understand that Defra are currently working to verify the global costs from the McKinsey version of this approach. This process should be used to identify gaps, uncertainties and areas where additional work, on academic timescales and with academic rigour, will be most useful in the context of this research programme. Chapters 4 to 10 in IPCC AR4 WGIII Report covers the sectoral literature, and could form the basis of a detailed review sector by sector of specific UK mitigation potentials to 2030. A number of specific areas of research need were identified. These are described below.

Biomass and trade-offs

Biomass potentials could be large e.g. burning biomass in CCS plant can remove CO2 from the atmosphere, but implementation of a mitigation potential based on biomass may compete with other activities. For example there may be trade-offs with food production, forestry or nature conservation [3]. However, biomass may also complement other activities in that energy crops may help stabilise land surface, retain and purify water and support biodiversity and bird life. The extent to which the biomass potential can be realised over time is still poorly understood [3]. This has been identified as an area where work is required to confirm potential: to identify for example where biomass could be grown profitably, what the water needs are, what the impact of climate change is likely to be on these, and economically what the impact on food costs etc will be [EM]. It would require collaboration between climate scientists, forestry/agricultural and impact specialists and economists. This was considered a very important piece of work both because of the potential contribution that bio-mass could make to reductions and because of the potential scale of the global damage that could result from inappropriate policies. This would be a significant research project.

Aviation and shipping Barriers to affecting change in the aviation and shipping industries include technical constraints, long lead times and business planning constraints and regulatory issues and international agreements. While potential solutions exist (e.g. carbon capping) their consideration and implementation is believed to be constrained by difficulty demonstrating the impact of these sectors on climate change. A small but useful piece of work would be to run current estimates and predictions of global aviation (and shipping) emissions through the MOHC atmospheric chemistry and climate models. This would be a short piece of work (6 month to a year) and would help clarify the potential impact of aviation and shipping [EM].

Agriculture, forestry and off-setting Deforestation and agriculture are such big emitters of greenhouse gases that any significant mitigation programme needs to include them. They are therefore an important area for research. Realisation of the mitigation potential of forests requires institutional capacity, investment capital, technology, R&D and transfer, as well as appropriate (international) policies and incentives [3]. Uncertainties in the carbon cycle, the uncertain impacts of climate change on

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forests and its many dynamic feedbacks, time-lags in the emission-sequestration processes, as well as uncertainties in future socio-economic paths (e.g. to what extent deforestation can be substantially reduced in the coming decades) cause large variations in future carbon balance projections for forests [3]. Developing optimum regional strategies for climate change mitigation involving forests will require analysis of the trade-offs (synergies and competition) in land-use between forestry and other land-uses [3] and consideration of important social and cultural issues. For example it is possible to protect the rainforest by providing property rights for native people but as the prosperity of native peoples increases so will their carbon usage unless this solution is implemented as part of a package that moves the whole economy to a low carbon basis. While this was identified as a very important area for research by many interviewees, there is a lot of work currently on-going, for example the Eliash review, and it was not considered a priority area for this programme. More research is required to reduce uncertainty relating to the carbon cycle. This is discussed further under WP1.

Other sector specific issues The literature and our interviews identify a very wide range of other uncertainties and gaps in the knowledge base relating to difficulties identifying and implementing mitigation measures and assessing their costs and benefits. The types of issue raised are summarised in the box overleaf. Verification of the UK McKinsey MAC curves could be used to identify specific work packages in these areas as suggested above.

5.3 Geo-engineering options

Geo-engineering options include direct radiative measures e.g. blocking sunlight by bringing

material into the upper atmosphere, or indirect e.g. ocean fertilization to remove CO2 directly from the atmosphere. Some of these would be possible with today’s technology. Others are more speculative and unproven, and with the risk of unknown side-effects [3]. It is important to explore the potential of these measures and the timescales to adoption, and also to understand what assumptions are currently being made in economic modelling of mitigation with respect to these technologies and to test the feasibility of these [W/S].

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Other Sector Specific Issues Raised Energy: Specific issues raised include: • Technical development and change: ƒ How quickly are e.g. new coal plants going to be equipped with CCS (Carbon Capture and Storage) technology, what impact will additional costs have on demand? ƒ How can mitigation be achieved for distributed domestic heating systems when most domestic heating systems rely on natural gas [R12]? ƒ What role can standards and planning laws play in encouraging or requiring adoption of existing technologies (e.g. CCS and combined heat and power plants) was also raised as an issue (see below). ƒ Will a change to biomass for energy help to reduce problems associated with increased risk of flooding? • Impact of climate change: How valid will renewables be in a changed climate (e.g. what is the effect of shift of storm track on wind power in Scotland [R19])? • Understanding societal attitudes: e.g. what will drive the social acceptability of large-scale use of nuclear power? [5]. Societal attitudes and behaviours are considered in more detail under WP5. Transport: Issues raised include: • Technical issues: for example assessing how people’s need for mobility can be satisfied in a low carbon way and the mitigation potential for heavy-duty vehicles • Behavioural issues: it is, for example, not clear how effective policies can be in shifting passengers from cars to buses and rail or other low carbon solutions [3] (see WP5) Heavy manufacturing industry: How can reductions be made particularly in steel and concrete

production where the inherent chemical processes used are major emitters of CO2 as part of the oxidation/ reduction process. Some of these technologies are particularly well suited for carbon capture, however, pricing has to be in place to make this happen.

5.4 Policy instruments

Policy instruments can help to achieve stabilisation in a number of different ways including: 1. Building a price for carbon 2. Promoting technological innovation 3. Promoting informed choice 4. Removing barriers to action 5. Engaging developing countries

More work is required evaluating the success of different policy instruments and learning from experiences of other countries [P20].

Building a price for carbon To achieve a global carbon market the UK envisions having a series of stepping stones – the key question is what do we need to do to get from one to the next? A wide range of areas of particular uncertainty or research need were identified (see box). The key challenge is how to arrive at a reliable, stable price for carbon in the longer term that will effect emissions. There are concerns that the price in the ETS doesn’t appear to be very stable, nor high enough to effect businesses that use high discount rates (short payback periods). There is a concern that this will still be the case for Phase II. The existence of the market after 2012 will have a critical effect on price.

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There is currently a lot of work on-going in this area. Areas suggested where this programme could usefully contribute were:

• Studies using up to €100/tCO2e for the carbon price to estimate the economic costs to Europe of more stringent EU-wide targets of emission reduction by 2020. This would give an indication of the costs and impact on emissions of the 30% target and any more stringent target that may be suggested in international negotiations. Much modelling work has been done, mainly in projects and studies for the European Commission in preparing for the EU ETS, but again they have become out of date, not least because of higher oil, gas and coal prices. Recent studies [Entech] for Phase2 of the ETS involving auctioning of allowances could readily be scaled up to assess the effects of a range of allowance prices • Ongoing review of the impact of the Kyoto Clean Development Mechanism (CDM) and EU Emissions Trading Scheme (ETS), to provide evidence that such schemes can work.

Questions and issues raised relating to the Carbon Market • What sectors should be included in schemes, and how (with the focus on practical approaches rather than theoretical)? • What control mechanism is appropriate? Where there is uncertainty in the timing and scale of impacts, as well as in the costs of abatement, control by a price mechanism (i.e. a tax on emissions) and controls on quantity (i.e. setting emission quotas) would be equivalent in terms of their cost efficiency. However the presence of uncertainty means this is no longer the case and the mechanism selected must be chosen with care. • How can prices, caps, benchmarks or allocations be established such that:

ƒ the necessary reduction in CO2 emissions is delivered via market forces? ƒ some operators are not inappropriately disadvantaged, companies don’t accrue inappropriate windfall profits and perverse behaviours are avoided [P13]? • Are there mechanisms for managing and if possible avoiding unintended consequences, e.g. by retaining a substantial percentage of the allowances to manage the market? • What is the potential role of ‘revenue recycling’, especially to provide financial incentives for reducing barriers and encouraging low-GHG innovation [P13]? • How can permit prices consistent with trading schemes be established where these must be based on estimates of future emissions rather than actual emissions [4]?

• How can allocation levels for non CO2 GHGs be established [4, P13, R11]? • How can the issues surrounding forestry and de-forestation be included in the global carbon market [P3]? • How can less tangible benefits such as increased bio-diversity be included in the carbon market? • What effect will high permit prices have on e.g. EU competitiveness, carbon leakage and spill- over [P16]? • What are the appropriate carbon market mechanisms for middle/low income countries [P3]? What is the correct mix of CDM, sectoral emissions trading, and discounting to encourage their participation [P3]?

Promoting technological innovation and take up of technologies Unless policies can successfully stimulate development and transfer of technology it may be difficult to achieve emission reductions on a significant scale [3]. Mechanisms to scale up technologies and make them commercially viable must be in place. The right balance between

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market push and pull must be achieved [P6] and barriers to adoption of cost-effective, low- GHG emission technologies must be reduced. Key areas of uncertainty suggested are: • The innovation chain: The innovation chain appears to be different for each technology type, so the dip in funding between Government R&D and industry taking it on occurs at different places. A key question is how can mechanisms to address this be made to work more efficiently [P6]? • Emerging technologies: More work may be needed on how to how to promote innovative thinking and horizon scanning to identify key technologies for the longer term (2050 and beyond) [R15, W/S]. However this is not something that should impact Defra’s negotiations or thinking on stabilisation at this stage. This could be a study to feed into ETSA’s [?] programme. • Barriers to take-up: Businesses operate under a complex range of commercial and legislative drivers some of which will present considerable barriers to take-up of low carbon solutions. Key requirements are for regulatory stability and availability of funding. Uncertainties concerning carbon prices (see above) and funding will present barriers to adoption of technology [W/S]. It is not always clear what the barriers to take-up of new technologies are and what policy levers can be used to address these effectively in specific instances. For example what are the barriers and incentives to people who generate their own electricity to sell surplus power back to the grid [P13]? Regulations and planning laws can provide one method of driving adoption of technologies. For example by requiring that hot-water grids with Combined Heat and Power (CHP) are considered (or even included) when building new towns (with energy from waste plants or flood-plain biomass). If local pollution is seen as a problem, then CCS in closed-loop power generation may be a further option. Such requirements are not currently mandated in the UK. In this area the need is not for more analysis, but to review and update planning law, standards etc [P13]. There are several models of technology development and a review and comparison of these may be useful as could a review of approaches adopted internationally to promote technology adoption. • Portfolio assessment: It will be necessary to identify ensembles, or portfolios of technologies. These will have inter-dependencies and cross-enhancement (‘spillover’) potentials. This adds another element of uncertainty into any analysis [3]. A number of programmes of work address technology development and adoption with DIUS and BERR having lead responsibility in the UK. The biggest gap identified relates to the treatment of technology adoption and learning rates in economic models (see WP4).

Communication and promotion of informed choice Information instruments (e.g. awareness campaigns) may positively affect environmental quality by promoting informed choices and possibly contributing to behavioural change, however, their impact on emissions has not been measured yet [3]. Customers need confidence in the information they are given about the environmental impact of different products and services [11]. There has been little work done on the potential impact of the voluntary market and measures such as carbon signalling and information and how these can be promoted and regulated [R23]. The savings here may be substantial and this is therefore an important gap. This is discussed further under WP5.

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Removing barriers/managing risks Key areas of research identified include: • Research into the actions required to break dependence on the fossil fuel economy was seen as being the highest priority (see under ‘short term mitigation’ above). Studies similar to the ‘Wedges’ study, were suggested as one way of making the issues clear for policy makers [EM]. • Research into loss of competitiveness risks (e.g. EU/US, Eastern Europe/Russia) and how these can be most effectively managed (e.g. though global technological agreements and standards). The aim would be to understand what policy responses will help minimise carbon leakage. OCC are addressing this via the Glocaf model [P19]. • A major barrier for businesses to investing in low carbon solutions is lack of long term stability, for example long term commitment (20 plus years) to the Kyoto CDM and the complexity and timescales involved gaining approval. • A major knowledge gap is the lack of studies looking at identifying and managing perverse behaviours and unintended outcomes resulting from policy interventions. It is important in this context to differentiate between behaviours that are a result of a policy operating as intended, but which may be seen as perverse (for example companies accruing significant ‘windfall’ profits from trading access allocations) and genuinely perverse behaviours (e.g. companies pursuing hi-carbon options now in order to ensure that any carbon allocation imposed in the future is easily managed). The former is undesirable in that it may result in bad publicity and undermine the reputation of the policy. This is considered further under WP5.

Engaging developing countries Developing countries face particular economic challenges. Investment in energy is insufficient to support economic growth; most comes from development agencies rather than the private sector. It is not clear how to stimulate short term financing for medium to long term issues, how to mobilise private sector funding for reduced carbon energy, or how to overcome governance issues that represents an investment risk in politically unstable countries [P9]. A key area of research need identified is improving understanding of the interdependence and interaction of sustainable development and climate change, linkages between mitigation, adaptation and sustainable development and, more particularly, on how to capture synergies and minimise tradeoffs [3, W/S]. DfID is currently working jointly with NERC on climate change and poverty alleviation. Specific areas where additional work was suggested are: • Mechanisms to encourage transfer of technology developing countries including encouraging investment for reduced carbon energy and tackling governance issues [P9] A specific issue raised was how to ensure that investment in developing countries is well targeted, given the uncertainties associated with predicting the timing of climate change impacts and the other challenges faced by these countries. Implementation of blanket climate proofing requirements can hinder cost-effective development and adaptation [R7]. • Appropriate carbon market mechanisms for middle/low income countries to encourage their participation [P3] • Sustaining development while mitigating climate change [P10, W/S] • Impact of information provision on low carbon and sustainable agriculture approaches.

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6 WORK PACKAGE 4: LONG TERM TARGETS

The United Nations Framework Convention on Climate Change (UNFCCC) commits both developed countries and developing countries to work towards the stabilisation of greenhouse gas concentrations in the atmosphere at levels that would prevent dangerous anthropogenic interference with the climate system. This stabilisation level remains undefined in international negotiations. The EU is the only region to have set a long-term goal so far; agreeing a target to keep global mean temperatures at not more than 2°C above pre-industrial levels. A long-term goal can be defined in many ways, most commonly a temperature target, GHG stabilisation level or emissions reduction. These different definitions are all equivalent (although the actual equivalences are uncertain), and correspond to a set of actions and consequences (impacts) depending on the level of the goal. Work Packages 1 to 3, and 5, will examine the link between different stabilisation levels, actions and consequences, and behavioural aspects of stabilisation. This Work Package will assess the evidence which draws on these areas to propose a long-term goal for international policy. The research gaps and uncertainties relating to WP4 have been discussed under the main headings: • Setting targets • Decision support approaches • Facilitating agreement • Implications of targets.

The figure illustrates the main topics examined under the three areas and the relationship with other work packages.

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WP4: LONG TERM TARGETS

WP3 feasible levels WP5 of stabilisation pro’s and con’s of different WP5 dangerous types of long term goals climate change WP1

WP2 benefits/risks/costs of different targets and pathways decision making WP3 approaches

action required to maintain temperatures below 20C above pre-industrial range of uncertainty (accounting for risks and uncertainties, impact of assumptions,… ) facilitating implications agreement for e.g. adaptation

WP5

Key questions identified by Defra in this area include: 1. What level of climate change should be avoided? 2. What level of stabilisation looks feasible? Given the current GHG level, available technologies, regional circumstances, costs, political inertia etc. 3. What is the optimum balance between the costs of mitigation and the risks of climate change impacts? a. Sensitivity to assumptions about mitigation and impacts costs, adaptive capacity, discounting and equity. b. Accounting for risks and uncertainties 4. What are the pros and cons of different types of long-term goals? 5. What is the appropriate social cost of carbon? 6. What action is required to maintain global temperatures below 2°C (above pre- industrial)? a. What are the risks? b. Is overshooting a viable option in terms of risks and feasibility? c. What are the implications for adaptation? 7. How can we best facilitate an international agreement on a long-term goal?

6.1 Setting targets

Establishing the appropriate level at which to set long term (and intermediate) goals involves answering the following questions: • What constitutes ‘dangerous anthropogenic interference’ with the climate system? • How can this be translated into targets, in particular: ƒ On what types of measure (metrics) should targets be set? ƒ At what level must the target be set to avoid ‘dangerous interference’?

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ƒ What are the feasible pathways to meet this target? ƒ What are the residual risks associated with these targets and pathways – are these acceptable? • How should global targets be allocated between Annex I and II countries and to the UK (burden sharing)?

Defining dangerous interference

There is still significant debate about what constitutes a dangerous level of climate change that should be avoided [5], questions to be answered include: • What impacts are relevant to policy making [5]? • What scale of impacts are of relevance: ƒ global scale impacts, such as disintegration of the WAIS [5]? ƒ impacts that while more limited in immediate effect, might have global importance, such as destruction of a valuable ecosystem [5]? ƒ impacts at a finer scale, perhaps to limited geographic impacts which may only be of high importance to a region, country, province, or even a village [5]? • How can impacts be measured [5]? • To what extent is it possible or desirable to aggregate different kinds of impacts under a common metric [5]? What may be considered as ‘dangerous’ (including how vulnerability should be characterised) is one of the central, unresolved and contentious, questions in the climate change debate [5]. The climate science is now well developed, relevant research gaps in this area are discussed under WP1. Any consideration of what constitutes dangerous’ interference however raises questions about values that may differ depending on the region and context. It is necessarily a social and political judgement [3] as well as a scientific one [5]. A key gap is a framework within which this value judgements can be discussed [EM]. This is discussed further under WP5. In terms of identifying ‘dangerous’ levels of climate change and establishing long term goals set on stabilisation levels, it is not necessary to place a monetary value on intangible impacts if a risk based approach is adopted. In this case it may be sufficient to paint a picture of the risks without specifically valuing the communities or eco-systems under threat. It is enough to agree that specific impacts are things that we (as a global community) wish to avoid and to determine the e.g. concentration trajectories that reduce the risks to an agreed tolerable level. However some method of including such impacts in economic models or other decision support tools is required to establish e.g. how to achieve goals most efficiently or how limited adaptation funding should be spent. Valuing benefits is discussed further below.

Types of measure

Different types of long term goal will have different benefits and disbenefits. The appropriateness of the environmental standards approach - The objective stated in the United Nations Framework Convention on Climate Change (i.e. to achieve stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system) essentially implies an environmental standards approach. There is concern that this approach, which requires a large amount of impacts knowledge to be well circumscribed and certain before preventative or precautionary action can be justified, may have created more obstacles for climate policy than might otherwise have existed [5]. Concerns were raised by interviewees that the concept of stabilisation and what it means had been insufficiently discussed in society.

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Choice of target metric - Vulnerability results from a complex interplay of hazard, exposure and adaptive capacity. This makes it difficult to draw direct correspondences between levels or rates of climate change and outcomes that matter. The links between levels or rates of change of GHG concentrations or emissions and outcomes are even more difficult to make. It is not possible to say with a high degree of confidence that, for example, stabilisation of o concentrations 450ppm C02e will achieve a 2 C warming, which in turn will result in a stable climate [P9, R10] (see also WP1 and 2). Non-linearities introduced by thresholds, feedbacks and extremes introduce further complications and are poorly understood (see WP1). Using temperature change as the basis for a target has the advantage of being more closely related to the types of impacts and outcomes we are aiming to avoid. Using concentration levels is more practical, as these can be measured more directly. However lags in the climate system means that it takes many years for changes in emissions to be translated into a stable atmospheric concentration. While debate continues about what constitutes the best metric, in terms of current negotiations the issue of what metric to use is largely settled [EM], so this is not a priority area for the proposed research programme. The University of Oxford are, however, currently working on a tool that allows estimation of the highest global mean temperature associated with total emissions, integrated to 2030. Targets can be set in terms of total integrated emissions. Economists are thinking in terms of this now. This concept may help in the pricing of carbon, providing a link to carbon budgets and helping develop long term policy. This may be of interest to policy makers [W/S]. Multi-gas reduction strategies – A given level of global warming could occur through different combinations of GHG concentration increases and climate sensitivity. For example

high levels of CO2 and low CH4, or lower levels of CO2 and high CH4 will give the same global warming but will have different impacts on things that are affected by the other impacts of

CO2. The issue is relevant to multi-gas abatement options and target setting - cutting say

methane and comparing it with CO2 in terms of radiative forcing or GWPs, would not properly

reflect the relative impacts as methane does not exert the same additional impacts as CO2 [R11] – such as fertilisation and ocean acidification. This is not however a science gap. The science exists to equivalence gases, but the way you do this depends on the nature of the application and particularly the timescales of interest. If policy makers want to set targets, or trade, across a basket of gases then science can provide the answers. A briefing paper setting out clearly the importance of timescales and their impact on different gases could be useful [W/S].

Level of target and pathways

Because of the many uncertainties, a sound evidence base for current targets has yet to be established. Questions to answer include: • Is a 60% reduction in emissions by 2050 appropriate? • What would this mean for targets in 2020 [P1]? • Will this limit the temperature rise to 2oC above pre-industrial levels, what is the risk that this will be exceeded, what are the risks if it is? • What are the residual risks in human welfare terms if targets are met? While there are concerns about the impact of making overly expensive reductions on the economy and the feasibility of making continuing cuts into the future, there are also serious concerns about the feasibility of avoiding dangerous climate change if action on mitigation is delayed [P5, 5, 3, 11]. There is a good picture of the possible pathways to meet targets but there is much less useful information on how feasible these are, i.e. which ones are achievable from a technical, economic and political point of view [P7]? The level, timing and cost of achievable reductions are all uncertain (see WP2 and 3). The implication of

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overshooting concentration targets is also unclear. The general view of climate scientists appears however to be that only very small overshoots can be accommodated if targets are to be achieved (see WP2). The Adair Turner review is currently on-going in Defra. This work, we understand, will start from definition of a set of feasible global emissions pathways to establish a long term goal for the UK, it will examine, among other things, the risks of exceeding a range of specific global mean temperatures (2oC, 3oC etc). It is to report in December. Currently it is not clear what research gaps this work will reveal. A particularly useful function for the proposed research programme would be if it could deliver the capacity to provide short term policy relevant support to provide answers to questions as they arise [W/S].

Regional targets/Burden sharing The issue here is how to divide emissions limits up amongst the peoples of the globe. Different approaches have different impacts on global economic development, issues of equity and justice. There is a need for agreed methods for determining burden sharing [R3] and to establish whether regional or country targets can be linked effectively with development goals e.g. millennium goals [P11]? A lot of work is however ongoing in this area and this is not seen as a critical gap for this programme. A meta-review of the literature may be useful.

6.2 Decision-support approaches

Challenges

Challenges to decision-making arise from: 1. The range of uncertainties including: a. Climate science: There are a large, and to some extent unknown, uncertainties in predicting climate changes. These have been the subject of considerable research effort for many years and therefore it must be accepted that decisions about mitigation must be made in the face of considerable scientific uncertainty (WP1, 2) b. Inherent variability in the climate system: The climate system is inherently variable complicating measurement of climate changes, prediction of changes due to anthropogenic affects, and the recognition of climate change signals by individuals, organisations and governments (WP1) c. Socio-economic uncertainties in an increasingly climate constrained world (WP1) d. Uncertainties in the costs and benefits of adaptation and mitigation options and the timing of mitigation (see WP3). 2. Lags in the system including: a. Climate lags: observable changes in climate trail years behind changes in emissions (WP1, 2) b. Political inertia: it can take a long time for countries and organisations to make and implement decisions (WP3) c. Knowledge development: improved scientific understanding, better observations, emerging technologies 3. The distributive and diverse nature of the costs and benefits: a. the need to make difficult trade-offs in some areas [3] b. the difficulty valuing impacts on natural systems and human health that do not have a market value, and for which all approaches are simplifications of the reality [3]

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There are also a number of practical considerations related to the decision making and negotiation processes: 1. In economic theory it is possible to construct graphs which suggest that adaptation and mitigation are alternatives and that a balance of the two would form an optimum strategy. However, decisions about adaptation and mitigation are made by different players in different jurisdictions, and there is no authority that can choose how much of each is to be deployed [5]. 2. In theory, under special assumptions and conditions, it is also possible to identify through economic analysis the optimum level of mitigation that balances costs and benefits. However, climate change presents such large systemic risks that the problem is seen as even by economists as no longer one of cost benefit optimisation but of risk management. 3. There are significant problems identifying, measuring and quantifying the many variables that are important inputs to any decision support analysis framework [3]. Models and analyses, especially at the global scale, tend to get ‘bogged down’ in the detail [R19]. 4. Agreement has to be reached between people with different value systems, drivers etc [3]. Decision and target setting processes are needed that recognise the uncertainties, take into account the lags in the system, and reflect the realities of the negotiation processes. Methods are required that can help develop a clearer picture and a shared understanding of what needs to be achieved, and what this means in terms of action at the regional, and (locally) at the sectoral level. Processes should allow targets and agreements to be regularly revisited as uncertainties are resolved or narrowed [P11].

Economic analysis

Economic modelling is central to understanding among other things: • Mitigation costs and potential globally and by sector, region and country • Impacts (and avoided impacts) of climate change (BAU and mitigation scenarios) on the global, regional and national economies • Competiveness, carbon leakage and spill-over effects. They are used for estimating parameters such as the social cost of carbon that are used in cost benefit analyses to support policy decision making. Both top down and bottom-up approaches are adopted.

Top-down analysis Top-down Integrated Assessment Models (IAMs) link aggregative economic growth with simple reduced-form climate models to analyse numerically the economic impacts of global climate change. IAMs have proved useful for understanding some aspects of the economics of climate change especially in describing outcomes from a complicated interplay of the long lags and big inertias that are involved. However where radically different paths have to be compared, where risk and uncertainty are of the essence, and where many economic, social and scientific features are poorly understood, simplified IAMs risk either confusing issues or throwing out crucial features of the problem [Stern 2008]. More complex top down, structural models and analyses that attempt to account for a wide range of variables, especially at the global scale, can get ‘bogged down’ in the detail [R19].

Bottom-up analysis Bottom-up analyses examine costs and potential at the individual sector level to build up a picture of mitigation potential and costs. The available studies of mitigation potentials and costs however differ in the methods adopted and do not cover all sectors, GHGs or countries;

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because of different assumptions, for example with respect to the baseline and definitions of potentials and costs, their comparability is often limited [3]. Comparison of costs and mitigation potentials based on bottom-up data from sectoral analyses with top-down costs and potential data from integrated models shows that the match at the sectoral level is limited. Lack of or incomplete data from bottom-up studies and differences in sector definitions and baseline assumptions however make comparison difficult. Current work being undertaken by ECOFYS will compare top-down and bottom-up approaches and should help to clarify this issue. This study will provide results at the regional level (OECD, EIT and developing countries) but not at the country level.

The risk evaluation approach The levels of scientific and inherent uncertainty, the large potential impacts, and the multiple dimensions to be taken into consideration when establishing appropriate levels of action, suggest a risk assessment based approach is appropriate. A risk management or 'hedging' approach can assist policy-makers to bring forward mitigation decisions, even in the absence of a long-term target, taking account of the large uncertainties related to the cost of mitigation, the efficacy of adaptation and the potentially very significant negative impacts of climate change [3]. A risk based approach involves working out what matters to people and presenting information for decision makers in terms of the likelihood of this happening under different scenarios [P11] including different adaptation and mitigation scenarios. Modellers are increasingly able to present outputs in probabilistic form. For example current MOHC work for Defra feeding into the Adair Turner review is providing probability distribution functions and estimates for each of a range of specific temperature rises (2oC, 3oC etc) and emissions scenarios: • the probability of not exceeding the temperature, • the probability of exceeding the temperature, but returning to the temperature, • the probability of exceeding the temperature and not returning. Targets are set by reference to the risks and economic models can then be used to determine the most cost efficient way of reaching the target (rather than establishing the target level through cost-benefit optimisation). This is the approach recommended by Stern. Because of the potentially very high damages of climate change low-probability, high- consequence events must be included fully and formally in economic impact models. Most existing economic analyses of climate change treat central forecasts of damages as if they were certain and then do some sensitivity analysis on parameter values. They rarely incorporate uncertainty at all into the structure and when they do often truncate PDFs at arbitrary cut-offs. We understand that it is this failure to account properly for the shape of the distributions that accounts for some of the difference between Stern’s results and that of traditional economists (as well as the approach to discounting he adopted, which has been the cause of much debate). Recent work by Weitzman [Weitzman 2007] developed a method to include PDFs more fully in the economic analysis [P19], but this is still not a fully risk based approach. However he agreed with Stern that much earlier action was justified once risk is accounted for in models and argued for greater emphasis on risk and uncertainty. Finally we understand that the PAGE model, used for the Stern Review, has been revised further to explore the implications of the assumptions about discount rates used in its application reported in the Review. This is a risk-based model that captures the cascade of risks from emission to impact and adaptation.

Comparison of approaches While there is a role for each of the different types of model and approach, provided the limitations of the model given the particular characteristics of climate change are fully recognised, we believe that much more emphasis needs to be placed on the risk based

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approach and the use of methods and models that fully account for risk and uncertainty in the analysis. We consider this a critical gap. Stern in his recent paper [Stern 2008] emphasises that he considers bottom-up, dis- aggregated, less formal, risk-evaluation approaches much more useful aids to decision making, and for investigating the case for action, than aggregated models. Weaknesses common to most models and modelling approaches include: • underestimation of the impact of BAU climate change • the treatment of less tangible benefits and dis-benefits (health impacts for example, where included, are often combined with consumption damages and discounted at the same rate) • the treatment of health and crop-productivity co-benefits of mitigation • treatment of induced technological change • lack of agreement on discounting and the treatment of ethical issues in models • lack of country specific studies (see WP3). A significant difficulty is that there are different schools of thought with respect to economics with the EMF taking a more traditional approach to, for example, induced technological change and co-benefits, than is considered appropriate by many in the UK [EM]. We have identified a number of key research needs relating to these issues. They are discussed in the next section.

Key Research needs

A wide range of issues were raised by interviewees, these are summarised in the box below. As economic research needs are currently subject to a separate detailed review we have focussed on indentifying research needs related to the key issues identified above in the rest of this section.

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Economic Research: Issues raised during this scoping study include: Modelling • Adoption of risk-based approaches • Developing methodologies that can account for low-probability, high-consequence events in economic impact models • Improved modelling of impacts to support integrated modelling: economists and the impacts’ community need to work together to achieve this [P9] • Methods to include health and other goods with intrinsic values in models • Linking of IAMs to more complex climate change models [R16] • More work building on the dynamic economic modelling now being carried out, exploring for example the rate of adoption of technology in an environment where stabilisation hasn’t been achieved, looking dynamically at how mitigation can be managed over time [R16] • inclusion of induced technological change in models [8, W/S, EM] • Improved treatment of autonomous and planned adaptation - understanding the level of investment required and the time period and scale of benefits [P9]

• Inclusion of non-CO2 greenhouse gases in models – these are in some of the European models Parameters and parameterisation Further discussion and exploration is required of: • how equity should be handled in models [P9], • how to define appropriate global welfare functions [5], • how to include such factors as how people care about climate change in the discount rate [P18] and • how to resolve the issues of social choice lying behind these uncertainties [4] • How equity etc should be considered in relation to ‘contraction and convergence’ proposals [R20]. • how to handle risk aversion, especially the conflict between risk aversion about climate change at the national scale, which is prompting early action, and risk aversion at the sector and industry level, which suggests a more cautious approach based on risks to e.g. competitiveness [R19] • how to value environmental and health impacts including long term bio-diversity, the preservation of ecosystems, environmental services etc [P10, 5] • review of assumptions on emissions pathways (including overshoot pathways) included in economic models: role of emerging technologies, the potential from geo-technical measures etc • review of assumptions relating to behaviour of individuals and societies in models (WP5) Studies • Use of a wider range of models to look at alternative emissions trajectories [P2] • More extensive model comparisons: The Stanford Energy Modeling Forum (EMF) has focused on Computable General Equilibrium Models, more work is needed comparing these models with e.g. non-equilibrium models [P9] A need for a broader modelling forum as a counterweight to the EMF was suggested although it is recognised that it would be preferable to move the EMF to take a less traditional approach [EM] • Demonstrations that models can simulate the recent past to provide confidence in future predictions [P9] (base-lining validation) – note that this would require a substantial team • Better estimates of the social cost of carbon including better treatment of asymmetries and the underlying values associated with these, better quantification of impacts [R7, EM] • More studies of International competitiveness, carbon leakage and spill-over [W/S, EM] • More exploration of the justice and equity implications of different mixes of adaptation versus mitigation [R10] and different approaches to adaptation • Exploration of the impact of adopting different rules (e.g. protection of the most vulnerable) and the potential application of game theory [R17]. • More regional case studies to paint a picture of the (probabilised) impacts under different scenarios.

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Update of the PAGE Model The need for more country by country case studies was identified under WP3 and the importance of bottom-up sectoral studies was identified above. The PAGE model, used by Stern, is by contrast a simple top-down aggregated model. It has proved useful for exploring some gross features of climate change economics. It is one of the few models that adopts a stochastic approach. While Stern recommends the use of bottom-up analyses, we nevertheless consider that updating the PAGE model with the latest AR4 data would be a very useful exercise. Such an exercise could also explore how co-benefits and dis-benefits, and less tangible costs and benefits can be included more rigorously in economic models and the impact of doing so. The PAGE model can be developed as a multi-criteria model. This approach allows e.g. health and mortality damages to be included explicitly in the model and discounted at an appropriate rate, rather than in combination with consumption damages. This work would complement work currently being carried out by Terry Barker and his team using the E3MG model, which is focused entirely on mitigation using economic instruments, such as carbon pricing, incentives for innovation and regulation. It is much more detailed than the PAGE model (e.g. is covers 20 world regions and 12 energy carriers) and it is designed to be estimated by formal econometric techniques on historical data. It is a component in the Tyndall’s centre’s Community Integrated Assessment System (CIAS), which has been developed over the last 8 years as an Integrated Assessment Model, capable of linking large- scale models such as E3MG and the more tractable Hadley models. E3MG and CIAS are developing stochastic solutions to allow for uncertainties in future energy prices, technological costs and climate sensitivity. This work has been underfunded in relation to the design concepts.

Valuing non-consumption impacts from climate change and mitigation One of the most difficult issues, but potentially the most important is how to value environmental and health impacts including long term bio-diversity, the preservation of ecosystems, environmental services etc [P10, 5, W/S, EM]. This requires a picture of the impacts under different scenarios/trajectories to be developed by scientists working in collaboration with impacts’ specialists in the regions. These should examine the full range of possible impacts on air quality, agriculture and health etc (see WP1) from climate change, adaptation and mitigation. Economic studies are then required to value these benefits. While a number of gaps have been identified relating to impacts studies, we believe that sufficient studies have been carried out to enable some progress to be made in this area. This was recognised as a controversial and difficult area. Water impacts and subsequent conflict (socially contingent impacts), and air quality impacts were identified as particular areas of interest. Work is beginning to gather momentum in Tyndall, NERC, QUEST and EA in this area and Defra is already talking to Tyndall.

Inclusion of induced technological change Induced technological change (ITC) has been rarely included in economic models until the recent efforts of the Innovation Modelling Comparison Project as published in AR4, although there is a longer history of it being included in energy models. This omission could cause a significant bias, not only in mitigation costs, but also in the stringency of near-term mitigation that may be justified for a given damage function or stabilisation target [8]. This is a critical gap. A particular difficulty with traditional equilibrium models is that feedback effects from reductions in costs brought about by learning can lead to unstable solutions or no solution at all. Progress has been made in including ITC in energy models, but it is notable that the 2007

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study for BERR using the MARKAL model does not include ITC, although it could be developed to do so.

Shadow Price of Carbon

Better estimates of the shadow price of carbon (SPC) associated with Government CO2 targets for 2010, 2020 and 2050 are needed for government cost-benefit analysis and planning decisions. This price is the one provided by models if the targets are to be reached, and can be calculated in a range to reflect uncertainties about energy prices and costs of technologies and co-benefits of mitigation. Since December 2007 the Social Cost of Carbon has been used as a first estimate of the SPC, but the estimates appear inconsistent with the

CO2 targets and Defra economists are investigating alternatives. The UKERC’s Energy 2050 scenarios will provide some information from UKERC modelling of the SPC associated with the 2050 CO2 target. However there is a research need for some estimates in advance of these results.

6.3 Facilitating agreement

The problem of climate change is a global one, which will require global solutions. Challenges to achieving agreement include: • The number and range of interests, the diverse impacts [5] • The need to ƒ reconcile widely divergent values [5] ƒ reach agreement on uncertain and unknown facts [5], the need to improve the evidence base to facilitate this [P1] ƒ define achievable approaches to emissions reduction and an equitable approach to target setting that people can sign up to [R3, R12] ƒ recognise and handle concerns about regional competitiveness [R19] Identification of the benefits and opportunities provided by mitigation should facilitate engagement. There has probably been a lot of work done on opportunities but this may not be in the publically available literature [P9]. Case studies (as described above) can be used to paint pictures of the benefits of action. Broadening participation, getting more countries involved and participating at the research level, is also likely to facilitate agreement [R3]. Clarification of policy/political risks may be useful. Research by political scientists in this area appears to be limited. It has been suggested that there could be scope for using game theory to give insights here, and some game theorists have published findings related to climate policy games. The assumptions used are usually rather limiting and the treatment of altruism soon turns the games chaotic, so that their outcomes become unpredictable.

6.4 Implications of targets

Areas identified as requiring research include: • How investment and planning will have to change to support scenarios [P11] • Integrating impacts and adaptation into sector planning [P9] • Developing a forward plan for traditional and non traditional sectors [P16] • Achieving food security [P9] • Legal issues arising for the Government, for example:

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ƒ If a stabilisation target is set that puts a part of the UK population at risk would there be opportunity for class action [R10]? ƒ Smooth legal transition of processes developed at Kyoto (CDM etc) will be required to avoid legal action. There needs to be backwards and forwards compatibility of changes [W/S]. ƒ Agreements reached in future must allow for ‘tightening of the belt’, leaving the way open for lowering the targets in future. No specific work packages were identified in this area.

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7 WORK PACKAGE 5: BEHAVIOURAL ASPECTS

The aim of this work package is to assess and record the available evidence on behavioural perspectives on how to avoid dangerous climate change. The United Nations Framework Convention on Climate Change (UNFCCC) commits both developed countries (Annex I Parties) and developing countries to work towards the stabilisation of greenhouse gas concentrations in the atmosphere at levels that would prevent dangerous anthropogenic interference with the climate system. This stabilisation level remains undefined in international negotiations. Part of the reason that this level has remained undefined is that different countries and cultures have different perceptions of how much climate change should be avoided and how much emissions can be reduced. Understanding these perspectives can help to facilitate agreement on a long-term goal. It is also important to understand how people reach decisions to take action at all levels (individual, government, local government [R16]), as well as in business and non-governmental organisations (NGOs) if stabilisation targets are to be achieved. Defra identified two key questions in this area: 1. For different regions and groups what is considered an acceptable risk of climate change impacts? 2. How do different regions and groups perceive emissions reductions? What reductions are acceptable? It was recognised however that thinking in this area was less developed than in other areas. The scoping study has therefore focused on identifying and summarising the kinds of issues that should be considered. The findings have been discussed under the main headings: • Behaviour of individuals and society • Communication and dialogue with individuals • Behaviour of business • National government • International perspectives, and • Wider perspectives Key research areas are then summarised.

7.1 Behaviour of individuals

In our interviews and in the literature we have found a general recognition of the importance of understanding individual attitudes towards climate change (both in the UK and internationally) and how to influence behaviours. While basic mean levels of attitude to climate change are well understood) it was generally felt that more in-depth understanding is needed.

Perceptions

People’s behaviours are driven by their perceptions and their values. Existing research on perceptions of climate change in developed nations is fairly extensive, e.g. mental models work revealing knowledge gaps and confusion of environmental issues, polling work tracks changes in perceptions over time. It does not however lead to a full understanding as yet. The research is fairly disparate, is mainly empirical and lacks a theoretical foundation . It requires a thorough integration both across disciplines and within and across countries. An

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important gap relates to perceptions of climate change and climate change mitigation strategies and policy developments within developing countries [R20]. There is a need for ongoing tracking to monitor how attitudes change over time. Tracking attitudes is important. It igives some indication whether policies are being successful in changing perceptions, it can provide an indication of what types of approach are likely to be successful and of how new policies are likely to be received. This needs to be carried out on a long term basis (e.g. not just over the next two years). There are likely to be significant differences between past perceptions and future perceptions due to key policy developments in 2007, e.g. Stern Report, IPCC report. It is important to assess how these perceptions have changed recently [R20]. It should be noted that simple tracking cannot attribute causality of changes. Tools do exist that can be used to explore not only concern about a risk issue, but also perceptions of the underlying drivers of concern (see below). We are not aware that these have been applied to climate change issues. Much of the existing research on perceptions of climate change is lacking a theoretical basis. However, there is extensive relevant theoretical evidence in other areas, for example within the domain of health behaviours [R20]. Other issues in which there has been little or no research are [R20]: • perceptions of innovative climate change policies and acceptance on a national level in different British towns and cities, or on an international level, in different countries, • perceptions of key figures, e.g. Leonardo DiCaprio, Al Gore, Arnold Schwarzenegger, and organisations, e.g. Greenpeace, IPCC, within climate change discussions – it is useful to examine how proponents of particular mitigation efforts and strategies may influence public perceptions, • public perceptions of new policy developments, both those already in existence and those

proposed in the future, e.g. offsetting carbon emissions, product labelling for CO2 emissions, personal carbon credit cards, the Climate Change Committee • public perceptions of new or existing technologies e.g. the large scale use of nuclear power. Some research is already in progress exploring the impact of significant weather events, e.g. British flooding, Hurricane Katrina, the Tsunami, on adaptation and mitigation efforts. Evidence in this area requires reviewing and integration [R20]. There is little or no research examining the impact of significant weather events on perceptions of climate change and related behaviours, e.g. are individuals affected more likely to believe climate change is happening and to conserve energy? Note also that Defra is funding related behavioural research under the Sustainable Consumption and Production (SCP) programme. The aim is to strengthen and extend understanding of: • public knowledge and emotional engagement around the issue of SCP; • the precursors to pro-environmental behaviour; • how to engage and motivate pro-environmental behaviour. The findings are intended to be applicable across policy areas (e.g. food, energy, travel, waste, water).

Values

There is little evidence with respect to what is perceived as dangerous climate change (what is subjectively seen as a tolerable or intolerable risk). The general feeling at the workshop was that there was no single answer. Rather, it depends on the severity of the consequences, to whom they occur (where in the world, in which generation) and the rate at which they occur. Table 3.1 in the Stern report illustrates the range of ‘dangers’ which climate change present. Each of these will be perceived in different ways by different people.

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People’s perceptions of the magnitude and tolerability of risk are also linked to a number of other factors, including: • the cause of the risk (e.g. society tolerates higher risk on roads than on railways), • the extent to which the risk is particularly dreaded (e.g. cancer, birth defects), • the extent to which people feel they have personal control over the risk, • the extent to which those managing the risk are trusted. Decision making driven by the risk posed by climate change (for example, whether to invest in costly or otherwise painful measures to mitigate a risk whose possible consequences lie in the distant future) is clearly a complex and uncertain area. Subjective judgements regarding the value of the future should be examined (relating to the value that should be used as a discounting rate) [R20]. One way to approach this would be to have a concerted international effort to agree a set of values associated with climate change risks. But while theoretically possible, this is likely to be impossible practically. A pragmatic alternative would be to accept that such agreement is unlikely, and that individual risk decisions will be made on the basis of (largely implicit) local value judgements [5, 3].

Behaviour

People’s perceptions and values affect attitudes; however attitude changes alone are not enough to alter behaviour. Although we understand what factors generally drive concern about risks, we do not currently understand what motivates people to respond, or not, to climate change risk and related hazards and how attitudes to different types of risk affect peoples’ choices in terms of preparing for and coping with hazards [R10]. Why, for example, do people not change their behaviour even where there are small scale, economically beneficial options open to them (e.g. fitting loft insulation) [P16]? Effective policies to change behaviour will require a raft of measures designed to inform, shift motivation, and provide the necessary infrastructure to support and provide incentives for behaviour change [R20]. Also needed is the necessary infrastructure to support and provide incentives for behaviour change in order that people develop climate friendly behavioural habits. There is a need to understand how policies will affect behaviour [R7]. For example, how will people respond to increased awareness of climate change, policy initiatives and economic pressures such as changes in fuel prices? These could be modelled to understand the projected impacts [R4].

7.2 Communication and dialogue with individuals

A precursor to people changing their behaviour voluntarily is for them to become concerned about the potential negative impacts of climate change (changing perception). However, the future impacts of climate change and the need for action may not always be clear. For example: • slow, ongoing changes may not be associated with climate change; • impacts may only be felt in the distant future, or in other countries; • there may be no direct or immediate personal benefit from action. Just presenting the risks and how bad things might not motivate people to take action (and messages that are too frightening can also lead to feelings of powerlessness). Instead there is a need to develop a vision of how the required reduction in carbon emissions can be achieved that is personal and meaningful to the individual and presents a positive vision of how they can contribute. Raising awareness of the potential impacts and how these will affect people, and what actions people can take themselves (both mitigation and adaptation) was therefore felt to be very important.

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A precursor to communication with the general public is to consider how to communicate the risks and issues surrounding climate change and different scenarios to policy makers [R15]. It is also necessary to consider what information local government might need in order to effectively communicate. Local authorities, amongst others, need to know the groups of people that are at risk from the effects of climate change (e.g. heat waves) and hence how to inform this group of the risk and the actions they could take to reduce the risks. It is important to examine social amplification processes and the impact of communications from a wide range of diverse sources. Theory and evidence on this is extensive overall but limited within the domain of climate change [R20]. It is not clear what communications methods and forms will be most effective in influencing people to adopt behaviours that will mitigate climate change. Our interviews identified uncertainty around how to inform people about both the impacts of climate change and the actions they can take to reduce their emissions. Communicating the impacts is a challenge for the reasons given above. Methodologies here should extend beyond that of simple one-way communications, to encompass more innovative public engagement approaches to dialogue with publics about science issues (the latter are particularly important for getting communities involved at a local level). Designing communications to encourage mitigating behaviours is also a challenge because of the limited number of direct or immediate personal benefits. The box below summarises the key questions raised under this topic. There is a great deal of research available in other domains that is directly relevant to these questions.

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Key questions raised include: • What information and tools can be made available in an accessible form to help people make decisions: ƒ What is the most appropriate form of information for different groups ƒ How do you translate and present the science clearly and meaningfully and should this be done differently for different audiences? ƒ Are the main messages intuitive or counter intuitive? The latter will act as a barrier to understanding ƒ Would access to a wide range of information similar to the weather forecast and tools such as MOHC models and other models be useful [R7] ƒ Can other authoritative and independent sources of information be encouraged ƒ How can levels of trust in official sources be maintained or strengthened (Note in many other fields there has been a breakdown of trust. There has been insufficient communication and overselling. • How can impacts be made tangible, in particular impacts in the distant future ƒ Should uncertainty related to impacts be communicated and if so how? ƒ Can more immediate personal benefits be identified and communicated, and where don’t these exist can these gaps be fed back to implement structural changes to create incentives/personal benefits, e.g. cheaper tax for low carbon solutions, home energy usage meters. • What effect will increased information have on: ƒ people’s awareness of the issues, ƒ people’s behaviour, and ƒ consequent emissions Is there any danger of information overload (i.e. where people receive more information, they are more likely to ignore it). • How effective have awareness raising campaigns and other information based approaches been in changing perceptions, attitudes and behaviours ƒ Has the usefulness to the end users of the information so far made available been evaluated [R7], and crucially ƒ Is systematic evaluation of campaigns planned as part of the campaign?

7.3 Behaviour of business

Successful delivery of mitigation strategies will depend on the response of companies and industries. While there is good understanding of economic drivers and economic behaviour of markets, non-economic influences and factors are less well understood. Behavioural issues include: • how organisations learn including: ƒ how businesses identify, assess and respond to climate change signals ƒ the learning process for new technologies and methods. • how businesses response to public policy including the risks of perverse behaviour (‘moral hazard’ or ‘gaming’). For example would firms rush to make carbon-emitting

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investments to avoid the possibility of more stringent regulation in the future [4]. This is considered further below. • The role played by key board-level figures and other business ‘champions’ in promoting major corporate changes towards the environment

7.4 National government and local authorities

If they are to design effective policies, policy makers need to understand how businesses and individuals are likely to respond to policies and communications. An important behavioural issue to model is the unforeseen and unintended impacts of policy initiatives, including those caused by perverse incentives. There is a need to integrate policy and behavioural changes – working the consequences all the way through to the effect on emissions. This is something that economic models do not do. Both climate policies and new and existing non-climate policies should be appraised to assess their impact on emissions.

7.5 International perspectives

Attitudes, perceptions and behaviours We have identified above that an important gap relates to perceptions of climate change and climate change mitigation strategies and policy developments within developing countries. Similarly what behaviours are likely to be similar globally and which are likely to differ significantly regionally and in what way?

Dangerous climate change, values and social choice Any consideration of what constitutes dangerous climate change raises questions about values that will differ depending on the region and context. It is necessarily a social and political judgement [3] as well as a scientific one [5]. Issues identified as requiring further discussion and exploration include: • how equity should be handled in models, how to include such factors as how people care about climate change and the significant ethical considerations connected with climate change in the discount rate and how to resolve the issues of social choice lying behind these factors [4]. Some serious consideration of this in relation to ‘contraction and convergence’ proposals might be attempted – which are likely to figure heavily in discussions at Copenhagen (see also WP4) • how to handle risk aversion, especially the conflict between risk aversion about climate change at the national scale, which is prompting early action, and risk aversion at the sector and industry level, which suggests a more cautious approach based on risks to e.g. competitiveness [R20] • how to value less tangible outcomes (health, long term biodiversity, the preservation of ecosystems, environmental services etc [P10, 5]). These issues are particularly challenging because of the many decision makers, with different value systems, that will be involved in decision making at the international level. A framework is required in which these issues can be discussed. There is a need to build a good inter-disciplinary dialogue between the people who know about the science and those who understand the social science.

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International negotiations The problem of climate change is a global one, which will require global solutions. Challenges to achieving agreement include: • The number and range of interests, the diverse impacts [5] • The need to: ƒ reconcile widely divergent values [5] ƒ reach agreement on uncertain and unknown facts [5], the need to improve the evidence base to facilitate this [P1] ƒ define achievable approaches to emissions reduction and an equitable approach to target setting that people can sign up to [R3, R12] ƒ recognise and handle concerns about regional competitiveness [R20] Identification of the benefits and opportunities provided by mitigation should facilitate engagement. There has probably been a lot of work done on opportunities but this may not be in the publically available literature [P9]. Case studies (as described above) can be used to paint pictures of the benefits of action. Broadening participation, getting more countries involved and participating at the research level, is also likely to facilitate agreement [R3]. Clarification of policy/political risks may be useful. Research by political scientists in this area appears to be limited but it is not clear if work in this area would provide practical support to negotiators.

Adaptive capacity It is important to understand what characteristics enhance vulnerability, what characteristics strengthen the adaptive capacity of some people and places, and what characteristics predispose physical, biological and human systems to irreversible changes as a result of exposure to climate and other stresses [2].

7.6 Wider perspectives

An optimistic perspective on the challenge of climate change is that if humanity collectively succeeds in meeting the challenge, then our global institutions and the general way we live together will be improved thereby. If those alive today bring about the dramatic reductions in CO2 emissions that appear to be our assignment for the next 50 years, the world will be so transformed that the options for the following 50 years will be myriad. A planetary consciousness will have become much more widespread [5]. Going beyond that, if we can stabilise the climate then could we choose to adjust it in specific ways - could our understanding/ control become such that we could actually have control over the climate? If so, this would definitely change humanity's outlook on the world, provoke ethical dilemmas and clashes in values [R9].

7.7 Research questions

This section summarises the research questions we believe it would be worthwhile addressing given the gaps and uncertainties presented in the previous sections.

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Two-Year Timescale

What behavioural and perceptions research relevant to climate change is being carried out, what would be worthwhile? While there has been limited behavioural research focused on climate change, there is a substantial body of behavioural research in other areas (e.g. behaviours towards health). Some of this research may apply to or be relevant for climate change. Therefore, existing research on behaviours and perceptions should be reviewed to determine: • what is the main research and what may be transferable to climate change related behaviours and perceptions? (This should include examination of existing programmes being carried out in Defra including the Sustainable Consumption and Production programme.) • what are the main lessons that can be transferred? • where are remaining gaps regarding our understanding perceptions and behaviours related to climate change, and would research to close those gaps be worthwhile? • who can do the research (both in the UK and internationally)?

What attitude tracking is being carried out, what would be worthwhile? A scoping and worth study for attitude tracking would determine: • What attitude studies are currently carried out (in government and elsewhere)? • What issues those studies cover and whether or not they are quantified or qualitative? • Given the above, what attitude surveys are needed (or how current ones can be improved), why and what they should measure?

Longer Timescale

Integration of behavioural and perceptions research If the scoping study suggests that there is research in other areas that can be transferred, at least in part, to climate change, the next step would be to design research projects to empirically test the applicability of this research and further develop themes.

How are attitudes to climate change changing? If the scoping study indicates that attitude tracking is feasible and worthwhile and that current studies do not meet this need, a tracking study of attitudes to climate change could be put into place (or added onto an existing attitude tracking exercise). Because an objective is to monitor how attitudes change with time there must be stability in the questions asked. This means it is important to get the questions asked ‘right first time’.

What communications methods are most effective? Research here would determine how to: • make the public aware of the potential impacts of climate change and how they will affect people; • make impacts tangible to people, in particular those impacts in the distant future; • communicate to people what actions they can take, the relative benefits of these actions and to overturn myths around actions that may be popularly perceived as beneficial that are not.

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To support this, research is needed to determine: • how effective are current communication campaigns related to climate change. This would examine: ƒ for which groups have the campaigns been most successful, ƒ do changes persist over time, and ƒ is there transference from some behaviours to others; • what lessons can be learnt from other projects • what synergies with existing programmes can be exploited; • do ‘specific’ messages transfer to other behaviours and do ‘generic’ messages impact only certain behaviours? As a general point there further communications should be designed in accordance with lessons leant and mechanisms to evaluate the results built in to the design of the initiative.

How can mitigation actions be made more tangible to individuals? Exhorting people to do something that is then found to have little benefit, or even a disbenefit can destroy trust in the climate change messages. Research is needed to understand what actions people can take themselves (both mitigation and adaptation) and which are really beneficial. This is essential information for the general public to be able to reduce their emissions. Research should be undertaken to: • identify the tangible options available to people and the actions they can take to reduce their emissions of greenhouse gasses, • evaluate the worth of these options and actions. However, experience has shown that people do not always adopt relatively straightforward and cost effective technology where it is available (such as loft insulation). An insight into the behaviour of the consumer would be gained by researching: • what are current levels of adoption of home mitigation and adaptation technology that are available to the general consumer, the focus should be on those technologies with that can have the biggest impact on emissions (e.g. insulation); • why do people buy (or not buy) such technology, which people buy what, how can uptake be improved, how can viral marketing be exploited.

How do people perceive climate change in the developing world, how is this changing? There has been significant research related to perceptions in the developed world but there has been little or nothing related to perceptions in the developing world. For the UK to influence the developing countries to grow in ways that minimise their emissions of greenhouse gases, there is a need to understand the perceptions of the developing world towards climate change, associated projects and national policies including: • what understanding of climate change and its likely impacts is there within different countries in the developing world; • how do people and significant groups, such as policy makers, perceive the actions (e.g. projects and policies) of the developed world towards climate change.

How can the behaviour of businesses be most effectively influenced? Research could be undertaken to understand: • what are the non-economic sensitivities or levers that cause companies and industries to adopt ‘greener’ ways of business (e.g. reputation, image, concern over the issues, etc);

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• what is the diffusion and update of business methods (e.g. manufacturing practices) that support the mitigation of climate change; • what is the ‘critical mass’ at which many organisations will feel obliged to ‘join the party’ regardless of their actual concern about climate change, and when is it likely to be achieved. How did existing business ‘champions’ on climate change become convinced, and how might others be brought in / persuaded?

What are the behavioural assumptions in economic models? Current economic models are important to decision-making related to the effects of climate change. Many contain (directly or indirectly) assumptions about how individuals will behave. These assumptions will have a significant affect on how realistic these models results are. However it is unclear what assumptions are being made and how robust they are. A review should be undertaken to critically review the behavioural assumptions, discount rates etc in the main economic models: • what assumptions are being made about people’s behaviour; • are these assumptions realistic and appropriate; • what are the implications of using the current assumptions; • what are better behaviour assumptions and to what degree would these improve the results from the models. A first step in such research would be to produce a set of calculations using existing models and assumptions to act as a baseline against which the effects of the changes can be assessed. There is a related field of research that investigates judgement and decision making but this has not, to our knowledge, generally assessed the types of assumptions and models that are being discussed here. Such research may be going on and an initial step would be to contact e.g. the Graduate School of Business, Columbia University (Elke Weber).

Investment and action decision model Understanding how to consider the risk posed by climate change in decision making and how to make decisions linked to it was felt to be an area of uncertainty and complexity. If, for example local governments and authorities are to make well founded decisions they will need guidance. A study should be undertaken to investigate the feasibility and scope of a decision support tool or model. Such a tool would aim to bring together the uncertain science, stakeholder and public values to use on decisions alongside the more tangible costs and benefits of the projects being considered. Such a tool or model would help consider such issues as: what is acceptable risk, what is a worthwhile amount to spend on the project being considered and when mitigation or adaptation actions are or are not worthwhile.

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8 BIBLIOGRAPHY

This bibliography contains references referred to in the appendices and additional papers or documents recommended as being particularly relevant to the workpackage.

8.1 Work Packages 1 and 2

Andreae MO, Jones CD, Cox PM, 2005: Strong present-day aerosol cooling implies a hot future. Nature 435 (7046): 1187-1190 Jun 30 2005 Boyd E, et al, 2007: The clean development mechanism: An assessment of current practice and future approaches for policy. Tyndall Working Paper No. 114. Cox PM, Betts RA, Jones CD, et al, 2000 : Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature 408 (6809): 184-187 Nov 9 2000 den Elzen M, Fuglestvedt J, Hohne N, et al, 2005: Analysing countries' contribution to climate change: scientific and policy-related choices. Environmental Science & Policy 8 (6): 614-636 den Elzen M, Meinshausen M, van Vuuren D, 2007: Multi-gas emission envelopes to meet greenhouse gas concentration targets: Costs versus certainty of limiting temperature increase. Global Environmental Change-Human And Policy Dimensions 17 (2): 260-280 May 2007 den Elzen M, van Vuuren DP, 2007: Peaking profiles for achieving long-term temperature targets with more likelihood at lower costs. Proceedings Of The National Academy Of Sciences Of The United States Of America 104 (46): 17931-17936 Nov 13 2007 Friedlingstein P, Cox P, Betts R, et al, 2006: Climate-carbon cycle feedback analysis: Results from the (CMIP)-M-4 model intercomparison. Journal Of Climate 19 (14): 3337-3353 Jul 2006 Friedlingstein P and Solomon S, 2005: Contributions of past and present human generations to committed warming caused by carbon dioxide. Proceedings Of The National Academy Of Sciences Of The United States Of America, 102 (31): 10832-10836 Hare B, Meinshausen M, 2006: How much warming are we committed to and how much can be avoided? Climatic Change 75 (1-2): 111-149 Huntingford C and Lowe J, 2007: Overshoot scenarios and climate change. Science, 316, 829 Jones CD, Cox PM, Huntingford C, 2006: Climate-carbon cycle feedbacks under stabilization: uncertainty and observational constraints. Tellus Series B-Chemical And Physical Meteorology 58 (5): 603-613 Nov 2006 Jones C, Lowe J, and Betts R: Committed ecosystem change due to climate change. Hadley Centre for Climate Prediction and Research, Contract Deliverable reference number: 08.10.06, 2007-04-10 Knutti R, Joos F, Müller SA, et al, 2005: Probabilistic climate change projections for CO2 stabilization profiles. Geophysical Research Letters, 32, L20707 Lee D et al: 2007: Response to Carter et al ‘a dual critique of the Stern review’. World Economics, vol. 8, issue 1, pages 221-228 Lowe J et al, 2006: The Role of Sea-Level Rise and the Greenland Ice Sheet in Dangerous Climate Change: Implications for the Stabilisation of the Climate. In Hans Joachim Schellnhuber et al. (eds.), Avoiding Dangerous Climate Change, 29-36 Matthews HD, Eby M, Ewen T, et al, 2007: What determines the magnitude of carbon cycle- climate feedbacks? Global Biogeochemical Cycles 21 (2): Art. No. GB2012 May 19 2007 Matthews HD, 2007: Implications of CO2 fertilization for future climate change in a coupled climate-carbon model. Global Change Biology 13 (5): 1068-1078 May 2007

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Matthews HD, Keith DW, 2007: Carbon-cycle feedbacks increase the likelihood of a warmer future. Geophysical Research Letters 34 (9): Art. No. L09702 May 4 2007 Matthews HD, 2006: Emissions targets for CO2 stabilization as modified by carbon cycle feedbacks. Tellus Series B-Chemical And Physical Meteorology 58 (5): 591-602 Nov 2006 Meehl GA, Washington WM, Collins WD, et al, 2005: How much more global warming and sea level rise? Science 307 (5716): 1769-1772 Nakashiki N, Kim D-H, Bryan FO, et al, 2006: Recovery of thermohaline circulation under CO2 stabilization and overshoot scenarios. Ocean Modelling, 15, 200-217 Rive N, Torvanger A, Berntsen T et al, 2007: To what extent can a long-term temperature target guide near-term climate change commitments. Climatic Change, 82, 373-391 Schneider SH and Mastrandrea MD, 2005: Probabilistic assessment of ‘dangerous’ climate change and emissions pathways. Proceedings of the National Academy of Sciences, 102, 15728-15735 Smith SJ, Wigley TML, 2006: Multi-gas forcing stabilization with Minicam. Energy Journal, 373-391 Sp. Iss. 3 Stott PA, Jones GS, Lowe JA, et al, 2006: Transient climate simulations with the HadGEM1 climate model: Causes of past warming and future climate change. Journal Of Climate 19 (12): 2763-2782 Tsutsui J, Yoshida Y, Kim D-H, et al, 2007: Long-term climate response to stabilized and overshoot anthropogenic forcings beyond the twenty-first century. Climate Dynamics, 28, 199- 214 van Vuuren DP, Eickhout B, Lucas PL, et al, 2006: Long-term multi-gas scenarios to stabilise radiative forcing - Exploring costs and benefits within an integrated assessment framework. Energy Journal, 201-233 Sp. Iss. 3 van Vuuren DP, Den Elzen MGJ, Lucas PL, et al, 2007: Stabilizing greenhouse gas concentrations at low levels: an assessment of reduction strategies and costs. Climatic Change 81 (2): 119-159 Mar 2007 Wigley TML, 2005: The climate change commitment. Science 307 (5716): 1766-1769 Mar 18 2005

8.2 Work Packages 3 and 4

Barker T, 2003: Representing global climate change, adaptation and mitigation, Viewpoint. Global Environmental Change 13 (2003) 1–6 Barker T, undated: The economics of avoiding dangerous climate change. Springboard Editorial for Climatic Change Issue on the Stern Review Barker T and Ekins P, 2004: The costs of Kyoto for the US economy. The Energy Journal, 25(3), pp. 53-71 Baer P and Mastrandrea M, 2006: High Stakes, Designing emissions pathways to reduce the risk of dangerous climate change. IPPR Edenhofer O, Lessman K, Kemfert C et al, 2006: Induced technological change: Exploring its implications for the economics of atmospheric stabilisation. Synthesis Report from the Innovation Modeling Comparison Project. Energy Journal (Special Issue: Endogenous Technological Change and the Economics of Atmospheric Stabilisation), pp. 1-51 Pacala S and Socolow R, 2004: Stabilization wedges: Solving the climate problem for the next 50 years with current technologies. Science, 305(5686), pp. 968 - 972. Stern N, 2008: The economics of climate change. Richard T. Ely Lecture, New Orleans.

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Weitzman ML (2007) On modeling and interpreting the economics of catastrophic climate change, http://www.economics.harvard.edu/faculty/weitzman/files/modeling.pdf Dec 5 2007. Weyant JP and Hill JN, 1999: Introduction and overview. The costs of the Kyoto Protocol: A multi-model evaluation. The Energy Journal, 20 (Special Issue), pp. vii-xliv.(EMF17) Weyant JP, de la Chesnaye FC and Blanford GJ, 2006: Overview of EMF-21: Multigas mitigation and climate policy. The Energy Journal, 27 (Special Issue #3, Multi-Greenhouse Gas Mitigation and Climate Policy), pp. 1-32

8.3 Work Packages 5

Ajzen I, 1991: The Theory of Planned Behaviour. Organizational Behaviour and Human Decision Processes, 50, 179-211 Festinger L,1954: A theory of social comparison processes. Human Relations, 7, 117-140 Fisher JD and Fisher WA, 1992. Changing AIDS-risk behaviour. Psychological Bulletin, 111, 455-474 Fishkin JS, 1995: Bringing deliberation to democracy: The British experiment. Good Society, 5, 45-49 Gollwitzer PM and Sheeran P, 2006: Implementation intentions and goal achievement: A meta-analysis of effects and processes. Advances in Experimental Social Psychology, 38, 69- 119 Kitchen PJ and Spickett-Jones G, 2003: Information processing: a critical literature review and future research directions. International Journal of Market Research, 45, 73-98 Leiserowitz AA, 2005: American Risk Perceptions: Is Climate Change Dangerous? Risk Analysis, 25, 1433-1442 Lorenzoni I, Pidgeon NF and O’Connor RE, 2005: Dangerous Climate Change: The Role for Risk Research. Risk Analysis, 25, 1387-1398 Lorenzoni I and Pidgeon NF, 2006: Public views on climate change: European and USA Perspectives. Climatic Change, 77, 73-95 Maio GR and Olson JM (Eds.): Why we evaluate: Functions of attitudes Oppenheimer M and Todorov A, 2006: Global warming: the psychology of long term risk. Climatic Change, 77: 1–6 Poortinga W and Pidgeon NF, 2004: Trust, the asymmetry principle, and the role of prior beliefs. Risk Analysis, 24(6), 1475-1486 Pidgeon NF and Rogers-Hayden T, 2007: Opening up nanotechnology dialogue with the publics: Risk communication or ‘upstream engagement’? Health, Risk and Society, 9, 191- 210 Unknown, 2008: A Framework for pro environmental behaviours. Defra Behaviours Unit. Verplanken B, 2006: Beyond frequency: Habit as mental construct. British Journal of Social Psychology, 45, 639-656 Verplanken B and Wood W, 2006: Interventions to break and create consumer habits. Journal of Public Policy and Marketing, 25, 90-103.

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