Climate Change 2001: Synthesis Report Synthesis Report An Assessment of the Intergovernmental Panel on Climate Change This underlying report, approved paragraph by paragraph at IPCC Plenary XVIII (Wembley, United Kingdom, 24-29 September 2001), represents the formally agreed statement of the IPCC concerning key findings and uncertainties contained in the Working Group contributions to the Third Assessment Report. Based on a draft prepared by: Core Writing Team Robert T. Watson, Daniel L. Albritton, Terry Barker, Igor A. Bashmakov, Osvaldo Canziani, Renate Christ, Ulrich Cubasch, Ogunlade Davidson, Habiba Gitay, David Griggs, Kirsten Halsnaes, John Houghton, Joanna House, Zbigniew Kundzewicz, Murari Lal, Neil Leary, Christopher Magadza, James J. McCarthy, John F.B. Mitchell, Jose Roberto Moreira, Mohan Munasinghe, Ian Noble, Rajendra Pachauri, Barrie Pittock, Michael Prather, Richard G. Richels, John B. Robinson, Jayant Sathaye, Stephen Schneider, Robert Scholes, Thomas Stocker, Narasimhan Sundararaman, Rob Swart, Tomihiro Taniguchi, and D. Zhou Extended Team Q.K. Ahmad, Oleg Anisimov, Nigel Arnell, Fons Baede, Tariq Banuri, Leonard Bernstein, Daniel H. Bouille, Timothy Carter, Catrinus J. Jepma, Liu Chunzhen, John Church, Stewart Cohen, Paul Desanker, William Easterling, Chris Folland, Filippo Giorgi, Jonathan Gregory, Joanna Haigh, Hideo Harasawa, Bruce Hewitson, Jean-Charles Hourcade, Mike Hulme, Tom Karl, Pekka E. Kauppi, Rik Leemans, Anil Markandya, Luis Jose Mata, Bryant McAvaney, Anthony McMichael, Linda Mearns, Jerry Meehl, Gylvan Meira-Filho, Evan Mills, William R. Moomaw, Berrien Moore, Tsuneyuki Morita, M.J. Mwandosya, Leonard Nurse, Martin Parry, Joyce Penner, Colin Prentice, Venkatachalam Ramaswamy, Sarah Raper, Jim Salinger, Michael Scott, Roger A. Sedjo, Priyaradshi R. Shukla, Barry Smit, Joel Smith, Leena Srivastava, Ron Stouffer, Kanako Tanaka, Ferenc L. Toth, Kevin Trenberth, Alla Tsyban, John P. Weyant, Tom Wilbanks, Francis Zwiers, and many IPCC authors Review Editors Susan Barrell, Rick Bradley, Eduardo Calvo, Ian Carruthers, Oyvind Christophersen, Yuri Izrael, Eberhard Jochem, Fortunat Joos, Martin Manning, Bert Metz, Alionne Ndiaye, Buruhani Nyenzi, Ramon Pichs-Madruga, Richard Odingo, Michel Petit, Jan Pretel, Armando Ramirez, Jose Romero, John Stone, R.T.M. Sutamihardja, David Warrilow, Ding Yihui, and John Zillman Question 1 What can scientific, technical, and socio-economic analyses contribute to Q1 the determination of what constitutes dangerous anthropogenic interference with the climate system as referred to in Article 2 of the Framework Convention on Climate Change? Framework Convention on Climate Change, Article 2 “The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.” Climate Change 2001 Synthesis Report 1.1 Natural, technical, and social sciences can provide essential information and WGII TAR Section 2.7 & evidence needed for decisions on what constitutes “dangerous anthropogenic WGIII TAR Chapter 10 interference” with the climate system. At the same time, such decisions are value judgments determined through socio-political processes, taking into account considerations such as development, equity, and sustainability, as well as uncertainties and risk. Scientific evidence helps to reduce uncertainty and increase knowledge, and can serve as an input for considering precautionary measures.1 Decisions are based on risk assessment, and lead to risk management choices by decision makers, about actions and policies.2 1.2 The basis for determining what constitutes “dangerous anthropogenic WGII TAR Chapter 18 & interference” will vary among regions, depending both on the local nature WGIII TAR Chapter 10 and consequences of climate change impacts, and also on the adaptive capacity available to cope with climate change. It also depends upon mitigative capacity, since the magnitude and the rate of change are both important. The consequent types of adaptation responses that will be selected depend on the effectiveness of various adaptation or mitigation responses in reducing vulnerabilities and improving the sustainability of life-support systems. There is no universally applicable best set of policies; rather, it is important to consider both the robustness of different policy measures against a range of possible future worlds, and the degree to which such climate- specific policies can be integrated with broader sustainable development policies. 1.3 The Third Assessment Report (TAR) provides an assessment of new scientific WGI TAR, WGII TAR, & information and evidence as an input for policy makers in their determination WGIII TAR of what constitutes “dangerous anthropogenic interference with the climate system” with regard to: (1) the magnitudes and rates of changes in the climate system, (2) the ecological and socio-economic impacts of climate change, and (3) the potential for achieving a broad range of levels of concentrations through mitigation and information about how adaptation can reduce vulnerability. 1.4 With regard to the magnitudes and rates of changes in the climate system, WGI TAR the TAR provides scenario-based projections of future concentrations of greenhouse gases in the atmosphere, global and regional patterns of changes and rates of change in temperature, precipitation, and sea level, and changes in extreme climate events. It also examines possibilities for abrupt and irreversible changes in ocean circulation and the major ice sheets. 1.5 The TAR reviews the biophysical and socio-economic impacts of climate WGII TAR Chapter 19 change. The TAR articulates five reasons for concern, regarding: • Risks to unique and threatened systems • Risks associated with extreme weather events • The distribution of impacts • Aggregate impacts • Risks of large-scale, high-impact events. Of great significance here is an assessment of the likelihood of the critical thresholds at which natural and human systems exhibit large-scale, abrupt, or irreversible changes in their response to a changing climate. Since no single indicator (e.g., a monetary unit) captures 1 Conditions that justify the adoption of precautionary measures are described in Article 3.3 of the United Nations Framework Convention on Climate Change (UNFCCC). 2 The risk associated with an event is most simply defined as the probability of that event, multiplied by the magnitude of its consequence. Various decision frameworks can facilitate climate risk assessment and management. These include, among others, cost-benefit analysis, cost-effectiveness analysis, multi-attribute analysis, and tolerable windows. Such techniques help to differentiate the risk levels associated with alternative futures, but in all cases the analyses are marked by considerable uncertainties. 38 IPCC Third Assessment Report Synthesis Report Question 1 the range of relevant risks presented by climate change, a variety of analytical approaches and criteria are required to assess impacts and facilitate decisions about risk management. 1.6 With regard to strategies for addressing climate change, the TAR provides WGII TAR Chapter 18 & an assessment of the potential for achieving different levels of concentrations WGIII TAR Chapter 2 through mitigation and information about how adaptation can reduce vulnerability. The causality works in both directions. Different stabilization levels result from different emission scenarios, which are connected to underlying development paths. In turn, these development paths strongly affect adaptive capacity in any region. In this way adaptation and mitigation strategies are dynamically connected with changes in the climate system and the prospects for ecosystem adaptation, food production, and sustainable economic development. 1.7 An integrated view of climate change considers the dynamics of the complete cycle of WGII TAR Chapters 1 & 19, interlinked causes and effects across all sectors concerned. Figure 1-1 shows the cycle, WGIII TAR Chapter 1, & SRES from the underlying driving forces of population, economy, technology, and governance, through greenhouse gas and other emissions, changes in the physical climate system, biophysical and human impacts, to adaptation and mitigation, and back to the driving forces. The figure presents a schematic view of an ideal “integrated assessment” framework, in which all the parts of the climate change problem interact mutually. Changes in one part of the cycle influence other components in a dynamic manner, through multiple paths. The TAR assesses new policy-relevant information and evidence with regard to all quadrants of Figure 1-1. In particular, a new contribution has been to fill in the bottom righthand quadrant of the figure by exploring alternative development paths and their relationship to greenhouse gas emissions, and by undertaking preliminary work on the linkage between adaptation, mitigation, and development paths. However, the TAR does not achieve a fully integrated assessment of climate change, because of the incomplete state of knowledge. 1.8 Climate