WORKING PAPER Center for International Forestry Research (CIFOR) CIFOR advances human wellbeing, environmental conservation, and equity by conducting research to inform policies and practices that a ect forests in developing countries. CIFOR is one of 15 centres within the Consultative Group on International Agricultural Research (CGIAR). CIFOR’s headquarters are in Bogor, Indonesia. It also has o ces in Asia, Africa and South America. CIFOR works in over 30 countries worldwide and has links with researchers in 50 international, regional and national organisations. To request a copy of this publication, please contact [email protected] www.cifor.cgiar.org Climate Scenarios: What we need to know and how to generate them Heru Santoso Monica Idinoba Pablo Imbach CIFOR Working Paper No. 45 Climate Scenarios: What we need to know and how to generate them Heru Santoso Monica Idinoba Pablo Imbach December 2008 2 CLIMATE SCENARIOS: WHAT WE NEED TO KNOW AND HOW TO GENERATE THEM Contact Heru Santoso Center for International Forestry Research (CIFOR) P.O. Box 0113 BOCBD Bogor 16000 Indonesia Tel: +62 251 8622 622 Fax: +62 251 8622 100 Email: [email protected] Cover photo by Meria Azis Acknowledgements The authors thank peers who reviewed earlier drafts of this report: Bruno Locatelli and Armi Susandi. Disclaimers The views expressed in this publication are those of the author(s) and not necessarily those of CIFOR. This document has been produced with the financial assistance of the European Union (EuropeAid/ENV/2004- 81719). The contents of this document can under no circumstances be regarded as reflecting the position of the European Union. WORKING PAPER NO. 45 3 Table of contents Summary 4 1 Introduction 5 2 Do we need climate scenarios for adaptation? 6 3 What climate data do we need? 8 4 What are the different types of climate scenarios? 9 5 Which emission scenarios should be used? 11 6 Which GCM to choose? 12 7 How to modify the spatial resolution of climate data? 14 8 How to modify the temporal resolution of climate data? 16 9 How to deal with uncertainties? 17 10 Can we assess extreme events? 19 11 Where to find additional information? 20 12 Conclusions 22 References 23 Glossary 25 4 CLIMATE SCENARIOS: WHAT WE NEED TO KNOW AND HOW TO GENERATE THEM Summary Climate change profoundly affects the natural and social environment. Decision-makers and resource managers require information regarding future changes in climate average and variability to better anticipate potential impacts of climate change. This book provides some overviews on the roles of climate scenarios in adaptation planning and what should be considered in using and generating climate scenarios, in a frequently ask questions style. Specifically, this book tries to answer questions commonly addressed by non-climatologists when they want to address climate scenario in adaptation plans. It covers topics on the need of climate scenarios for adaptation, types of climate data or information we need, different types of climate scenarios, emission scenarios, choosing general circulation model (GCM), how to modify the spatial and temporal resolution of climate data, how to deal with uncertainties, and the progress of the climate models in assessing extreme events. The book also provides additional information regarding tools and sources of data in relation to climate scenario. WORKING PAPER NO. 45 5 1. Introduction limate change profoundly affects the natural prediction or forecast (IPCC 2007a)1. Climate science and social environment. For example, changes in this context has contributed significantly to the Cin seasonal to interannual climate strongly affect understanding of current changes and the projection agricultural production, the quantity and quality of of long-term future changes in climate that result from water resources, and resources coming from land and both natural and human influences (IPCC 2007b). marine ecosystems. IPCC (2007b) indicates several Climate scenarios, which often serve as input to key impacts on different sectors that are correlated impact models, are commonly constructed through with climate change such as freshwater resources and projections. These projections are the response of the their management; ecosystems; food, fibre and forest climate system to emission scenarios of greenhouse products; coastal systems and low lying areas; industry, gases and aerosols. There are variety of models to settlement and society; and health. simulate future climate (Cotton and Pielke 1995) that Decision-makers and resource managers require contain embedded assumptions. Long-term projections information regarding future changes in climate average beyond the 2050s heavily depend on these models and and variability to better anticipate potential impacts simulations, because the compositions of anthropogenic of climate change. However, future climate patterns elements that affect the climate (eg greenhouse gas are difficult to predict (Goodess 2000). In particular, concentration, land cover condition, demographic the future radiative forcing from greenhouse gases is composition and distribution, socio-economic difficult to quantify because the emissions of these conditions etc) are different from the current and near gases depend on many assumptions and uncertain future compositions. factors such as population growth, the use of carbon This book discusses some roles of climate fuel as an energy source, technological development, scenarios in adaptation planning, and what should be economic development, policy and attitudes towards considered in using and generating climate scenarios, environment, etc (see Nakićenović et al. 2000; IPCC- in a ‘frequently asked questions’ style. Specifically, this TGICA 2007). For this reason, climate scenarios book tries to answer questions commonly addressed by have been developed to investigate the potential non-climatologists, such as adaptation practitioners, consequences of anthropogenic climate change. policymakers and resource managers, when they want Therefore, a climate scenario differs from a climate to address climate scenario in adaptation plans. 1 Definitions from IPCC (2007a): A climate prediction or climate forecast is the result of an attempt to produce an estimate of the actual evolution of the climate in the future, eg at seasonal, interannual or long-term time scales. A climate scenario is a plausible and often simplified representation of future climate, based on an internally consistent set of climatological relationships and assumptions of radiative forcing, typically constructed for explicit use as input to climate change impact models. 6 CLIMATE SCENARIOS: WHAT WE NEED TO KNOW AND HOW TO GENERATE THEM 2. Do we need climate scenarios for adaptation? Dessai et al. (2005) discussed the role of climate based on this assumption may be inadequate or scenarios in three different types of adaptation irrelevant in the future if characteristics of climate in approaches. They are the IPCC approach, human the future are substantially different from those under development approach, and risk approach. This section the present conditions. This approach is, therefore, less summarises each approach in the context of whether appropriate if used for designing a long-term adaptation the climate scenario is needed or not. plan. IPCC approach Risk approach IPCC approach follows a traditional approach of Risk assessment is part of a risk management process to impact assessment in which using climate scenario is an reduce risk to human health and to ecosystems. Central important step towards adaptation planning (Dessai et to risk assessment is the management of uncertainties, al. 2005). In the case of adaptation programme in the which allows the risk of a potentially disastrous event multinational Mekong river basin in South East Asia2, to be determined and reduced (Dessai et al. 2005). for example, a highly quantitative impact assessment Climate scenarios are used as a tool to assess the through modelling was employed to estimate the relationship between climate change and the event, possible implications of climate and land cover and to identify the impact thresholds to be analysed changes for water resources and the dependent sectors for risk. In this approach climate scenarios are not the (agriculture, freshwater fisheries, aquatic habitat), and centre of the assessment, but they can support threshold for the livelihood of the communities. High quality identification, uncertainty quantification and planning climate scenario information plays a central role in action to reduce risk. determining who or what is vulnerable and how to enhance the adaptive capacity for the vulnerable sectors Adaptation Policy Framework and communities. The Adaptation Policy Framework (APF) considers Human development approach adaptation as a continuum from current to future in which current vulnerability and future climate change Human development approaches argue that steps risk are characterised as a continuous process (Burton et to improve present levels and types of adaptation to al. 2002). It is addressed here, because this framework reduce present vulnerability are essential to overcoming appears to link the human development approach and impacts of climate change in the future (Dessai et al. the risk approach. In this framework, climate scenarios 2005). This approach considers that vulnerability is are useful in characterising future climate risks and for driven by both climatic and non-climatic stresses. The evaluating the performance