SRES Approach to Scenario Formation Linda O. Mearns NCAR/ICTP GECAFS Meeting Reading, UK August 2003

Intergovernmental Panel on Climate Change (IPCC) Established by WMO and UNEP in 1988 Purpose: to assess the scientific and socio-economic information regarding climate change The IPCC has three Working Groups: Working Group I: Science of the climate system Working Group II: Impacts, vulnerability and adaptation Working Group III: Options for limiting greenhouse gases There have been three full assessments: 1990, 1995, 2001

Purpose of Scenarios WGI - provide emissions scenarios for driving Atmosphere-Ocean GCMs WGII – provision of climate change scenarios, and background scenario information (demographics, economic conditions, technology) for determining impacts of climate change on various resource systems. WGIII - need information on socio-economic settings for determining potential mitigation policy/strategies

Basis of Scenarios Extensive assessment of driving forces and emissions in the scenario literature, alternative modeling approaches, and an “open process’’ that solicited wide participation and feedback. Open process refers to use of multiple models, seeking inputs from wide community, and making results widely available for comment and review. There was an open SRES website.

Basis 2 No preference provided for any one scenario, not assigned probability of occurrence, not to be taken as policy recommendations Do not include assumption of implementation of UNFCCC or targets of the Kyoto Protocol

Process of Scenarios Development Four qualitative story lines developed Basic features and driving forces Teams modeled and quantified different storylines Resulted in the 40 emissions scenarios Six IA type models used to generate the scenarios: Asian Pacific Integrated Model (AIM); Atmospheric Stabilization Framework (ASF);

Development 2 Models (cont’d): Integrated Model to Assess the Greenhouse Effect (IMAGE); Multiregional Approach for Resource and Industry Allocation (MARIA); Model for Energy Supply Strategy Alternatives and their General Environmental Impact (MESSAGE); Mini Climate Assessment Model (MiniCAM)

Main Scenario Driving Forces Population - exogenous input to models 7-15 billion by 2100 Economic Development - US$ trillion by 2100 (gross world product) Structural and Technological Change – represented by energy and land use

Four Macro-regions OECD90 – countries belonging to OECD (Annex I countries), developed REF - countries undergoing economic reform – Eastern Europe and FSU ASIA – all developing countries in Asia ALM – all other developing countries, Latin America, Africa, Middle East

SRES Emissions Scenarios The Four Major Story Lines A1 – characterized by very rapid economic growth, global population peaking in mid-century, and then declining, and rapid introduction of new, efficient technologies. Three different subgroups in the A1 storyline are defined that present alternative changes in technology: fossil intensive (A1FI), non-fossil (A1T) and balanced across sources (A1B). A2 – characterized by heterogeneity. Self reliance and local identities are emphasized. Population increases continuously. Economic development is regionally oriented, and economic and technological growth is relatively slow, compared to other storylines. B1 – a convergent world, having the population growth of the A1 story line. Economic structures change rapidly toward a service and information economy, clean and resource-efficient technologies are introduced, with emphases on social and environmental sustainability. B2 – local solutions to economic, social and environmental sustainability is emphasized. Global population grows continuously, but at rate lower than that of A2.

Total Cumulative Carbon Dioxide Emissions (GtC) Cumulative Emission , CtC High > 1800 GtC Medium High GtC Medium Low GtC Low < 1100 GtC A1F1 A2 A1B B2 A1T B1 IS92 Range

AOGCM Simulations

Change in Sea Level Rise

Spatial Scale of Uncertainty TPTP T ?P T ??P Uncertainty Projections of Future Climate

Downscaling the SRES Scenarios TGCIA Activities

Moving from aggregate to decision-maker relevant scales SRES reported data on the level of the 4 macro-regions Many of the IA models produced results at higher resolutions CIESEN has collected high res. data – and made it available CIESEN also formally downscaled socio-economic data to nation level

Plans for Next IPCC Assessment

IPCC: 2002 to Working groups maintain same scope as in last 5 years: –WG1: Physical climate system –WG2: Impacts and Adaptation –WG3: Mitigation Fourth Assessment Report (AR4) to be completed in 2007 Planning and scoping: 2003, 2004 Drafting and reviewing: 2005, 2006.

IPCC AR4: Proposed Themes More careful approach to describing uncertainties - consistent across WGs Integrating mitigation and adaptation Identifying key vulnerabilities in regions and systems Putting climate change in the context of sustainable development Adopting a consistent regional approach across WGs.

IPCC WG1: Likely issues (1) Avoiding the “tyranny of the global mean” – greater regional focus Updating climate change scenarios for impact studies (particularly for vulnerable regions: polar, monsoon, coral reefs,… ) New focus on Climate – Water issues Climate Sensitivity – how do we reduce the 1.5 o C to 4.5 o C range !

IPCC WG1: Likely issues(2) Emission scenarios –rely mainly on existing scenarios, but… –black carbon emissions –climate change feedbacks on natural emissions –harmonizing SRES scenarios with the 1990 – 2005 period Direct influence of aerosols on the hydrological cycle