SRES Approach to Scenario Formation

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

2. 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

3. 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

4. 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.

5. 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

6. 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);

7. 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)

9. Main Scenario Driving Forces • Population - exogenous input to models 7-15 billion by 2100 • Economic Development - US$197-550 trillion by 2100 (gross world product) • Structural and Technological Change – represented by energy and land use

10. 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

12. SRES Emissions ScenariosThe 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.

18. 3000 2500 A1F1 2000 High > 1800 GtC A2 Medium High 1450-1800 GtC A1B Total Cumulative Carbon Dioxide Emissions (GtC) 1500 Medium Low 1100-1450 GtC B2 A1T 1000 Low < 1100 GtC B1 500 IS92 Range 0 1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 Cumulative Emission 1990-2100, CtC

21. AOGCM Simulations

22. Change in Sea Level Rise

23. Projections of Future Climate T ??P Spatial Scale of Uncertainty T ?P T P Uncertainty

26. Downscaling the SRES Scenarios TGCIA Activities

27. 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

28. Plans for Next IPCC Assessment

29. IPCC: 2002 to 2007 • 3 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, 2004Drafting and reviewing: 2005, 2006.

30. 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.

31. 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 1.5oC to 4.5oC range !

32. 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