1. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China) 8 th Session of AWG-KP: Technical Briefing, June 2, 2009 Science of Alternative Metrics Thomas Stocker Co-Chair IPCC WGI Physics Institute University of Bern Switzerland

2. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China)  Sep 08: Invitation by UNFCCC to IPCC to „undertake further technical assessment of common alternative metrics“;  Nov 08: IPCC Bureau selects a Scientific Steering Committee to hold an Expert Meeting: T. Stocker (Chair), O. Davidson, T. Hiraishi, R. Pichs-Madruga, S. Semenov;  Jan 09: Response by IPCC informing UNFCCC that an Expert Meeting will take place in Mar 09;  Mar 09: Expert Meeting in Oslo: 35 international experts draft and approve set of conclusions;  Apr 09: 30 th IPCC Plenary takes note of the Expert Meeting Report;  6 May 09: Full Report of the Expert Meeting sent to UNFCCC. IPCC Expert Meeting on the Science of Alternative Metrics From the UNFCCC request to the product:

3. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China) Cause-effect chain from emissions to climate change and damages (adapted from Fuglestvedt et al., 2003) Policy Relevance Uncertainty GWP GTP

4. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China) Global Warming Potential

5. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China) Global Warming Potential Global Temperature Potential

6. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China)  to UNFCCC  to the Scientific Community  to the Scoping of AR5 IPCC Expert Meeting on the Science of Alternative Metrics 3 Sets of Key Conclusions:

7. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China)  Global Warming Potential (GWP) is a well defined metric based on radiative forcing that continues to be useful in a multi-gas approach. Shortcomings have been identified; however the scientific basis has not been fully established to address these shortcomings comprehensively in any currently discussed metric;  The effectiveness of the use of a given metric depends on the primary policy goal, for example to limit the long term temperature change, limit rates of change, avoid particular impacts, and balance costs and benefits. The GWP was not designed with a particular policy goal in mind. Depending on the specific policy goal or goals, alternative metrics may be preferable;  The GWP with the time horizon of 100 years is used in the Kyoto Protocol. The numerical value of the GWP can depend markedly on the choice of time horizon. The choice of any particular time horizon involves value judgments in terms of future commitment to radiative forcing;  Timely information on potential future policy goals would facilitate research on alternative metrics. IPCC Expert Meeting on the Science of Alternative Metrics Key Conclusions to UNFCCC:

8. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China)  Uncertainties uncertainties associated with GTP, probability density functions for metrics to encompass uncertainties associated with physical processes, quantify indirect effects and interactions, mitigation costs;  New and Refined Areas or Metrics Metrics for policy targets other than  T, account for long-term, post-target, post-horizon effects, comprehensive metrics including economics;  Relationships between Policy Frameworks and Metrics impact of choice of alternative metrics on climate change outcomes and costs, extension to short-lived pollutants. IPCC Expert Meeting on the Science of Alternative Metrics Key Conclusions to the Scientific Community:

9. INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE Working Group I Co-Chairs: Thomas Stocker (Switzerland) and Qin Dahe (China)