1. Status of research SB-20 21 June 2004 Xiaosu Dai, Michel den Elzen, Niklas Höhne

2. Overview 1.Introduction to the MATCH process Niklas Höhne / Xiaosu Dai 2.Introduction of first joint paper Michel den Elzen / Niklas Höhne Modelling and assessment of contributions to climate change

3. SBSTA 17 (Oct 2002) Work should be continued by the scientific community, in particular to improve the robustness of the preliminary results and to explore the uncertainty and sensitivity Be of a standard consistent with the practices of peer-reviewed published science. The process should be inclusive, open and transparent. Capacity building: strongly encouraged Parties and institutions to facilitate capacity-building in developing countries, including by hosting scientists from developing countries Invited the scientific community, including IGBP, WCRP, IHDP and IPCC to provide information on how they could contribute Encouraged scientists to undertake further work, to make the results of their work publicly available and to report progress at SBSTA 20, June 2004 (side event). SBSTA decided to review the progress at its 23 rd session (Nov 2005). Modelling and assessment of contributions to climate change

4. MATCH process Modelling and assessment of contributions to climate change UNFCCC process Two expert meetings Coordinated modelling exercise ACCC Ad-hoc group Initiated by Brazil and UK Two expert meetings so far

5. MATCH process Objective: Assess methods for calculating the contribution of different emission sources (e.g. regional, national or sectoral) to climate change and its impacts, taking into account uncertainties, and the sensitivity of the calculations to the use of different methods, models and methodological choices. Outputs: Provide clear guidance on the implications of the use of the different scientific methods, models, and methodological choices Where scientific arguments allow, recommend one method/model/choice or several possible methods/models/choices for each step of the calculation of contributions to climate change, taking into account scientific robustness, practicality and data availability Organization of expert meetings, workshops and a coordinated modelling exercise Prepare papers to be published in peer reviewed scientific journals Modelling and assessment of contributions to climate change

6. MATCH process Scientific Coordination Committee Modelling and assessment of contributions to climate change Xiaosu DaiNational Climate Center, China Michel den ElzenRIVM, Netherlands Jan FuglestvedtCICERO, Center for International Climate and Environmental Research - Oslo, Norway Jason LoweMet Office, Hadley Centre for Climate Prediction and Research, UK Joyce PennerUniversity of Michigan, USA Michael Prather (Chair)University of California at Irvine, USA Cathy TrudingerCSIRO Atmospheric Research, Australia Murari LalIIT, India José Domingos Gonzalez Miguez Interministerial Committee on Global Climate Change, Brazil Niklas Höhne (Secretary)ECOFYS, Germany

7. MATCH process Developing country participation: Fund for travel costs of developing country experts sponsored by governments of Germany, Norway, UK (currently funds for further 15 developing country expert trips) Support unit: Ecofys under contract to UK Defra Information: http://www.match-info.net Modelling and assessment of contributions to climate change

8. MATCH-info.net Modelling and assessment of contributions to climate change Background Organization Papers Expert meetings File exchange Discussion forum

9. Participation at last meeting Modelling and assessment of contributions to climate change

10. Individual scientific papers Pinguelli & Kahn (2001): The present, past, and future contributions to global warming of CO2 emissions from fuels, Climatic Change den Elzen and Schaeffer (2002): Responsibility for past and future global warming: Uncertainties in attributing anthropogenic climate change, Climatic Change Trudinger & Enting (2004): Comparison of formalisms for attributing responsibility for climate change: Non-linearities in the Brazilian Proposal approach, Climatic Change Andronova and Schlesinger (2004): Importance of sulfate aerosol in evaluating the relative contributions of regional emissions to the historical global temperature change attribution methods, Mitigation and Adaptation Strategies for Global Change den Elzen, Schaeffer and Lucas (2004): Differentiating future commitments on the basis of countries' relative historical responsibility for climate change: uncertainties in the 'Brazilian Proposal' in the context of a policy implementation, Climatic Change Pinguelli, Kahn, Muylaert and Pires de Campos (2004): Comments on the Brazilian Proposal and contributions to global temperature increase with different climate responsesCO 2 emissions due to fossil fuels, CO 2 emissions due to land use change, Energy Policy Höhne and Harnisch (2004): Calculating historical contributions to climate change – discussing the Brazilian Proposal, Climatic Change Modelling and assessment of contributions to climate change

11. Anticipated papers Paper #1 Analysing countries contribution to climate change: Scientific choices and methodological issues: status of the work and first results Paper #2 Demonstration of credible alternative scientific choices and their effect on the emissions, concentration and climate change Paper #3 Formal assessment of uncertainties and clarify parameter space Paper #4 Additional attribution calculations discussed in paper #1 by including the outputs from paper #2 and paper #3 Modelling and assessment of contributions to climate change

12. Schedule Meeting September 2003: Formation of the ad-hoc group MATCH Agreement on terms of reference, scientific coordination committee, research questions Modelling and assessment of contributions to climate change Meeting May 2004: Discussion of draft paper #1 Discussion of development of further papers June 2004: SB 20 side event Meeting December 2004 (tentatively 2/3 December in Brazil): Discussion of draft paper #2 Discussion of development of further papers Meeting May 2005: Discussion of draft paper #3 Meeting September 2005: Discussion of draft paper #4 SB 23 November 2005: Presentation of results

13. Remarks Challenges New research Resource requirements for contributing experts Links to other organizations and programmes Ambitious schedule Strong points of MATCH Participation of leading experts on the topic Joint research effort Results are peer-reviewed publications Modelling and assessment of contributions to climate change

14. 2. First joint paper Analysing countries contribution to climate change: Scientific choices and methodological issues Modelling and assessment of contributions to climate change

15. Main objective of paper #1 to summarise the studies and results so far (i.e. the contributions to the UNFCCC initiated process) to present new attribution calculations with non-linear carbon cycle and climate models using non-linear attribution methodologies and updated historical emissions datasets to investigate the effect of a range of scientific, methodological and policy-related choices on the attribution, but not the full range by all uncertainties. Modelling and assessment of contributions to climate change

16. Policy choices Policy choices refer: to parameters of which the values can not be based on objective scientific arguments alone. For example, 100 year time horizon of GWPs. The choices have to be made largely within the policy context. Policy choices analysed here: –Indicator –Timeframes –Emission scenarios –Mixture of Greenhouse gases –Attribution method Modelling and assessment of contributions to climate change

17. Scientific uncertainties Choice of the dataset on historical emissions Choice of the representation of the climate system (different models) Modelling and assessment of contributions to climate change

18. Models used Modelling and assessment of contributions to climate change

19. Model show similar outcomes Modelling and assessment of contributions to climate change Source: UNFCCC

20. Policy choices 1. Indicator 2. Timeframes 3. Attribution method 4. Mixture of greenhouse gases Modelling and assessment of contributions to climate change

21. 1. Indicators Modelling and assessment of contributions to climate change Source: Ecofys-ACCC

22. 1. Indicators Modelling and assessment of contributions to climate change *: Also discounting most recent emissions + : Can be made forward looking, when evaluating at a date after attributed emissions end. In such case also a time horizon is required

23. 1. Indicators Modelling and assessment of contributions to climate change Relative contributions using different indicators Preliminary

24. 1. Indicators Modelling and assessment of contributions to climate change Conclusions Two main factors influence results Whether a source emitted early versus late The share of emissions of short-lived / long-lived gases. Choosing the right indicator is ultimately a policy choice that also depends on the purpose of use of the results. Temperate increase: use evaluation date after the attribution end date Backward discounting and forward looking: weighted concentrations or integrated temperature Not backward discounting: GWP-weighted cumulative emissions could be an option, which is simple and approximately represents the integrated impact on temperature.

25. 2. Timeframe Start date emissions 1890, 1950 and 1990 End date emissions 1990, 2000, 2050 and 2100 Evaluation date of attribution 2000, 2050, 2100, 2500 Modelling and assessment of contributions to climate change

26. Start-date Modelling and assessment of contributions to climate change Choosing a shorter time horizon (e.g. 1950 or 1990 instead of 1890) reduces the contributions of OECD90 countries ('early emitters') to temperature increase. Source: RIVM-ACCC

27. End-date Modelling and assessment of contributions to climate change A late end-date increases non-Annex-I contributions, because it gives more weight to their larger future emissions. Impact of emissions scenarios (error bars) can be large Source: RIVM-ACCC

28. Evaluation-date Modelling and assessment of contributions to climate change A later evaluation-date raises OECD contributions due to: (1) their large share in historical CO2 emissions (long residence time) (2) and their small share of methane emissions (short residence time) Source: RIVM-ACCC

29. 3. Attribution methods Modelling and assessment of contributions to climate change Normalised marginal method - Attributes responsibility using total sensitivities determined "at the margin". Residual (all-but-one) method - Attributes responsibility by leaving out the emissions of each region in turn. Time-sliced - determines the effect of emissions from each time as if there were no subsequent emissions.

30. 3. Attribution methods Modelling and assessment of contributions to climate change The Residual method, although simple to implement and explain, can be rejected on scientific grounds (not additive). The Normalised marginal and Time- sliced methods are harder to implement and explain. These methods differ in how they treat early vs. late emissions.

31. 3. Attribution methods The differences between methods are fairly small compared to the effects of many of the other choices already considered. Modelling and assessment of contributions to climate change Source: CSIRO-SCM

32. 3. Attribution methods Modelling and assessment of contributions to climate change Source: CSIRO-SCM Differences between methods are greater for later evaluation date (2100) In general, the results of the different methods vary most for regions with emissions that differ most from the average in terms of early versus late emissions, i.e. India and EU. Source: CSIRO-SCM

33. 4. Greenhouse gas mixture Which gases are attributed to the regions? 1.Fossil CO 2 2.All anthropogenic CO 2 3.CO 2, CH 4, N 2 O 4.Kyoto basket (CO 2, CH 4, N 2 O, HFCs, PFCs, SF 6 ) 5.Kyoto basket + more O 3 precursors (NOx, CO and VOC) Modelling and assessment of contributions to climate change

34. 4. Greenhouse gas mixture Two main effects i) Going from fossil fuel CO 2 emissions only to total anthropogenic CO 2 emissions, ii) Inclusion of CH 4 and N 2 O. The effect is less pronounced on longer time scales (except for the shift from fossil CO 2 to total CO 2 ). Modelling and assessment of contributions to climate change Source: CICERO-SCM

35. Scientific uncertainties 1.Choice of the dataset on historical emissions 2.Choice of the representation of the climate system: carbon cycle and climate model and feedbacks Modelling and assessment of contributions to climate change

36. 1. Historical datasets Fossil CO 2 emissions: small differences in relative attribution CO 2 emissions from land-use changes: differences in estimates leading to large differences. Data sets need to be compared and improved. CH 4 and N 2 O: Only one dataset is available (EDGAR) Modelling and assessment of contributions to climate change Source: RIVM-ACCC

37. 2. Other scientific uncertainties The influence of other climate model parameters (e.g. IRFs), based on simulation experiments with nine GCMs and climate models is limited Including additional non-linearities in calculations of methane-concentrations (IPCC-TAR atmospheric chemistry model ) has a negligible effect on the relative contributions... Modelling and assessment of contributions to climate change

38. Overall conclusions First summary of the work undertaken to date. Not a full assessment of the uncertainty range, but an evaluation of the influence of different policy-related and scientific choices. The influence of scientific choices is notable. Therefore research is ongoing (see papers #2 and #3) However, the current work suggests, that the impact of policy choices, such as time horizon of emissions, climate change indicator and greenhouse-gas mix is larger than the impact of scientific uncertainties Impact of uncertainties on the relative contributions is smaller than impact of uncertainties on the absolute changes in temperature. Research needs: Historical emission datasets Modelling and assessment of contributions to climate change

39. Backup slides

40. Policy choices Modelling and assessment of contributions to climate change

41. Models are calibrated Modelling and assessment of contributions to climate change

43. Table 3

44. Contribution to radiative forcing Modelling and assessment of contributions to climate change

45. Aerosol forcing Inclusion of SO2 emissions reduces the contributions from ASIA and REF, but the effect disappear when there is a gap between attribution end date and evaluation date. Again effect is less less pronounced on longer time scales Modelling and assessment of contributions to climate change Source: CICERO-SCM

46. Policy choices vs. scientific choices Policy choices (start-date, indicators) are more important than scientific uncertainties (attribution method, climate model) Modelling and assessment of contributions to climate change Source: RIVM-ACCC