Status of research SB-20 21 June 2004

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

2. Overview • Introduction to the MATCH processNiklas Höhne / Xiaosu Dai • Introduction of first joint paperMichel 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 23rd session (Nov 2005). Modelling and assessment of contributions to climate change

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

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

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 • Background • Organization • Papers • Expert meetings • File exchange • Discussion forum Modelling and assessment of contributions to climate change

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 responses—CO2 emissions due to fossil fuels, CO2 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 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 Modelling and assessment of contributions to climate change

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 Source: UNFCCC Modelling and assessment of contributions to climate change

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 Source: Ecofys-ACCC Modelling and assessment of contributions to climate change

22. 1. Indicators *: 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 Modelling and assessment of contributions to climate change

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

24. 1. Indicators • 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. Modelling and assessment of contributions to climate change

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 • 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 Modelling and assessment of contributions to climate change

27. End-date • 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 Modelling and assessment of contributions to climate change

28. Evaluation-date • 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 Modelling and assessment of contributions to climate change

29. 3.Attribution methods • 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. Modelling and assessment of contributions to climate change

30. 3.Attribution methods • 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. Modelling and assessment of contributions to climate change

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

32. 3.Attribution methods • 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 Source: CSIRO-SCM Modelling and assessment of contributions to climate change

33. 4.Greenhouse gas mixture Which gases are attributed to the regions? • Fossil CO2 • All anthropogenic CO2 • CO2, CH4, N2O • Kyoto basket (CO2, CH4, N2O, HFCs, PFCs, SF6) • Kyoto basket + more O3 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 CO2 emissions only to total anthropogenic CO2 emissions, ii) Inclusion of CH4 and N2O. • The effect is less pronounced on longer time scales (except for the shift from fossil CO2 to total CO2). Source: CICERO-SCM Modelling and assessment of contributions to climate change

35. Scientific uncertainties • Choice of the dataset on historical emissions • 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 CO2 emissions: small differences in relative attribution • CO2 emissions from land-use changes: differences in estimates leading to large differences. Data sets need to be compared and improved. • CH4 and N2O: Only one dataset is available (EDGAR) Source: RIVM-ACCC Modelling and assessment of contributions to climate change

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 Source: CICERO-SCM Modelling and assessment of contributions to climate change

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