Workshop on common metrics to calculate the CO 2 equivalence of anthropogenic greenhouse gas emissions by sources and removals by sinks Javier Hanna, UNFCCC secretariat, MDA Introduction Bonn, Germany, 3 April 2012

Outline Background The IPCC workshop on common metrics SBSTA work on common metrics AWG-KP work on common metrics UNFCCC workshop on common metrics

Background ● 2nd session (2006) of Ad Hoc Working Group on Further Commitments for Annex I Parties under the Kyoto Protocol (AWG-KP) decided that the work programme will include the analysis of possible means to achieve mitigation objectives:  Consideration of relevant methodological issues, including the global warming potentials of GHGs. ● 6th session (2008) of AWG-KP (first part):  New information on GWPs in the AR4 to calculate the CO 2 equivalence of the GHGs listed in Annex A to the Kyoto Protocol;  Findings of the AR4 relating to the shortcomings of GWPs;  There are common metrics other than GWPs that could be used to calculate the CO2 equivalence of GHGs: global temperature potentials (GTPs), mentioned in the AR4;

Background  The AR4 does not include GTP values and GTP values are not published for all GHGs included in the AR4;  Invited the IPCC to undertake further technical assessment of alternative common metrics;  Need for work to be carried out by the Subsidiary Body for Scientific and Technological Advice (SBSTA), drawing on the results of the work of the IPCC on the potential implications of applying alternative common metrics;  Further consider GWPs and alternative common metrics, as well as the implications of their application in the second commitment period of the KP.

Background ● The 6th session (2008) of AWG-KP (second part):  IPCC informed about the plans to undertake further technical assessment of alternative common metrics;  Work programme for 2009: Need for work on common metrics; At 8th session: consider issues relating to common metrics. ● SBSTA 29 (2008):  A Party on behalf of the G 77 and China requested an agenda item on common metrics be included for SBSTA 30 (2009). ● 8th session (2009) of AWG-KP:  IPCC reported on the outcome of the IPCC expert meeting on the science of alternative metrics (Oslo, Norway, March 2009); ● SBSTA 30 (2009) considered common metrics:  Consultations were inconclusive.

The IPCC workshop on common metrics Key Conclusions and Recommendations to UNFCCC: ● Global Warming Potential 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; ● Effectiveness of the use of a given metric depends on the primary policy goal (e.g. limit long term t change, limit rates of change, avoid particular impacts, and balance costs and benefits);

The IPCC workshop on common metrics Key Conclusions and Recommendations to UNFCCC: ● GWP was not designed with a particular policy goal in mind and depending on policy goal/s, alternative metrics may be preferable; ● The numerical value of GWP can depend on the choice of time horizon and this choice involves value judgments in terms of future commitment to radiative forcing; ● Timely information on potential future policy goals would facilitate research on alternative metrics.

The IPCC workshop on common metrics Recommendations to Scientific Community: Uncertainties: Characterize the uncertainties in GTPs stemming from uncertainties in climate sensitivity, climate efficacies, ocean heat uptake; Develop Probability Density Functions for metrics, and for GWPs and GTPs in particular, encompassing all sources of uncertainties; Characterize uncertainty associated with ocean heat uptake, climate sensitivity, carbon cycle response and other processes in a hierarchy of climate models; and understand and communicate the simplifications embedded in reduced complexity models; Continue to quantify magnitudes of indirect effects and interactions between different emissions, not only for long-lived GHG but also for shorter-lived pollutants; Better understand and quantify the uncertainty in mitigation costs and climate change damages.

The IPCC workshop on common metrics New and Refined Areas or Metrics: Develop metrics for policy targets other than limits to temperature change, e.g. rate of temperature change, integral of temperature change, and cost-benefit analysis approaches, or other climate variables; Develop approaches to account for long-term outcomes, e.g. consideration of post-target period for GTPs or post-horizon period for GWPs; Comprehensively assess regional differences in emissions-to- impact relationships especially for short and very-short lived pollutants; Determine the degree to which physical metrics approximate more comprehensive metrics that include economics; Consider whether existing metrics are appropriate to account for geo-engineering proposals, particularly in the context of climate protection at the regional scale.

The IPCC workshop on common metrics Relationship between Policy Frameworks and Metrics: Study implications of choice of alternative metrics for outcomes such as emissions of different gases, climate change outcomes, and costs (especially for specific countries or sectors); Investigate the potential for extending the multi-gas strategy to short-lived pollutant emissions. Recommendations to the Scoping of IPCC AR5: Assessment of metrics to be included in the IPCC AR5 process in an integrated manner with participation from all three working groups and the IPCC TFI; This process should include an assessment of, and if appropriate, numerical values for metrics proposed in the literature; The assessment should elucidate the relationship between physical metrics and more comprehensive metrics that include economics.

SBSTA work on common metrics ● SBSTA 34 (2011):  Welcomed the report of IPCC meeting on the science of alternative metrics and its conclusions and recommendations to the UNFCCC and the scientific community regarding research needs and the scoping phase of the AR5;  Secretariat should organize, subject to the availability of resources, a workshop on common metrics (first half 2012), with a focus on: i) uncertainties; ii) new and refined areas or metrics; iii) policy goals; and iv) the relationship between policy frameworks and metrics;  With purpose of providing information for further consideration under the Convention of the SBSTA 36 (2012).

SBSTA work on common metrics ● SBSTA 34 (2011) acknowledged: Alternative common metrics and shortcomings of GWPs are still being assessed by the IPCC in the context of the AR5; GWPs are a well-defined metric based on radiative forcing that continues to be useful in a multigas approach; GWPs were not designed with a particular policy goal in mind and, depending on the specific policy goals, alternative metrics may be preferable; Limitations in the use of GWPs (100-year time horizon) in evaluating the contribution to climate change of emissions of GHG with short lifetimes.

AWG-KP work on common metrics ● Decision 4/CMP.7 (Durban ):  For the second commitment period of the KP, the global warming potentials used to calculate the CO 2 equivalence of GHG in Annex A to the KP shall be those in the column entitled “Global Warming Potential for Given Time Horizon” in table 2.14 of the Errata to the contribution of WG I to the AR4, based on the effects of GHG over a 100-year time horizon, taking into account the inherent and complicated uncertainties involved in global warming potential estimates;  Alternative common metrics and the shortcomings in GWPs are still being assessed by IPCC in the context of AR5;  GWP is a well-defined metric based on radiative forcing that continues to be useful in a multi-gas approach;  GWP was not designed with a particular policy goal in mind and, depending on the specific policy goals, alternative metrics may be preferable.

● Decision 4/CMP.7 (Durban ):  Limitations of GWP (100-year time horizon) in evaluating contribution to climate change of GHG with short lifetimes;  Requests SBSTA to conduct an assessment (IPCC work) of implications of the choice of metrics for the third or subsequent KP commitment periods;  Requests the SBSTA to initiate such an assessment no later than 2015 and to present to the CMP its recommendations on the most appropriate metric and related values to be used by Parties with a view to adopt a decision;  Decision to change the metric or revise the values to calculate CO 2 equivalence of GHG shall apply only to commitment period adopted subsequent to the change or revision. AWG-KP work on common metrics

● Important step forward in the consideration of the common metrics in the SBSTA process; ● SBSTA (May 2012) will continue consideration of common metrics taking into account the workshop report; ● Space for a dialogue between the scientific community and the Parties to address the key recommendations to the UNFCCC regarding information on future policy goals and the scientific community regarding research needs:  Topic I: Uncertainties  Topic II: New and refined areas or metrics  Topic III: Policy goals  Topic IV: Relationship between policy frameworks and metrics. UNFCCC workshop on common metrics

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