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Uncertainties in implementation of common metrics Jolene Cook, 3 April 2012, Bonn

Uncertainties in implementation of common metrics Jolene Cook, 3 April 2012, Bonn

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Uncertainties in implementation of common metrics Jolene Cook, 3 April 2012, Bonn

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  1. Uncertainties in implementation of common metrics Jolene Cook, 3 April 2012, Bonn With thanks to: Chris Huntingford (CEH), Laila Gohar (Met Office Hadley Centre), Nick Howarth (Oxford Univ.), Myles Allen (Oxford Univ.), Alex Lorenz (Oxford Univ.), Keith Shine (Reading Univ.), Bill Collins (Met Office Hadley Centre), Jason Lowe (Met Office Hadley Centre), David Lee (Tau Scientific)

  2. Uncertainties in current knowledge and use of metrics • Physical • e.g. climate sensitivity, radiative impact • Structural • e.g. impact of different lifetimes, choice of time horizon, relationship with end impact • Economic • e.g. choice of discount rate, potential for perverse incentives • Political • e.g. winners and losers, ease of communication, stability UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  3. Value choices affect metrics • Policy goals, e.g. 2°C, emission trading, reporting and monitoring • What’s included in the basket of gases • Revisions due to new evidence, e.g. SAR to AR4. • Choice of metric, e.g. GWP, GTP or other? • Choice of time horizon UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  4. Value choices affect metrics • Policy goals, e.g. 2°C, emission trading • What’s included in the basket of gases • Revisions due to new evidence, e.g. SAR to AR4 • Choice of metric, e.g. GWP, GTP or other? • Choice of time horizon UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  5. Value choices affect metrics • Policy goals, e.g. 2°C, emission trading • What’s included in the basket of gases • Revisions due to new evidence, e.g. SAR to AR4 • Choice of metric, e.g. GWP, GTP or other? • Choice of time horizon UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  6. Impact of new evidence:updating GWP values Source: IPCC 2007; UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  7. 60 High 26.4%  26.2%  N2O 50 CH4 CO2 40 30 20 10 0 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 AR4 SAR Impact of new evidence Global total CO2e emissions per year (GWP100) UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  8. 12 High F gases 160%  155%  Smaller increase N2O 10 CH4 CO2 No change 8 8.6%  8.6%  No significant effect 8.2%  8.5%  6 4 Smaller decrease 7.9%  6.5%  2 0 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 Impact of new evidence CO2e emissions per year (GWP100) SAR SAR SAR SAR AR4 AR4 AR4 AR4 China USA EU-27 Brazil UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  9. Value choices affect metrics • Policy goals, e.g. 2°C, emission trading • What’s included in the basket of gases • Revisions due to new evidence, e.g. SAR to AR4 • Choice of metric, e.g. GWP, GTP or other? • Choice of time horizon UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  10. Impact of choice of metric Source: IPCC 2007; Fuglestvedt et al. 2010 UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  11. 60 High F Gases N2O 26%  27%  CH4 50 CO2 40 30 20 10 0 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 Impact of choice of metric Global total CO2e emissions per year GWP100 GTP100 UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  12. 12 CO2e emissions per year High F gases 160%  193%  Larger increase N2O 10 CH4 CO2 Smaller increase 8 8.5%  7.8 %  Smaller decrease 8.2%  7.2%  6 4 Stronger decrease 7.9%  16%  2 0 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 1990 2008 Impact of choice of metric GWP GWP GWP GWP GTP GTP GTP GTP China USA EU27 Brazil UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  13. Value choices affect metrics • Policy goals, e.g. 2°C, emission trading • What’s included in the basket of gases • Revisions due to new evidence, e.g. SAR to AR4 • Choice of metric, e.g. GWP, GTP or other? • Choice of time horizon UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  14. 80 GWP 70 GTP 60 50 Metric value 40 30 20 10 0 0 100 200 300 400 500 Time Horizon (years) Impact of choice of time horizon:e.g. methane Data source: IPCC, 2007; Fuglestvedt, et al. 2010 UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  15. High F gases 70 N2O CH4 60 CO2 50 40 30 20 10 0 20 years 100 years 20 years 100 years Impact of choice of time horizon Global emissions in 2008 (CO2e) GWP GTP UNCERTAINTIES IN IMPLEMENTATION OF METRICS

  16. Conclusions • Both GWP and GTP require value choices. • Large sensitivity to choice of time horizon. • Important to consult IPCC Fifth Assessment Report related to status of scientific findings related to metrics • Next step: consider economic implications. • Any value in changing metric when impact on other areas unknown? UNCERTAINTIES IN IMPLEMENTATION OF METRICS

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