Methane mitigation shows significant benefits towards achieving the 1.5 degree target.
Abstract
Most analyses of allowable carbon emissions to achieve the 1.5 degree target implicitly assume that the ratio of CO2 to non-CO2 greenhouse gases remains near constant, and that all radiative forcing factors have similar impacts on land and ocean carbon storage. Here we determine how plausible reductions in methane emissions will make the carbon targets more feasible. We account for the latest estimates of the methane radiative effect as well as the indirect effects of methane on ozone. We particularly address the differing effects of methane and CO2 mitigation on the land carbon storage including via reduced concentrations of surface ozone. The methodology uses an intermediate complexity climate model (IMOGEN) coupled to a land surface model (JULES) which represents the details of the terrestrial carbon cycle. The carbon emissions inputs to IMOGEN are varied to find allowable pathways consistent with the Paris 1.5 K or 2.0 K targets. The IMOGEN physical parameters are altered to represent the climate characteristics of 38 CMIP5 models (such as climate sensitivity) to provide bounds on the range of allowable CO2 emissions. We examine the effects of three different methane mitigation options that are broadly consistent with the ranges in the SSP scenarios: little mitigation, cost-optimal mitigation, and maximal mitigation. The land and ocean carbon storage increases with methane mitigation, allowing more flexibility in CO2 emission reduction. This is mostly since CO2 fertilisation is reduced less with high methane mitigation, with a small contribution from reduced plant damage with lower surface ozone levels.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMGC52A..02C
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0498 General or miscellaneous;
- BIOGEOSCIENCES;
- 1699 General or miscellaneous;
- GLOBAL CHANGE;
- 6349 General or miscellaneous;
- POLICY SCIENCES