Accounting for the climate-carbon feedback in emission metrics
Thomas Gasser1,2,a, Glen P. Peters2, Jan S. Fuglestvedt2, William J. Collins3, Drew T. Shindell4, and Philippe Ciais11Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, Université Paris-Saclay, CEA – CNRS – UVSQ, 91191 Gif-sur-Yvette, France 2Center for International Climate and Environmental Research – Oslo (CICERO), 0349 Oslo, Norway 3Department of Meteorology, University of Reading, Reading, RG6 6BB, UK 4Nicholas School of the Environment, Duke University, Durham, NC 27708, USA anow at: International Institute for Applied Systems Analysis (IIASA), 2361 Laxenburg, Austria
Received: 04 Nov 2016 – Accepted for review: 09 Nov 2016 – Discussion started: 10 Nov 2016
Abstract. Most emission metrics have previously been inconsistently estimated by including the climate-carbon feedback for the reference gas (i.e. CO2) but not the other species (e.g. CH4). In the fifth assessment report of the IPCC, a first attempt was made to consistently account for the climate-carbon feedback in emission metrics. This attempt was based on only one study, and therefore the IPCC presented tentative values and concluded that more research was needed. Here, we carry out this research. First, using the simple carbon-climate model OSCAR v2.2, we establish a new impulse response function for the climate-carbon feedback. Second, we use this impulse response function to provide new estimates for the two most usual metrics: Global Warming Potential (GWP) and Global Temperature change Potential (GTP). We find that, when the climate-carbon feedback is correctly accounted for, the emission metrics of non-CO2 species increase, but in most cases not as much as initially indicated by IPCC. We also find that, when the feedback is removed for both the reference and studied species, the metric values only have modest changes, compared to when the feedback is included. However, including carbon-climate feedbacks, particularly in absolute metrics or for short time horizons, gives a more realistic representation of the response.
Gasser, T., Peters, G. P., Fuglestvedt, J. S., Collins, W. J., Shindell, D. T., and Ciais, P.: Accounting for the climate-carbon feedback in emission metrics, Earth Syst. Dynam. Discuss., doi:10.5194/esd-2016-55, in review, 2016.