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Table 2 GWPs for methane in IPCC assessment reports (ARs)

From: Rethinking methane from animal agriculture

  Lifetime (year) GWP20 GWP100 Descriptions
AR1 10 63 21 Determined GWP of CH4 by including indirect effects on stratospheric water vapor, CO2 and tropospheric ozone
SAR 12 56 21 Updated estimates of atmospheric lifetimes, molecular RF factors, and representation of the carbon cycle
TAR 12 62 23 Decreased RF per kg of CO2 by 12%
AR4 12 72 25 Included climate-carbon feedbacks for calculating AGWP of CO2 based on Plattner et al. (2008). Increased the direct RF of CH4 by 25% (due to tropospheric ozone) and 15% (due to stratospheric H2O vapor)
AR5 12.4 84 (85)a 28 (30) Included climate-carbon feedbacks for calculating the AGWP of CO2 based on Joos et al. (2013)
86 (87) 34 (36) Included climate-carbon feedbacks for calculating the AGWPs of both CO2 and CH4
  1. AR1, the first IPCC assessment report (IPCC 1990); SAR, the second IPCC assessment report (IPCC 1995); TAR, the third IPCC assessment report (IPCC 2001); AR4, the fourth IPCC assessment report (IPCC 2007); AR5, the fifth IPCC assessment report (IPCC 2013)
  2. aGWP values in and out of the parentheses are for biogenic and fossil CH4, respectively
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CABI Agriculture and Bioscience

ISSN: 2662-4044