Estimates of variations in radiative forcing for methane in the past and in the future
S.V. Akishina, A.S. Mikhailova, Yu.M. Timofeyev, N.N. Filippov
Saint Petersburg State University, St. Petersburg, Russia
Keywords: radiative forcing, methane, outgoing thermal radiation, MODTRAN
Abstract
We calculate CH4 radiative forcing from the analysis of outgoing thermal radiation (OTR) fluxes obtained by the MODTRAN radiative code for five climate atmospheric models and various methane concentrations (0.8, 1.8, and 2.5 ppm). OTR values decreased by ~ 0.15% compared to the pre-industrial era. Seasonal and spatial variations in OTR fluxes at current methane rates reach ~ 13%. To date, due to the increasing CH4 concentration in the Earth’s atmosphere, methane RF is estimated at between -0.482 and -0.266 W/m2.
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