A modeling study of effective radiative forcing and climate response due to increased methane concentration

摘要

An atmospheric general circulation model BCC_AGCM2.0 and observation data from ARIS were used to calculate the effective radiative forcing(ERF) due to increased methane concentration since pre-industrial times and its impacts on climate. The ERF of methane from 1750 to2011 was 0.46 W m^(-2)by taking it as a well-mixed greenhouse gas, and the inhomogeneity of methane increased its ERF by about 0.02 W m^(-2).The change of methane concentration since pre-industrial led to an increase of 0.31 C in global mean surface air temperature and 0.02 mm d 1in global mean precipitation. The warming was prominent over the middle and high latitudes of the Northern Hemisphere(with a maximum increase exceeding 1.4 C). The precipitation notably increased(maximum increase of 1.8 mm d^(-1)) over the ocean between 10 N and 20 N and significantly decreased(maximum decrease >e0.6 mm d^(-1)) between 10 S and 10 N. These changes caused a northward movement of precipitation cell in the Intertropical Convergence Zone(ITCZ). Cloud cover significantly increased(by approximately 4%) in the high latitudes in both hemispheres, and sharply decreased(by approximately 3%) in tropical areas.