[A-AS05] [EE] Contributions of local and long-range transport to air pollutants in mega-cities

[AAS05-P04] A modeling study of effective radiative forcing and climate response due to increased methane concentration

*Bing Xie^1,2, Hua Zhang^1,2, Dong-dong Yang³, Zhi-li Wang⁴ (1.Laboratory for Climate Studies of China Meteorological Administration, National Climate Center, China Meteorological Administration, 2.Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, 3.College of Atmospheric Science, Nanjing University of Information Science & Technology, 4.State Key Laboratory of Severe Weather & Key Laboratory of Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences)

Keywords:Methane, Effective radiative forcing, Climate change

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 to 2011 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⁻¹ in 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 >–0.6 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.