Radiative Forcing and Climate Response Due to Black Carbon in Snow and Ice

The radiative forcing and climate response due to black carbon (BC)in snow and/or ice were investigated by integrating observed effects of BC onsnow/ice albedo into an atmospheric general circulation model(BCC_AGCM2.0.1) developed by the National Climate Center (NCC) of theChina Meteorological Administration (CMA). The results show that the globalannual mean surface radiative forcing due to BC in snow/ice is +0.042 Wm^-2, with maximum forcing found over the Tibetan Plateau and regional meanforcing exceeding +2.8 W m^-2. The global annual mean surface temperatureincreased 0.071^oC due to BC in snow/ice. Positive surface radiativeforcing was clearly shown in winter and spring and increased the surfacetemperature of snow/ice in the Northern Hemisphere. The surface temperatures ofsnow-covered areas of Eurasia and North America in winter (spring) increased by0.83^oC (0.6^oC) and 0.83^oC (0.46^oC), respectively.Snowmelt rates also increased greatly, leading to earlier snowmelt and peakrunoff times. With the rise of surface temperatures in the Arctic, more watervapor could be released into the atmosphere, allowing easier cloud formation,which could lead to higher thermal emittance in the Arctic. However, the totalcloud forcing could decrease due to increasing cloud cover, which will offsetsome of the positive feedback mechanism of the clouds.