Radiative forcing by anthropogenic surface albedo change from 1750 to 1990

Abstract

A radiative transfer model was used within a GCM to simulate the global shortwave radiation budget with natural vegetation cover and with the vegetation estimated for 1750, 1850, 1900, 1950 and 1990. Relative to the natural vegetation state, the global mean shortwave radiative forcing due to land cover change by 1750 was simulated as –0.06 Wm-2. The local forcing reached –2 Wm-2 over Europe, China and India, indicating a significant cooling influence on climate through agricultural activity before fossil fuel burning began. The description of the pre-industrial climate as “pre-anthropogenic” is therefore inappropriate. The global forcing simulated at 1990 relative to 1750 was –0.18 Wm-2, of comparable magnitude with estimated forcings due to aerosols, ozone, and solar variability. Climate model simulations intended for the detection and attribution of climate change should therefore include changes in surface albedo.