Modelling the Impact of Radiation Changes on the Terrestrial Carbon Sink - over the 1900-2100 period

Solar Radiation is one of the main requirements for plant functioning and any changes in this field are likely to affect plant photosynthesis. Changes in the solar radiation reaching the land surface caused by aerosols emitted from volcanoes and various anthropogenic sources have occurred during the industrial era. The aim of this study is to estimate the impact of changes in radiation during the 1900-2100 period on land productivity and carbon storage. We use an offline version of the land surface scheme of the Hadley centre model (Cox et al. 1998) which has been modified to account for variations of direct and diffuse radiation on sunlit and shaded canopy photosynthesis. Additionally, we use short wave and photosynthetic active radiation fields simulated by the Hadley centre climate model which takes into account the scattering and absorption of light by tropospheric and stratospheric aerosols. We describe the simulation of the land carbon cycle through the Pinatubo event but also the dimming-brightening period, and diagnose the impact that changes in diffuse radiation had on the atmospheric [CO2] growth-rate. We will also discuss the implications of these results for the future land carbon-sink, under likely changes in the atmospheric aerosol loading.