Climate Sensitivity to Absorbing Tropospheric Aerosols in Experiments With a General Circulation Model

Columbia University, New York NY

Investigators

Abstract

Direct radiative forcing by absorbing tropospheric aerosols such as carbonaceous and soil dust aerosols is one of the most uncertain factors in climate change. The main objective of this project is to improve understanding of the climate response to forcing by these absorbing tropospheric aerosols for present day conditions. The PI will conduct sensitivity experiments using the NASA Goddard Institute of Space Studies General Circulation Model (GCM), plus other GCMs as available and as time and resources allow, e.g., the Community Climate System Model. He will analyze the response of main climate variables such as surface temperature, precipitation, cloud cover, sea level pressure and geopotential height on the global scale. Global and zonal averages, the horizontal patterns and the variability in time of these variables between different experiments as well as between experiments and observations, will be compared. From these analyses, the PI will draw conclusions about the uncertainty, both in the spatial structure and in the magnitude of the climate response in simulations of the present day climate due to the uncertainty in the radiative parameters and the vertical distribution of the absorbing tropospheric aerosols. The PI will also estimate what accuracy of these parameters is necessary to obtain reliable results from climate simulations with carbonaceous and soil dust aerosols. This research is important because atmospheric aerosols strongly impact the atmosphere's radiation budget and new knowledge about aerosol-radiation interactions will improve the ability of climate modelers to project future climates.