Mechanisms of anthropogenic climate change in a simulation of the 20th century's climate with the LMDZ GCM with focus on aerosol indirect radiative effects
A way to understand human impact on the global-scale climate is to use general circulation models to simulate the climate of the past decades. The earth's climate has been increasingly well documented throughout the 20th century. Trends have been detected for different climate parameters such as the global annual mean surface temperature, cloud cover and precipitation. To understand the functionning of different anthropogenic forcings, we carried out a number of simulations with the LMD atmospheric GCM (LMDZ). SST and sea ice extent were prescribed from observational data. We carried out three ensembles of simulations. In the first ensemble, observed annual values for the atmospheric concentrations of five greenhouse gases (GHG), as well as 10 year-averaged distributions of sulfate aerosols deduced from time-varying emission data, were imposed. In the second ensemble, sulfate aerosols were fixed to a pre-industrial distribution. Finally, we carried out an ensemble of control simulations where both GHG and sulfate aerosols were fixed. We show the impact of GHG and aerosols on several quantities and examine the relative importance of the two different forcings. In particular, the functionning and impact on climate on global and regional scale of anthropogenic aerosol-induced modifications of clouds (the aerosol indirect effects) are examined. We show indications that, in our model, aerosol indirect effects seem to be important to explain climate change features at least on a regional scale.
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003