Evaluating uncertainties in the prediction of regional climate change

Uncertainties in regional climate change simulations for the 21st century b y five coupled atmosphere-ocean General Circulation Models (AOGCMs) (two of them including ensembles of simulations), for different anthropogenic forc ing scenarios and 23 regions in the World, are examined. Seasonally and reg ionally averaged precipitation and surface air temperature for the future p eriod of [2070-2099] as compared to the period of [1961-1990] are considere d. The dominant source of uncertainty in the simulation of average regional climate change is due to inter-model variability with inter-scenario and i nternal model variability playing secondary roles. The range of predicted c limate changes by different realizations of the same ensemble is small, and simulated changes exhibit a high level of coherency among different forcin g scenarios. Uncertainties in regional changes are 3 K or greater for tempe rature and 25% of present day values or greater for precipitation. The mode l biases in reproducing present day climate are less than or equal to 1 K t o over 5 K for temperature and less than or equal to 10%, to over 100% for precipitation.