Validation Study for Precipitation and Surface Temperature in Mexico and Their Estimation for the XXI Century

Nowadays it is known that in order to estimate whatever climate change impact for a given region, it is necessary to work with the results of the ensemble of coupled GCM simulations, especially those that recently participated for the IPCC 4th Assessment Report. However, it is also a known fact that we will have better confidence on those model estimations for the future if we can observe that they are able to reproduce at least the main large scale features of the present-day climatology. A validation study is performed here for the results of that ensemble of models in Mexico in the case of surface temperature and precipitation during the period 1961-1990. We compare the model results with the Climate Research Unit databases for that period, and check whether the models are able or not to reproduce the main large-scale features of precipitation and surface temperature around Mexico. Based on the above results we analyze the XXI Century large time simulations of the ensemble of 23 models for the SRES-A1B and SRES- A2 scenarios and try to look for possible spatial and temporal variations in precipitation and surface temperature in the region. We are also currently working with another approach of making the ensemble of models, the Reliability Ensemble Averaging (REA) method of Giorgi and Mearns (2002), instead of just taking the simple model average. The REA method takes into account the ability of the model in reproducing present-day climate and the convergence of the simulated changes across models to make the ensemble. We will present preliminary results of the comparison between both the simple-average and the REA methods for Mexico.