1. Climatic sensibility of Brazilian Earth System Model integration submitted to abruptly CO 2 drive The objetive, data and methology: So the purpose of this work is analyze the climatic sensitivity response of the BESM (version 2.5) when exposed to abrupt CO 2 changes. This study will help to understand the changed climate characteristics when the model is submitted to an abruptly CO2 concentration. There are two 30 years experiments of the BESM model, from 2007 to 2036, both of runs start from a 150 years spin-up, but one integration has the preindustrial values (280 ppmv) and the other has abrupt (1200 ppmv) atmospheric CO 2 concentration. There are two (abruptly and preindustrial CO2 concentrations) 30 years (1971-2000) from Community Climate System Model (CCSM4) (Gent et al., 2011) of the National Center of Atmosphere Research (NCAR) and finally two others with 30 years (271-300) integrations (abruptly and preindustrial CO2 concentrations) from the ESM2M model (Earth System Model 2) (Dunne et al., 2012) of the Geophysical Fluid Dynamics Laboratory (GFDL). For all models integrations will be calculated Consecutive Dry Days (CDD), R95p (Extre me wet days), total precipitation (PRCTOT) CLIMDEX indexes (http://etccdi.pacificclimate.org/software.shtml). Will be calculated CLIMDEX indexes differences of abruptly (1200 ppmv) and not abruptly (280 ppmv) integrations. All the CLIMDEX indexes differences will compared to each other model.http://etccdi.pacificclimate.org/software.shtml Thanks to rede clima for it support Dr. Jose Fernando Pesquero – fernando.pesquero@inpe.br Dr. Paulo Nobre – paulo.nobre@cptec.inpe.br Centre for Weather Forecasting and Climate Research (CPTEC) Results: When submitted to one abruptly CO2 integration all the models show very similar climate patterns for 30 years of integration. The results do not have to show identical results, because are different models and different periods. One climate precipitation pattern of all the models only for Brazil could be with Southern, Southeatern, Midwestern Regions of Brazil with precipitation above the normal, and the rest of Brazil very drought climate scenario. Another climate patterns could be: a) South of Midwestern and Sothern Brazil Region: the results show precipitations increases, like the PRCTOT and the R95p. Do do not change the CDD indexes. b) Southeastern, central and north of Midwestern Regions of Brazil: increase of the PRCTOT, R95p and the CDD. Intense storms during the rainy season. For all the South America the pattern was very drought climate pattern over northern of South America and precipitation above the normal in any other South America Region. Due to the CDD profile does not show a water increase, it consequently contributes to accelerate the river and water reservoir evaporations in most areas of the Brazil. The agricultural areas over the Brazilian Southern Region will not have a significant CDD extreme climate change, because the values are only around from 1 to 5 days. When analyzing together the figures 1 and 2, over Southeastern and east and south Midwestern Regions of Brazil, both of regions have increase long dry day periods and so increase the precipitation. So, the precipitation when occur will possibly be as terrible intense storms. Finally, decreases the number of intense storms over the Northern of South America. Can be conclude that the BESM model responded correctly to abruptly CO2 integrations.