Precipitation Trends 1900-2005 Over the Globe from Reconstruction and Coupled Model Simulations

The global precipitation trend in the 20th century is evaluated using our historical precipitation reconstruction and the CMIP3 and CMIP5 model simulations. A significant increasing trend of the global oceanic mean was found in both reconstruction and models. The tendency in the historical reconstruction (0.04 mm day-1 over 100 years) is about twice that of the mean tendency among the models over oceans. Over land the spatial patterns of the trends in the reconstruction and the models are similar to those shown in the IPCC AR4 reports. Over the oceans, they both generally show a positive trend in the equatorial and subpolar regions and negative trends over the subtropics. The largest oceanic differences are near the equator (10°S to 10°N). The seasonal differences in the spatial patterns of the trends in the reconstruction and models appear to indicate greater positive trends in wet than dry seasons, particularly in monsoon regions including the Southeast Asian, Australian-Asian monsoons. We also investigated the CMIP5 future simulations and found that models project a continuing and stronger increasing tendency in the 21th century of the global mean precipitation.