AOGCM SIMULATIONS OF CLIMATE CHANGE IN THE NORTHEAST US OVER THE LAST 100 AND NEXT 100 YEARS

Climate projections derived from atmosphere-ocean global circulation models (AOGCMs) are the cornerstone for assessing the potential impacts of climate change at the regional scale. However, before assessing change in the future, output from climate models should be analyzed to determine how well the models recreate past climate variability and change in the region of interest. Here, we systematically compare observed climate over the U.S. Northeast with past simulations from eight global circulation models to determine the degree to which global models are able to simulate surface climate in the NE. This analysis shows that historical AOGCM simulations are able to reproduce past annual temperature trends across the NE over the past 100 years, although significantly under- estimating the winter warming observed over the past 30 years. Representative statistical and dynamical downscaling methods capture the general spatial and temporal gradients of temperature and precipitation across the region. We then develop projections of future climate change in the NE using those AOGCMs that reproduce the observed climate variability and change over the last 100 years. The primary changes projected to occur over the next century - slightly greater temperature increases in summer than winter, and increases in winter precipitation - are consistent with projected trends in regional climate processes and are relatively independent of model or scale. These suggest confidence in the direction and potential range of the most notable regional climate trends, with the absolute magnitude of change depending on both the sensitivity of the climate system to human forcing as well as on human emissions over coming decades.