A NORTHEAST CLIMATE IMPACTS ASSESSMENT; REGIONAL PROJECTIONS AND PUBLIC OUTREACH

The Northeast Regional Climate Impacts Assessment explores the potential impacts of global climate change on the northeastern United States through analyses of output from climate model projections and the observational record. The regional-scale skill of nine coupled Atmosphere-Ocean General Circulation Models (AOGCMs) is tested by comparing trends and variations in hind-cast simulations with available instrumental data from across the region. Despite the relatively coarse grid-spacing of the AOGCMs, most models generally capture key aspects of regional atmospheric circulation. Trends and variations in regional temperature, rainfall, streamflow, and other climate indicators are also generally well simulated on seasonal to decadal time scales. A relatively high degree of confidence is placed on projected trends that are consistent with observed trends or that are otherwise expected in a warming world (e.g., fewer frost days in winter and earlier snow-melt in spring).

Two different sets of 21st century climate change projections are studied based on two future emissions scenarios. Not surprisingly, the emissions pathway often has a significant impact on the regional impacts that were simulated by the models. For example, AOGCM output downscaled by a regional hydrologic model projects that the timing of peak spring streamflow to occur 10 days earlier under the lower emissions scenario and more than two weeks earlier under the higher emissions scenario. Results from this and other regional-scale impact assessments suggest that confidence can be placed in the direction and potential range of some projected climate changes, while the absolute magnitude of those change depends on both the sensitivity of the climate system to human forcing as well as the emissions pathway.