Future PNW Region Climate Scenarios and Their Impacts on Aquatic Habitats in Historical Context

As part of an ongoing assessment of climate impacts on natural resources in the Pacific Northwest (PNW) region, the University of Washington's Climate Impacts Group has developed future scenarios for climate and hydrology across much of the western US. Starting with downscaled climate scenarios from the global climate model simulations used in the IPCC's Fourth Assessment report, we present 21st century scenarios for temperature, precipitation, and impacts on hydrologic parameters in the context of observed and/or simulated variations in these parameters for the past century. Some of these scenarios suggest that many important features of the PNW's rivers, including summer low flows, daily peak flows, and stream temperatures, may enter regimes unlike any observed in the past century by the mid to late 21st century.