Energy-relevant Impacts of Climate Change in the Pacific Northwest


Mote, P.W., Salathé, E.P., Peacock, C. 2006. Energy-relevant Impacts of Climate Change in the Pacific Northwest. Report prepared for Portland General Electric by the Climate Impacts Group, University of Washington, Seattle. 19 pp.


Observations show substantial warming (1.5°F) in the Pacific Northwest, and indeed the entirety of western North America, over the past 50-100 years. Concomitant hydrologic changes toward earlier peak flow, reduced summer flow, and increased winter flow have also been observed and are several lines of evidence show that warming is responsible. Continued warming in the region is extremely likely because greenhouse gases are rising. We have examined 20 scenarios from state-of-the-art climate models and summarize here the changes they project. The average warming rate in the Pacific Northwest during the next century is expected to be in the range 0.1-0.6°C (0.2-1.0°F) per decade, with a best estimate of 0.3°C (0.5°F) per decade. Present-day patterns of greenhouse gas emissions constrain the rate of change of temperature for the next few decades: humans are committed to some degree of additional climate change. Beyond mid-century, the projections of warming depend increasingly on emissions in the next few decades and hence on actions that would limit or increase emissions.

Projected precipitation changes are modest, and are unlikely to be distinguishable from natural variability until late in the 21st century. Most models have winter precipitation increasing and summer precipitation decreasing. The aggregate changes in climate will likely produce continued decreases in June-September flow in most rivers in the Northwest, with increases in winter flow. However, changes in wind energy potential will probably be small. This report was prepared by the Climate Impacts Group for Portland General Electric.