Past and Future Trends in PNW Climate

Both PNW temperature and precipitation have increased over the 20th century (Figure 4 and Figure 5). On average, the region warmed about 1.5°F (0.83°C); warming was largest west of the Cascades during winter and spring. The largest relative increases in precipitation occurred in eastern Washington and southern British Columbia, mainly in spring. There is good reason to expect warming to continue as a result of climate change, with a likely warming rate of about 0.5°F (0.27°C)/decade. While future changes in precipitation are less certain, overall, precipitation is projected to increase in the PNW. These changes have significant implications for the natural resources of the PNW, as well as the human systems that depend on them. Much of the CIG’s efforts focus on identifying both the likely nature of these impacts and strategies for decreasing the region’s vulnerability to these likely changes.

Figure 4 20th century trends in average annual temperature (1920-2000). Increases (decreases) are indicated with red (blue) dots. The size of the dot corresponds to the magnitude of change.

Figure 5 20th century trends in average annual precipitation (1920-2000). Increases (decreases) are indicated with blue (red) dots. The size of the dot corresponds to the magnitude of change.

Source:
http://cses.washington.edu/cig/pnwc/pnwc.shtml