About the Puget Sound Institute

Climate change
5. Observed increase in average annual temperature for the Pacific Northwest. The
Pacific Northwest warmed about +1.3°F between 1895 and 2011, with statisticallysignificant
warming occurring in all seasons except for spring (Kunkel et al., 2013; Mote
et al., 2013). This trend is robust: similar 20 th century trends are obtained using different
analytical approaches (Mote et al., 2003). All but five of the years from 1980 to 2011
were warmer than the 1901-1960 average (Mote et al., 2013). 10
6. Projected increase in annual average temperature for Puget Sound. Warming is
projected to continue throughout the 21 st century. For the 2050s (2041-2070) 11 relative
to 1970-1999, temperature is projected to rise +5.5°F (range: +4.3 to +7.1°F) for a high
greenhouse gas scenario (RCP 8.5). Much higher warming is possible after mid-century
(Mote et al., 2015). Lower emissions of greenhouse gases will result in less
warming.
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7. Ongoing variability. Natural variability will remain an important feature of global and
regional climate, at times amplifying or counteracting the long-term trends caused by
rising greenhouse gas emissions. Important modes of natural variability for the Pacific
Northwest include the El Niño/Southern Oscillation (i.e., El Niño and La Niña) and the
Pacific Decadal Oscillation.
8. The size of projected change is large compared to observed variability. The Pacific
Northwest is likely to regularly experience average annual temperatures by mid-century
that exceed what was observed in the 20th century. Specifically, all scenarios project
that, by mid-century (2041-2070), annual temperatures will be warmer than the
warmest year historically (1950-1999, Mote et al., 2013).
Precipitation
9. No change observed in annual precipitation for the Pacific Northwest. There is no
statistically significant trend toward wetter or drier conditions in Pacific Northwest
precipitation for the period 1895-2011. 10
10. Small changes projected for annual precipitation in Puget Sound. Projected changes in
total annual precipitation are small (relative to variability) 12 and show increases or
decreases depending on models, which project a change of −2 % to +13 % for the 2050s
(relative to 1970-1999, Mote et al., 2015). 9 11
11. Projected increase in precipitation extremes for Puget Sound. Heavy rainfall events are
projected to become more severe by mid-century. Specifically, the yearly maximum 24-
hour rainfall is projected to increase by +4% to +30% for the 2050s (relative to 1970-
11
Results are often cited for the “2050s” or “2080s”. These refer to the 30-year average centered on each decade
(2041-2070 and 2071-2100, respectively).
12
Year-to-year variations in precipitation are about ±10 to 15%, on average.
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