Part III. How Will Climate Change Affect the Pacific Northwest?
Part III of, “The Straight Facts on Forests, Carbon, and Global Warming,” an Oregon Wild report.
While predicting the local weather is an uncertain science, climate prediction is actually more accurate because the focus is on large-scale trends rather than local details. We know that the planet as a whole is almost certain to become warmer on average, and scientists expect an acceleration of the hydrologic cycle as warmer temperatures lead to increased evaporation from the oceans and more transpiration from plants. However, the effects of climate change will not be uniform around the globe. Significant uncertainty remains about how global trends will express themselves regionally. Future climate in the Pacific Northwest is even more uncertain because of complex topography and uncertain changes in precipitation, but our close proximity to the moderating influence of the Pacific Ocean likely offers a slight buffer from climate extremes.
The Pacific Northwest should expect continued climate variability. Existing cycles of cool-wet winters and warm-dry summers will likely continue, though they will be superimposed on a warmer average climate. Both floods and droughts have been part of our past and will almost certainly be part of our future, and both will likely get worse, but we don’t know if these climate extremes will be expressed with more frequency or more intensity, or both.
It is reasonable to expect more precipitation, mostly during our existing wet seasons. More of our winter precipitation will fall as rain instead of snow, so storage of water in snowpacks will likely decrease (on average). We should expect milder winters, earlier melting of snow packs, earlier spring run-off, longer periods of summer low stream flow, and more drought1.
Importantly, earth’s biogeochemical systems are complex and not at equilibrium. There are many feedbacks that lead to non-linear behavior, so we should NOT expect climate changes to be slow and predictable. Small changes in CO2 and global temperature can lead to large and/or rapid changes in climate and ecosystems2. Accordingly, the rate of current and future global changes may be unprecedented, chaotic, and highly disruptive.
 Scientific Consensus Statement on the Likely Impacts of Climate Change on the Pacific Northwest http://inr.oregonstate.edu/download/climate_change_consensus_statement_final.pdf
 José A. Rial, Rogera. Pielke Sr., Martin Beniston, Martin Claussen, Josep Canadell, Peter Cox, Hermann Held, Nathalie De Noblet-Ducoudré, Ronald Prinn, James F. Reynolds And José D. Salas. 2004. Nonlinearities, Feedbacks And Critical Thresholds Within The Earth’s Climate System. Climatic Change 65: 11–38, 2004. http://blue.atmos.colostate.edu/publications/pdf/R-260.pdf