THE POTENTIAL IMPACTS OF GLOBAL WARMING ON THE PACIFIC NORTHWEST
Critical Findings for Washington and Oregon from the First National
Assessment of the Potential Consequences of Climate Variability and Change

Climate change and the Pacific Northwest

Despite its reputation for rain, the Pacific Northwest (PNW) experiences dry summers, and irrigated agriculture, urban users, and ecosystems rely on snowmelt for summer water. This fact is critical in understanding how the region responds to climate.
Year-to-year and decade-to-decade variations in PNW climate are influenced by two patterns of Pacific climate variability: El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). ENSO and PDO each tend to push PNW climate toward one of two main patterns: cool-wet or warm-dry.

Impacts of climate variations on the Northwest. The top panel shows the impacts of sea surface temperature (SST) conditions over the North Pacific associated with the warm phase of ENSO or PDO, and the bottom panel shows the impacts of the cool phase.

The warm-dry winters have thinner snowpack and lower spring and summer streamflow, with generally negative impacts on salmon and forests. The cool-wet winters have the opposite effects. Even though the annual temperature and precipitation fluctuations associated with the PDO (Figure 2) are fairly small, these small changes in climate have large impacts on the region's natural resources.


Natural Columbia River flow at present (dashed), and in 2050 as simulated under future climate conditions from four climate models.

During the past 100 years, the PNW has become warmer and wetter. The region's average temperature has increased 1.5 degrees F, and average precipitation has increased about 15%. Scientists cannot be sure what has caused these increases, but the increases are consistent with trends generated by climate models using observed increases in carbon dioxide. Climate models project continued increases in temperature and winter precipitation. Summer precipitation could go up or down.

What effects will these climatic changes have?
For the PNW, the most significant consequence of climate change is likely to be the reduction in all-important summer water supply. As the climate warms, snowpack will shrink and summer streamflow will drop considerably. This and other climate changes will have a wide range of consequences, most of them negative, for humans and ecosystems.

Even though water will become less plentiful in summer, higher winter precipitation (as occurred during the winter of 1998-99) will probably also increase wintertime flooding in many rivers.

Coasts
Both the physical landscape and the ecosystems of the coasts will be affected by climate change and rising sea level. Changes in wave direction may increase coastal erosion, as often happens during El Niño events. Increased winter precipitation will probably lead to more frequent landslides; recent wet winters have shown that thousands of homes are at risk from landslides around Puget Sound and on the Oregon coast, and climate models consistently project wetter winters.

What would we have to do to prepare for a changing climate?

Climate scientists agree that further climate change may be inevitable and will therefore require adaptation, although most scientists also think that the pace of climate change can be slowed by substantially reducing greenhouse gas emissions. This would give governments, businesses, and ecosystems around the world more time to respond and adapt to climate change as well as reducing the overall severity of climate change-related impacts, thereby buying "insurance" for an uncertain future. Another way to buy insurance now is to incorporate climate change into all long-term decisions about natural resources, thereby providing greater resilience.

Climate change is sure to occur in some form. Though the details are not yet clear, we know enough already to begin planning. With few exceptions, natural resources are managed as if climate were constant. Recent experience with year-to-year climate variations, like those associated with El Niño, provides some practice at dealing with years when climate is different from normal.  In years ahead we will see a change in the definition of normal.  The single most important thing that the region can do to prepare for a changing climate is to develop a dialogue between scientists and decision-makers. An increased awareness of how climate affects the region will increase resilience to climate variations and change. In addition, we can reduce local pressures on our resources and ecosystems.

Coasts
A wide range of coastal problems could be dealt with by changing land-use controls, construction setbacks, and zoning. Public funds could be better spent in ways other than subsidizing coastal development (especially re-development after damage) in obviously hazardous places.

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The following organizations produced this website:
Environmental Defense Natural Resources Defense Council Union of Concerned Scientists	National Environmental Trust World Resources Institute World Wildlife Fund
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Source:
http://www.climatehotmap.org/impacts/pacificnw.html