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Northwest climate change report: Shrinking snowpacks, drier summers

Northwest climate change report: Shrinking snowpacks, drier summers
FILE - In this Jan. 31, 2012 file photo, Natural Resources Conservation Service employees Chris Mundy, front, and Nicholle Kovach measure snow depth at a site near Wanoga Snoplay Area west of Bend, Ore. (AP Photo/The Bulletin, Rob Kerr)

Tuesday was a big day in the science community with the release of a major federal scientific report on climate change.

The 840-page report, several years in the making, looks at regional and state-level effects of global warming, compared with recent reports from the United Nations that lumped all of North America together. A draft of the report was released in January 2013, but this version has been reviewed by more scientists, the National Academy of Science and 13 government agencies and had public comment.

It is written in a bit more simple language so people could realize "that there's a new source of risk in their lives," said study lead author Gary Yohe of Wesleyan University in Connecticut.

The report breaks the nation down into 8 geographical regions, including the Pacific Northwest, which for their report encompasses Washington, Oregon and Idaho.

The report does do a much better job of translating incredibly complex scientific research into something the general public can benefit from -- something that has been missing in the debate thus far and a very important feat in a world where there are thousands of voices -- some who know what they're talking about; some who have no business claiming expertise about it -- clamoring on the subject that has become dangerously politicized.

What's already happened:

The report states that temperatures across the Pacific Northwest are averaging about 1.3 degrees warmer now than they were in 1895, with the most notable rise in winter (the other three seasons' rises were much less significant.)

The report does note there has been a slight increase in the number of heat waves over the past century, with that number at 70 percent above the long term average over the past 20 years, with 5 of the top 10 regional heat waves happening in the past 20 years.

On the other hand, there has been a slight decrease in the frequency of cold waves over the past century with all of the top 10 regional cold snaps occurring before 1991.

As for precipitation, the reports states that rainfall has generally increased a little but trends are small with respect to natural variability and there hasn't been any statistically significant overall changes found.

What's expected to happen:

The simulations the report used were based on various assumptions about future human activity and CO2 emissions, but all show some warming (See map here). Southeastern Idaho would feel the most warming in the Northwest, while the coastal regions would see the least due to proximity to the chilly Pacific Ocean, but all areas would warm somewhat. Using the lesser emission scenario, Washington would warm about 1.5 degrees in 2021-2050, then 2.5 degrees into the 2041-2070 time frame, and about 3.5 degrees in the 2070-2099 time frame.

If you use the more aggressive emissions scenario, the I-5 corridor could warm 3.5 degrees by mid century and 5-6 degrees by the end of the century while southeast Idaho could be 8.5-9.5 degrees warmer.

The models also suggests the Willamette Valley, southern Oregon, much of Eastern Washington and particularly southern Idaho could see a marked increase in number of days each year with high temperatures and 95 degrees or warmer.

On the flip side, the freeze-free period across the region is forecast to increase by 25-35 days, perhaps even more than 40 days shorter in Western Washington and Oregon.

As for rainfall, the model simulations for the Northwest aren't as decisive. There is a general theme that it could end up a little wetter in Washington in the fall and winter but not significantly so. The models also don't seem to indicate there would be a noticeable increase in extreme precipitation events in our region.

There is, however, a better signal that summers would be drier, perhaps as much as 10 percent across the region.

Biggest climate change impact: Our mountain snowpack

One of the region's most critical dependencies is on our mountain snowpack. The mountains are a critical water bank that as the snow melts in the spring, powers our region's rivers and economy. That snow melt doesn't just simply let us get a glass of water at night and water our lawns in July, it supplies crucial irrigation supplies for our vast agricultural landscape and also provides 40 percent of the nation's total of hydroelectricity. It also provides for our expansive fish, wildlife and forested ecosystems.

The report says human activities have already strained our water supplies to where there are big conflicts between those who depend on water supplies in dry years, and those dry periods will become more frequent and extended as the century progresses.

The report that the average projected decrease in summer precipitation is about 10 percent could have a large effect on frequency and intensity of wildfires and lack of water for agricultural purposes (to say nothing of our ski industry.)

Average snowpack on April 1 has already decreased about 20 percent since 1950, the report states, with spring snow melt occurring between 0 and 30 days earlier, depending on location (although the last few years have had healthy snowpacks in Western Washington and later than usual snow melts.)

The report states that by 2050, snow melt is projected to begin 3-4 weeks earlier than the 20th Century average, leaving summer flows substantially lower. The reduced flows will require more tradeoffs among those who need the water, such as hydroelectricity generation, city reservoirs and agricultural irrigation demands. The economic impact of reduced hydroelectric power could be hundreds of millions of dollars per year, the report states. And reduced river flows could severely impact salmon runs.

As for agriculture, the report says the risk of a water-short year, for example as when Yakima basin junior water rights holders are allowed only 75% of their water right amount, is projected to increase from 14% in the late 20th century to 32% by 2020 and 77% by 2080, assuming no emission adaptations.

Coastal vulnerabilities

Rising sea levels are also a concern of a warming planet as glacial melt occurs. The Pacific Northwest is in a bit of a unique situation in that the coast is ever-so-gradually rising due to tectonic shifts, so the sea level rises so far have been counterbalanced a bit by rising land -- although the report warns that will change after the next great subsidence quake offshore that occur every few hundred years and the coast may drop as much as 40 inches or more relative to sea level.

But even taking these factors into consideration, projections shows sea level rises around 2 feet by the end of the century. Strong warming El Nino conditions can add as much as 4-12 inches to sea levels for several months.

The report states that as sea levels rise, areas within 3.3 feet in elevation of high tide will be inundated more frequently and coastal wetlands and beaches will decline in quality. Ocean acidification will also affect marine species and warming ocean surface temperatures -- perhaps as much as 2.2 degrees by mid century, the report states -- will also affect marine life.

And finally, rising waters could affect property owners along coastal waterfronts, threaten wastewater treatment plants, ferry terminals and coastal road and rail transportation, the report states.

Forest Impacts

The report indicates change in climate will also damage our forests, from increasing wildfires to insect outbreaks and tree diseases, "virtually certain to cause additional forest mortality by the 2040s and long-term transformation of forest landscapes."

And if you go with the high emissions scenarios, the report projects the region will undergo extensive conversion from subalpine forests to other forest types by the 2080s.

As for wildfires, with hotter, drier summers, the mean annual area burned in the Northwest is expected to quadruple, and the probability that 2.2 million acres would burn each year across the Northwest would rise from 5 percent to 50 percent.

Hopefully this report helps "clear the air" a bit on the complex and politicized, but important subject. I've only scratched the surface on the report -- the full report can be found online and is broken down into highlights and the full-fledged report.

Dealing with climate change is not something the United States can do alone, but we can take the lead in having a honest and scientifically sound debate on its merits and what can be done to help mitigate its effects.

As the report states: "The cumulative weight of the scientific evidence contained in this report confirms that climate change is affecting the American people now, and that choices we make will affect our future and that of future generations."

For More Information:

* National Climate Assessment Home Page
* National Report Highlights
* Full National Report
* Northwest Region Highlights
* Northwest Region Full Report
* Northwest Climate Change Statistical Data