Climate model suggests more rain in Northwest’s future

BELLINGHAM — In Skagit County, it’s hard to say if a change in weather patterns due to climate change would mean more Skagit River flooding. But researchers at the University of Washington predict climate change will bring more rain to the U.S. West Coast in the next century.

“It’s hard to say what’s going to happen locally … there’s a lot of uncertainty,” UW Atmospheric Sciences researcher Mark Warner said.

He is confident in the science behind climate change, but said the extent of its effects is hard to predict.

Warner shared his recent studies Thursday with students and faculty at Western Washington University as part of the university’s Huxley College of the Environment Speaker Series.

Combining and comparing 16 different weather prediction models used in various countries, Warner concluded that higher temperatures associated with climate change will move more water vapor through atmospheric rivers.

Those rivers send heavy, highelevation rain from the tropical equator to specific points along the coast. When they collide with mountains like the North Cascades they drop a lot of rain and can cause extreme weather events like flooding and landslides. Warner referenced the November 2006 flood that caused $36 million in damage at Mount Rainier National Park as an example.

The Huffington Post reported that a 2013 study suggests temperatures will rise an average of 4 degrees Celsius globally by the year 2100.

Warner explained that a 7.5 percent increase in atmospheric water vapor with every 1 degree amounts to a more than 200 percent increase in heavy rain events over a 30-year period when comparing 1970-99 records and 2070-99 projections at 13 locations Warner studied off the U.S. coastline.

He said the change may affect Skagit snow pack because of more winter rain and less snow. A declining snow pack could mean more water funneling into the river.

The result may be an increase in stream flow in the Skagit River during winter. But it may also mean lower stream flows during the summer because of a low snow pack, which can have effects on public utilities, water supplies and fish in the river.


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