Puget Sound area may see more flooding as climate warms, UW study finds

Flooding could be come increasingly common in the Puget Sound region as the climate warms, according to a new University of Washington study.
Flooding could be come increasingly common in the Puget Sound region as the climate warms, according to a new University of Washington study. The Peninsula Gateway file, 2012

A University of Washington climate-change study for the Puget Sound area forecasts a temperature rise of 2.9 to 5.4 degrees Fahrenheit by mid-century, resulting in wide-ranging shifts as more storms bring rain rather than snow.

A warming climate is expected to result in an increase in flood risks even as overall precipitation is predicted to remain roughly the same. The climate models indicate more rain will fall during the winter when rivers already are at higher levels, and intense storms will become more frequent.

Sea-level rise also can contribute to flooding as storm surges become a bigger threat.

“Flooding is a big story here,” said Guillaume Mauger, a UW climate researcher who is a lead author of the report. “The models are getting a lot more consistent.”

The study, released Tuesday, updates a 2005 report and was prepared for the Puget Sound Partnership and the National Oceanic and Atmospheric Administration. The document reflects a decade of additional research into the regional effects of climate change that includes some new areas.

The report, for example, finds that the Puget Sound region is expected to experience more frequent landslides and increased erosion due to more heavy rainfall.

It also delves into the effects on marine life from ocean acidification caused by increasing levels of carbon dioxide.

The report also lays out the wide range of uncertainties about the region’s climate change future.

Sea levels are expected to rise. But the potential higher levels in Seattle, for example, range from 4 to 56 inches. The big range of possibilities largely reflect the wide differences in projections in how fast the ice will melt in Greenland and Antarctica.

Another big unknown is the extent to which the world will succeed in curbing fossil-fuel emissions that drive climate change, a topic that will be the focal point of an international conference that begins Nov. 30 in Paris.

Any major reductions in curbing carbon emissions during the next few decades won’t make much of a difference in what happens to the climate through mid-century.

That’s because most of the emissions that influence these changes already have been released. But in the last half of the century, these reductions could help slow the rate of the warming.

Even as the effects of climate change amplify, the study notes there will continue to be plenty of natural variability of wetter and drier years.

There also will be longer term trends because of major weather influences such as La Niña, which is caused by unusually low ocean temperatures in the equatorial Pacific.