SALEM — Scientists are moderately confident droughts will be more severe for Western U.S. farmers by mid-century if global carbon emissions remain roughly the same for the next 30 years, according to a scientific panel sponsored by the United Nations.
Precipitation may actually increase, but higher temperatures will reduce snow cover and dry out soils, according to the newly released report by the Intergovernmental Panel on Climate Change.
Reacting to the report, University of Washington atmospheric scientist Cliff Mass said earlier this month that Northwest agriculture can adjust by storing more water for irrigators.
"We can deal with it with more reservoir capacity," he said. "We've been lazy. We've used the snowpack as a reservoir."
Global temperatures are about 2 degrees Fahrenheit higher compared to 1850-1900. The climate will warm about one more degree by mid-century, regardless of emission trends, according to the IPCC.
The IPCC estimates that late 21st century temperatures will be 2.5 to 7 degrees higher than pre-industrial averages, depending on future carbon output into the atmosphere.
Average temperatures would be 7 degrees higher if emissions double by 2050 and triple that by the end of the century, the IPCC projects.
That scenario's plausibility "has been debated in light of recent developments in the energy sector," according to the IPCC.
Under another high-emissions scenario, carbon output more than doubles by the end of the century. The IPCC estimates temperatures would then be about 6.5 degrees higher than pre-industrial averages.
A mid-range scenario projects emissions rising slightly for several more decades and increasing late-century temperatures by 4.8 degrees above the pre-industrial baseline.
Two scenarios project what might happen if carbon emissions are immediately cut.
If emissions are net zero by about 2075, late-century temperatures would be 3.24 degrees higher, the IPCC estimates.
The lowest-emissions scenario envisions net-zero carbon output by about 2050. By late-century, global average temperatures would be 2.5 degrees above the pre-industrial standard.
U.S. Sen. Maria Cantwell, D-Wash., said in a statement the report should spur taxing carbon and spending more on "clean energy."
"This groundbreaking report makes it clear that the extreme weather now being felt around the globe and across Washington state will look mild compared to what’s ahead if we don’t act," she said.
"The next generation deserves to be able to enjoy the bliss of a Puget Sound summer day, not be trapped inside by triple-digit temperatures and smoky skies," Cantwell said.
Mass said the report largely echoes studies done over the past 20 years and shows that global warning is "not an existential threat."
"The world isn't going to end," he said. "The report's really quite underwhelming. It's not as hyped as the headlines."
The IPCC divided North America into six regions. Oregon, Washington, Idaho and California were grouped with the Southwest and Plains states.
Under any emissions scenario, scientists have "low confidence" the West will have more severe meteorological droughts caused by a lack of rain.
Scientists, however, have "medium confidence" that agricultural droughts caused by soil-moisture deficits will be more severe by mid-century and late century under the mid- or high-emissions scenarios.
Scientists have "low confidence" that agricultural droughts will be more severe under the lowest-emissions scenario.
Scientists also have "medium confidence" that human-influenced climate change has increased weather conducive to wildfires in the West.