Since at least 2015, when President Obama signed the Paris Climate Accord, 3.6 degrees Farenheit has served as an important threshold.

That’s the amount of average global warming scientists agree, if reached or eclipsed by 2100, will likely cause an irreversible cascade of climate change-induced extreme weather events — including droughts, heat waves and more intense wildfire seasons.

According to a nationwide analysis of weather data by the Washington Post, some places in the continental United States have already passed that threshold. On the newspaper’s heat map of the country, deep red spots fleck the Northeast and along the country’s northern border. A pool of heat encompasses the city of Los Angeles and a huge splotch of warmth sits squarely over the Rocky Mountains.

And two of the fastest warming counties in the country are in Southeastern Oregon.

But just focusing on those two areas — Lake and Harney counties, which have seen increases of 3.8 and 3.9 degrees Farenheit, respectively, since the early 20th century — ignores the significant warming that is taking place throughout the region, said Phil Mote, dean of the graduate school at Oregon State University and a longtime researcher of how climate change is affecting the Pacific Northwest.

The problem with looking at smaller areas, Mote said, is that, with smaller sample sizes, there is a greater chance for hiccups in the data. For Harney County, a vast area of high desert, there is only one weather data collection station, at the Malheur National Wildlife Refuge, so the chances for anomalies there are higher than for the entire region, which is blanketed by more than 100 stations.

With the exception of two data collection stations in Idaho, “every station in the region over the period of record has warmed and nearly every one of those is statistically significant,” Mote told The Oregonian/OregonLive.

While some of the warming can be explained by natural variability, including weather cycles like El Niño and La Niña, the amount of region-wide temperature increase can only be explained by human factors, namely the buildup of carbon dioxide in the atmosphere, Mote explained.

“There is no possible way to explain this warming with any combination of natural factors,” he said.

According to a weather data mapping tool maintained by the University of Washington, the average temperature in Oregon has gone up by 2.71 degrees Farenhiet since the early 20th century. For Montana, it’s jumped by 2.66 degrees. Washington and Idaho have each seen a rise of roughly 1.9 degrees.

A weather data analysis tool shows that nearly every weather station in the Pacific Northwest has seen a significant rise in average temperatures over the last century. Courtesy/University of Washington

A few degrees may not sound like much, but as the Washington Post reported, some effects are already being seen. In Rhode Island, which the newspaper said was the fastest-warming state in the continental United States, sea level rise is already eroding some beaches at a rate of 3 feet per year. In New Jersey, lakes that usually freeze solid early in the fall are freezing later and with thinner ice. In the Pacific Northwest, experts have forecast higher temperatures to lead to longer and more intense fire season, droughts and a lower snowpack in the mountains, which many residents rely on for water during the dry summer months.

The negative impacts of climate change will not affect everyone equally. Those on the margins — low-income communities, indigenous people, and those who depend heavily on natural resources — will be hit hardest by the coming changes.

The only way to avert the worst of the coming changes, nearly all scientists agree, is to drastically reduce our greenhouse gas emissions.

-- Kale Williams

kwilliams@oregonian.com

503-294-4048

@sfkale

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