Has global warming intensified 2017’s wildfires in the U.S. West? “When we remember that the relationship between temperature and fire is exponential, we’re really talking about a very different western United States in 50 years”

Desdemona Despair

By Robinson Meyer 
7 September 2017

(The Atlantic) – This wasn’t supposed to be a bad year for Western wildfires.

Last winter, a weak La Niña bloomed across the Pacific. It sent flume after flume of rain to North America and irrigated half the continent. Water penetrated deep into the soil of Western forests, and mammoth snowdrifts stacked up across the Sierra Nevadas. California’s drought ended in the washout.

Yet fires are now raging across the West. More than two dozen named firescurrently burn across Washington and Oregon. More than one million acres have burned in Montana, an area larger than Rhode Island, in the Treasure State’s third-worst fire season on record. And the largest brushfire in the history of Los Angeles currently threatens hundreds of homes in Burbank.

Canada may be experiencing an even worse year for wildfires: 2.86 million acres have burned in British Columbia, the largest area ever recorded in the province.

So what happened? How did a wet Western winter lead to a sky-choking summer?

The answer lies in the summer’s record-breaking heat, say wildfire experts. Days of near-100-degree-Fahrenheit temperatures cooked the Mountain West in early July, and a scorching heat wave lingered over the Pacific Northwest in early August.

“This will become an important year for [anecdotes about] the importance of temperature. Despite the fact that these forests were really soaked down this winter and spring, these heat waves have dried things out enough to promote really large fires,” says Park Williams, a research scientist at the Lamont-Doherty Earth Observatory at Columbia University.

In other words, the weeks of heat that baked the West in July and August were enough to wipe away some of the fire-dampening effect of the winter storms.

“The last 60 to 90 days have been exceptionally warm and dry, the perfect recipe for drying out fuels (the one ingredient besides ignitions you need for fire in these systems),” said John Abatzoglou, a professor of geography at the University of Idaho, in an email. “I was running a few numbers this morning, and the last 60 days have been record warm from Spokane, Washington, to Medford, Oregon; both Seattle and Missoula earlier this summer set records for the longest number of days without measurable rain.” […]

“Since the 1980s, we’ve only burnt about 10 percent of the western U.S. forests. And that number to me means that there’s still a whole lot more to burn,” Williams said. He estimated that it would take another several decades for that excess century of fuel to burn out of the American woods. And in the meantime, the planet will only get hotter.

“According to climate models, by the end of this century, the western United States is still projected to warm by about another 3.5 degrees Celsius,” he told me. “And when we remember that the relationship between temperature and fire is exponential … we’re really talking about a very different western United States in 50 years.” [more]

Has Climate Change Intensified 2017’s Western Wildfires?