How climate change enabled Colorado to a rare wildfire in December

The rare December flames tearing through Boulder County, Colorado, at frightening speeds this week, may not be so unusual in the future, warns wildfire experts as climate change sets the stage for more.

Wildfires do not historically occur in the winter, especially in areas like Boulder County, where the ground is usually moist from snow.

But in recent months, Colorado has experienced a severe drought. From July 1 to December 29, 2021, Denver recordreduced its lowest amount of precipitation by over an inch, with snowfall at record low levels as well. Meanwhile, Boulder, as typical ser about 30 inches of snow between September and December, received only one inch in the period up to the day of the fire.

Combine that with an eerily hot autumn, and the soil had significantly less moisture in it than it normally would – creating perfect conditions for a fire to flourish.

“Everything is a little brittle,” said Keith Musselman, a snow hydrologist and assistant research professor at the University of Colorado Boulder. “In addition to the extreme drought, just one or two degree warmer days can really dry out the landscape a lot more, so everything is so much drier and flammable.”

Officials say gusts of up to 105 mph blew up the flames, quickly destroyed between 500 and 1,000 homes and left residents with little time to evacuate.

While gusts of magnitude of that magnitude are something out of the ordinary for this time of year, they may not be directly linked to climate change, said Daniel Swain, a climate researcher at the University of California Los Angeles and nonprofit Nature Conservancy.

But, he said, climate change was definitely the reason the earth was ready for the wind-whipped fire to ease, and other areas may experience similar extensions of their wildfire seasons.

“Climate change is clearly making the conditions for wildfires worse in most fire-prone regions of the world,” he said.

In addition to the time of year in which it occurred, the Colorado fire stood out for another reason, said Philip Higuera, professor of fire ecology at the University of Montana. Very few burn as many structures as this one.

“Unfortunately, this illustrates one of the worst-case scenarios,” he said of the fact that the fire burned through densely populated neighborhoods. “These are these powerful wind events under these extremely dry conditions, and you are basically crossing your fingers and hoping that there is not a man-made ignition in the wrong place.”

Solving the problem

The solution, experts say, is two-pronged: to tackle climate change through actions and discussions in communities and households in the long run, and in the short run without assuming that a particular area is immune to fires.

“We as a society need to recognize that wherever we live in the West with vegetation, it is a flammable environment,” Higuera said. “This can happen anywhere.”

That could mean changing the way homes are built or reinforced to make them more fireproof, or changing infrastructure so that power lines are buried or shut off during strong winds, he said.

Officials initially suspected a broken power line was the cause of Thursday’s fire in Colorado, but later said the investigation showed there had been none. They said they continued to investigate the cause.

While fires are likely to become more common year-round, Swain said winter still would not be a time of high fire activity.

“I still do not think winter will ever be the peak season for fire in the West,” he said. “But it used to be a brand out of season, and I really don’t think that’s the case anymore.”

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