The rare December blaze that tore through Boulder County, Colorado, at frightening speed this week may not be that unusual in the future, wildfire experts warn, as climate change sets the stage for more.
Wildfires do not historically happen during the winter, particularly in areas like Boulder County, where the ground is normally moist from snow.
But in recent months, Colorado has experienced a severe drought. From July 1 through Dec. 29, Denver recorded its lowest amount of precipitation by over an inch, with snowfall at record low levels, too. Meanwhile, Boulder, which typically gets about 30 inches of snow from September to December, got just 1 inch in that period leading up to the day of the fire.
Combine that with an unseasonably warm fall, and the ground had significantly less moisture in it than it normally would — creating perfect conditions for a fire to flourish.
“Everything is kind of crispy,” said Keith Musselman, a snow hydrologist and assistant research professor at the University of Colorado Boulder. “In addition to the extreme drought, just 1- or 2-degree warmer days can really dry out the landscape quite a bit more, so everything is that much drier and flammable.”
Officials say wind gusts up to 105 mph fanned the flames, rapidly destroying 500 to 1,000 homes and giving residents barely any time to evacuate.
While gusts of that magnitude are somewhat out of the ordinary this time of year, they cannot be directly tied to climate change, said Daniel Swain, a climate scientist at UCLA and the nonprofit Nature Conservancy.
However, he said, climate change was definitely the reason the ground was primed for the wind-whipped fire to take off, and wildfire seasons could lengthen similarly in other areas.
“Climate change is clearly making the pre-conditions for wildfires worse across most fire-prone regions of the world,” he said.
In addition to the time of year, Colorado’s fire stood out for another reason, said Philip Higuera, a professor of fire ecology at the University of Montana. Very few burn as many structures.
“Unfortunately, this illustrates one of the worst-case scenarios,” he said of the fact that the blaze burned through densely populated neighborhoods. “These are these high-wind events under these extremely dry conditions, and you’re basically crossing your fingers and hoping there isn’t a human-caused ignition in the wrong place.”
Addressing the problem
The solution, the experts say, is two-pronged: Attack climate change through actions and discussions within communities and households in the long term and, in the short term, do not assume that certain areas are immune from fires.
“We as a society need to recognize that wherever we’re living in the West with vegetation is a fire-prone environment,” Higuera said. “This can happen anywhere.”
That might mean changing how homes are built or reinforced to make them more fire-proof or changing infrastructure so power lines are buried or shut off during high-wind events, he said.
Officials initially suspected that a downed power line caused the blaze Thursday in Colorado but said later that the investigation had revealed that there had not been any. They said they were still investigating.
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 don’t think winter is ever going to be peak fire season in the West,” he said. “But it used to be a fire non-season, and I really don’t think that’s the case anymore.”
