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Colorado’s Marshall fire: Climate change and growing population led to disaster in Boulder County, scientists say

The fire struck grassland that has been drying out since summer

A man walks amid burned homes in the Coal Creek Ranch subdivision in the aftermath of the Marshall Fire in Louisville on Dec. 31, 2021.
A man walks amid burned homes in the Coal Creek Ranch subdivision in the aftermath of the Marshall Fire in Louisville on Dec. 31, 2021.
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Becky Bolinger and the team at the Colorado Climate Center have kept watch over the dry and warm conditions that have blanketed the Front Range since the summer, knowing that they provided the perfect recipe for a wildfire.

For them, it was a matter of when and where a fire would spark – not if one would happen, said Bolinger, the assistant state climatologist at the center at the Colorado State University.

Still, Bolinger and other scientists who spoke to The Denver Post, were surprised by the location of the wind-swept Marshall fire that rapidly spread through Boulder County on Thursday. Instead of mountain forests, the flames spread through suburban neighborhoods and forced tens of thousands of Coloradans from their homes as the state’s burgeoning population collided with climate change.

“I have thought it won’t be long before we start experiencing fires like California where flames chase people out of their neighborhoods,” Bolinger said. “I didn’t expect that would happen in December.”

High winds are common in Colorado and even brush fires are known to happen in Boulder in December, although they aren’t common. The Marshall fire, which spread over 6,000 acres in a matter of hours, is unique in its intensity and how it struck grassland — now filled with thousands of homes — that have been drying out for months, climate scientists said.

The grass grew tall — remnants of a wet spring — and began drying out in the summer amid a decades-long drought. Making matters worse, the period between June and December has been the warmest period on record and among one of the driest periods for the Denver metro area since the early 1960s, said Jennifer Balch, a fire scientist and director of the Earth Lab at CU Boulder.

“The drier the kindling is, the more easily that fire is going to spread,” added Bolinger

A warming climate laid the foundation for wildfires to happen year-round instead of just in the summer and that needs to be taken into consideration as more homes are built, the scientists said.

“Climate change is definitely a part of this story in that fire seasons are longer,” Balch said. “We don’t have a season any longer. We are now looking at year-long fires.”

The Marshall fire has also made scientists realize that the wildland-urban interface, where developments meet natural land, is larger than they knew, Balch said.

“There’s now much more development for a fire to affect,” said Bob Henson, a meteorologist and writer for Yale Climate Connections. “Many of the areas hit were grassland 40 years ago.”

The snow hitting the Front Range on Friday and Saturday will help, but if the days go back to being warm, dry and windy after the storm that relief may not last, Bolinger said.

“The memory of this snow could be short and it could evaporate and leave the ground quickly and then we could be at risk again,” she said.