Some areas are now seeing two more months of fire weather each year than they were in the 1970s. (Photo: Amanda Bronstad/ALM)
As the LA wildfires continue to rage, many are asking how they started. One of the culprits is likely climate change.
The contiguous United States is 2.6 degrees Fahrenheit warmer today than it was in 1970, according to an analysis by Climate Central. That rise coincides with longer, drier fire seasons in many places.
“Fire weather”— when meteorological conditions are right for wildfires — depends on three things: hotter temperatures, low relative humidity and wind:
- Hotter temperatures make it easier for fires to ignite, and warmer nighttime temperatures in particular decrease the overnight relative humidity that firefighters often rely on to gain control of wildfires.
- When relative humidity levels are consistently low, moisture is pulled from vegetation, creating dry kindling.
- Adding wind to the mix — like the Santa Anas blowing through California — supplies oxygen to the fire so it can burn more rapidly and increases evaporation, further drying out the land. Wind can also carry embers, helping the fire spread.
Between these hot and dry periods, California and other areas are also seeing major storm and flooding events, creating what a new report calls “hydroclimate whiplash” — fast swings between very wet and very dry weather patterns.
A warmer atmosphere is able to hold water vapor for longer before raining or snowing, deepening droughts, intensifying storms — and creating greater wildfire risk.
“Things like atmospheric rivers deliver a lot of moisture, but that doesn’t necessarily help,” said Kaitlyn Trudeau, senior research associate for climate science with Climate Central, in a press briefing hosted by Covering Climate Now on Tuesday. “All that rain really promotes a lot more vegetation, then that vegetation dries out and you have more kindling for wildfires.”
The report’s authors found hydroclimate whiplash has increased by up to 66% since the 1950s, and they expect it to nearly double in coming years as warming increases.
“It’s really all connected,” Trudeau said. “It’s the warming. It’s the drying. It’s the increase in extremes.”
Rachael Myrow, senior editor at KQED’s Silicon Valley news desk, noted in the press briefing that many people are seeking to blame utilities, politicians and others for starting the fires. While their actions may have played a role in the current wildfires, “it’s a collection of bad decisions that have led up to this moment,” she said.
As climate change continues to create larger-scale natural disasters, it’s going to require us to move toward long-term prevention and solutions. “There’s been a shift in more recent years, as we see more intense wildfires and hurricanes, and that’s requiring us to grasp that we need to respond on a different level,” she said.
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