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Study Explores The Reasons Behind Western Wildfires

Associated Press
Associated Press

Firefighters battle the Blue Cut Fire in the Cajon Pass near San Bernardino, Calif., August 2016.

A new study coming out of Columbia University explores the relationship between climate change and wildfires in the West.

Park Williams is the lead author of the study and a Bioclimatologist at Columbia University’s Lamont-Doherty Earth Observatory.

“We wanted to know what is the case that can be made about the connection between human-caused climate change and wildfire in California," Williams told KNPR's State of Nevada, "California is probably the center of the biggest debate about this issue with some people saying that climate change has caused all of the increases we’ve seen in California but not knowing necessarily how and other saying climate change isn’t responsible and that’s all due mismanagement of forests or changes in human population. We wanted to get to the bottom of the answer to that question.”

Williams would not use the word "decisive" when talking about the link between fires and climate change. Instead, he called it an "extremely probably link," adding "there is a very, very high chance that this link we detected is real."

The link researchers detected compared fire records, climate variables and climate models. 

Williams said there is a strong relationship between fire activity and one particular climate variable.

“There has been a big increase in forest fires, especially during the summertime. And the climate variable that dictates how much forest fire there is in any given year is temperature and more precisely it is the evaporative demand of the atmosphere. The aridity of the atmosphere.”

Williams explained that hotter temperatures draw more moisture from vegetation and the soil. So, as temperatures of the air have increased, the atmosphere has become more thirsty, plants have become drier and there have been more forest fires.

“The amount of forest fire that has increased over the last 50 years is just about exactly what you would expect based on the statistical relationship that we’ve seen between forest fire and temperature,” he said.

However, Williams pointed out there are a lot of factors that go into why a forest burns, including nearly a century of poor forest management. When fires begin, humans tend to put them out, which means areas of the forest are loaded with fuel.

“Now, as we warm the air and dry things out, there is more to burn during the big hot years,” he said.

But the year-to-year data on temperature and forest fires hasn't changed over 50 years. 

“What that tells us is that the dominate driver is very likely the climate change and underlying that is the amount of forest that there is to burn,” he said.

Willaims believes allowing more controlled burns in specific areas could help minimize the risk of large fires.

“I do believe we need to accept that in the West there are going to be increases in fire activity no matter what in the next few decades because it’s warming but there are some places where we can at least guide that process,” he said.

But, he said people don't like controlled burns because of the smoke and the risk of it getting out of control. Williams said the public has become more comfortable with the chance of a large wildfire than being at fault for problems when a controlled burn gets out of control.

Key points from the study:

  • Annual burned area in California increased five-fold during 1972-2018, mainly due to summer forest fires.
  • Anthropogenic or human-caused warming very likely increased summer forest fires by drying fuels. This trend is likely to continue.
  • Large fall fires are likely to become increasingly frequent with continue warming and possibly gradual declines in fall precipitation.

Park Williams, Bioclimatologist, Columbia University's Lamont-Doherty Earth Observatory



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Since June 2015, Fred has been a producer at KNPR's State of Nevada.