Warming Climate Means More Wildfires in Western US – NASA Scientists Say

Image: An August 2000 wildfire in Bitterroot National Forest, Montana. Credit: Alaska Forest Service/John McColgan

Wildfires are already a common occurrence in the Rocky Mountain West. And if NASA scientists are correct, a warming climate will only ramp up the frequency of wildfires in future.

Over the past 30 years, warmer and drier conditions in the Rocky Mountain West have made vegetation more flammable, which has led to an increase in wildfires, said Peter Hildebrand, director of the earth sciences directorate at NASA’s Goddard Space Flight Center, speaking at the Conference on World Affairs at the University of Colorado this week.

A new NASA wildfire model shows that these increasing fire trends are set to continue with a warming climate, Hildebrand said during the panel in Boulder.

As the earth heats up, global circulation patterns are changing and the winter storm track is being pushed further north. This results in less precipitation, higher temperatures and more evaporation in the Rocky Mountain West, Hildebrand explained.

NASA scientists project that with the effects of climate change, the frequency of fires in the West could increase between 30 and 60 percent by 2100. At the same time, the wetter Eastern part of the country is expected to experience decreased fire rates in the future.

“I want you to think a little bit of fire as a metaphor for the many things that climate change holds for us,” said Hildebrand.

In terms of adapting to increased fire activity, it’s important for people living in fire-prone areas to think about home construction, the vegetation around their homes and the location of homes, he said.

To build their wildfire model, the scientists used satellite measurements of vegetation density, temperature, precipitation, lightning and fire activity over recent decades and plugged them into a computer model to estimate climate and fire conditions dating back to the year 850. They combined these estimates with land-use and population reconstructions. The scientists compared this computer modeled data to charcoal layers harvested from lake core sediments around the world, dating back 2,000 years, and found a good correlation between the data.

At the same time, in a 2010 paper the scientists note that the model is not perfect because “highly incomplete” information on fire-related human activities makes it difficult to gauge the role humans played, globally, in igniting and suppressing fires, especially during the Industrial Period.

The wildfire model identifies three key eras in global fire history. Before the industrial era, precipitation levels largely dictated fire levels around the world, according to the scientists.

“By and large humans were not very much affecting climate before the industrial revolution,” said Hildebrand.

From the industrial age onward, rapid population growth led to an increase in human-caused fire and by 1900 the number of fires around the world had increased to about 20 percent higher than pre-industrial levels, said Hildebrand.

After 1900 there was a significant reduction in wildfire because of improved firefighting technologies, he said.

And while humans have been responsible for starting the majority of fires over the past century, and for successfully putting them out, by 2050 the model predicts that warmer temperatures will play a key role in dictating fire activity around the world.

“These results suggest a possibility that in the future climate will play a considerably stronger role in driving global fire trends, outweighing direct human influence on fire (both ignition and suppression), a reversal from the situation during the last two centuries,” the scientists write.

“Our projections show that our rising temperatures — this time driven by humans — are on the verge of reasserting control over the world’s fires,” said study author Olga Pechony in a NASA news report.

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