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The drought-plagued western U.S. has had more than its share of fires this year – but this may not be the last year that the nation sees so many wildfires gone wild.

A Yale University professor looking back over the last 3,000 years at charcoal accumulations in lake bottoms and tree rings found that such warm temperatures and dry conditions as the West is experiencing typically produce more fires.

And the warming effects of climate change will likely bring even more fires, Jennifer Marlon, an associate research scientist at the Yale School of Forestry & Environmental Studies, told Insurance Journal this week.

Marlon and her colleagues in 2012 issued a study titled, “Long-term perspective on wildfires in the western USA,” which shows a relationship between drought, temperatures and fire frequency.

Her wildfire message to those in the West based on current warming trends and the recent spate of wildfires: “I don’t see much relief in the near future.”

In the wake of the Industrial Revolution, the report shows a “fire deficit” occurred in the late 20^th Century, which the authors attribute to agriculture, logging, firefighting and the construction of roads and infrastructure that divided large forests.

A “fire deficit” sounds positive. But what it means simply is that there’s a lot of fuel to burn, which is just what happened over the past year following three relatively calm years with lower wildfire claims despite persistent drought.

A report in October forecasts claims from two Northern California wildfires in September will exceed $1 billion.

The Valley Fire destroyed 1,958 homes and other structures, with economic losses expected to exceed $1.5 billion and insured losses estimated at more than $925 million, while the Butte Fire caused estimated economic losses of $450 million and insured losses expected to be above $225 million, according to the report.

Risk experts believe the fires are changing the way insurers look at underwriting the risk on rural California homes, and the California Department of Insurance has had reports from consumers in the burned areas that it’s difficult to find insurance.

Marlon’s study shows biomass burning in the western United States has remained in “dynamic equilibrium with climate” at least since 500 to the 1800.

“Burning generally increased when temperatures and drought area increased, and decreased when temperatures and drought declined,” the study says.

However, human activities had an impact after the late 1800s, according to the study.

“The divergence in fire and climate since the mid 1800s CE has created a fire deficit in the West that is jointly attributable to human activities and climate change and unsustainable given the current trajectory of climate change,” the report states.

Among these human activities was “grazing from millions of cattle and sheep,” Marlon said.

“They just ate the fuels basically,” she added.

Logging helped by removing more fuels, and trails and roads that were being built dissected the landscape and separated vegetation, preventing many of the massive fires that historically occur, she said.

But there’s still plenty to burn – note California’s recent wildfires – and Marlon believes the ongoing changes in the climate will continue to result in more fires.

She bases this on her 2012 study, which she said clearly shows that droughts over the last few thousand years have resulted in more fires.

“We feel pretty confident that climate is having a really strong control over fire,” Marlon said.

When looking at trends over decades or centuries, what Marlon found is that temperature played a bigger role in fire seasons than originally believed.

Temperatures can impact evaporation of water from the air and they can affect length of a fire season and when the snowpack melts, she said.

“I think a lot of people underestimate the importance of warming temperatures alone,” she said. “We’re seeing more days with extreme heat.”

Looking at the last few years since her study was published, she expects that rising temperatures and dry conditions are going to make things worse.

“We see the clear trends in the year-to-year area burned,” she said. “It’s going up and it’s going up clearly, yet we have forest left to burn, so I don’t see things slowing down in the next 10 years or so.”

Past columns:

• Watchdog Says Corporations Say One Thing, Do Another on Climate Change
• Sierra Club Dragging State Farm into Climate Change Battle
• Chilling Out Will Be Answer to Climate Change, Scientist Says
• Is Climate Change Now Its Own Industry?
• Report Sees Major Food Shortage as Climate Change Danger

Topics Catastrophe Natural Disasters California Wildfire Climate Change