History indicates that there will be a dangerous increase in wildfires as a result of a warming climate, warns a University of Wyoming study that will be published this week in the Proceedings of the National Academy of Sciences. Over the past 2,000 years, forest areas have seen more outbreaks of wildfires during times when there was even a slight increase in temperature.

"What our research shows is that even modest regional warming trends, like we are currently experiencing, can cause exceptionally large areas in the Rockies to be burned by wildfires," said John Calder, a Ph.D. candidate at the University of Wyoming Department of Geology and Geophysics, who led the study.

Researchers looked at charcoal deposits in 12 lakes around the Mount Zirkel Wilderness of northern Colorado, and determined that wildfires burned significant portions of that area during a documented rise in temperatures in North America that started about 1,000 years ago, during the Medieval Warm Period.

"When we look back in time, we only see evidence of large areas burning one time in the last 2,000 years," Calder said. "This suggests that large wildfires of the magnitude we have recently seen used to be very infrequent."

A U.S. Forest Service report released last month indicated that fire seasons have grown longer in recent years, as the wildfires have grown in frequency, size and severity. In Arkansas, foresters Sunday raised the alert level for wildfires, warning that the humidity is expected to drop while certain areas become unusually windy, reported the Associated Press

In the University of Wyoming study, researchers noted that the Rocky Mountain region may be more susceptible to wildfires -- the climate there has warmed about 1.25 degrees over the last 20th century. If the warming trend continues, the fires in recent years may become more extensive and catastrophic.

"The large increase in the number of sites burned by fires (during the MWP) highlights the risk that large portions of individual landscapes may burn as climates continue to warm today," the University of Wyoming researchers wrote.