This analysis uncovered a striking pattern, Hu said.
"There is a dramatic, nonlinear relationship between climate conditions and tundra fires, and what one may call a tipping point," he said. Once the temperature rises above a mean threshold of 10 degrees Celsius (50 degrees Fahrenheit) in the June-through-September time period, he said, "the tundra is just going to burn more frequently."
For the past 60 years, annual mean temperatures during this warm season have fluctuated between about 6 and 9 degrees Celsius (42.8 to 48.2 degrees Fahrenheit), with temperatures trending upward since 1995. In 2007, the year of the historic fire, the mean temperature was a record 11.1 degrees Celsius, while precipitation and soil moisture dipped to an all-time low.
Higher precipitation, if it occurs, could dampen the effects of higher temperatures, but only to a limited extent, said Philip Higuera, a professor of forest ecology and biogeosciences at the University of Idaho and a co-author on the study.
"As temperature rises, so too does evaporation," he said. "So even if future precipitation increases, it's likely that increased evaporation will result in overall lower moisture availability. This affects plants, but it also makes dead vegetation more flammable and fire prone."
|Contact: Diana Yates|
University of Illinois at Urbana-Champaign