(a) Changes in the global mean fire weather season length from 1979 to 2013 with 95 percent confidence limits between ensemble members (shaded area). (b) Total global annual area affected by long fire weather seasons (>1σ of historical mean). (c) Inter-annual variations in the standard anomalies of global mean rain-free days. Global mean rain-free days accounted for 49.7 percent of the variation in global fire weather season length and 33.8 percent of the variation in global long fire weather season affected area. Graph: Jolly, et al., 2015 / Nature Communications

By David Erickson
19 July 2015

MISSOULA (Independent Record) – The length of wildfire seasons across the globe and the burnable areas of Earth’s surface have drastically increased in the past three decades due to climate change, according to a groundbreaking new study supported by years of research from the U.S. Forest Service's Missoula Fire Sciences Laboratory.

In a paper published Tuesday in the international journal Nature Communications, a team of researchers concluded that from 1979 to 2013, fire weather seasons have lengthened across 18.39 million square miles of Earth’s vegetated surface, resulting in an 18.7 percent increase in the global average fire season length. The global burnable area affected by long fire seasons has doubled in that time, and from 1996 until 2013 there has been a 53.4 percent increase in the frequency of long fire seasons.

One of the study’s lead authors, Matt Jolly, is a Fire Sciences Lab ecologist at the Rocky Mountain Research Station in Missoula. Inside the cavernous facility, scientists conduct cutting-edge research on wildland fires using wind tunnels and massive burn chambers. Jolly spent four years of his life immersed in computer models and digging through historical climate and fire data to assist the study. […]

What we wanted is a metric that we could apply equally across the whole globe,” Jolly explained. “The change we found comes in two forms: steady long-term increase in fire season length as limited by weather and an increase in the frequency of extremely long fire seasons.”

The researchers found there are long-term steady increases in fire seasons in places that normally don’t see many fires, like the southeastern U.S., especially the coastal plains of Florida.

“That area has seen some extremely large fires in the last decade, even though that doesn’t get a lot of press,” Jolly said.

All continents except Australia and most vegetation types except boreal forests showed significant increases in the fire weather season length, however, those excepted areas are seeing unusually long fire seasons as well. […]

Every year, an estimated 864 million acres of land burn in wildfires across the globe, and carbon dioxide emissions from fires can exceed 50 percent of fossil fuel combustion emissions. In the last decade, wildfire suppression costs on U.S. federal lands exceeded $1.7 billion, and Canada spent an additional $1 billion. When preparedness and suppression costs are combined with economic losses, the total costs of fires are substantially higher. In 2005, for example, Australia spent $9.4 billion combating fires, or 1.3 percent of the country's entire annual economic output. […]

Steve Running, a regents professor of ecology at the University of Montana's College of Forestry and Conservation, said he was impressed by the thoroughness of the study. […]

“In my public talks, I always make a point of saying that climate change isn't a future projection, it actually started around 1980," Running explained. "It is interesting that this data set started in 1979. As I look over the past century, I can show three or four data sets that were stable until 1980, and then there is a pretty clear trend of data sets that started in a different trajectory. We saw a clear climate trend developing." [more]

Study finds climate change is increasing length of wildfire seasons across globe


ABSTRACT: Climate strongly influences global wildfire activity, and recent wildfire surges may signal fire weather-induced pyrogeographic shifts. Here we use three daily global climate data sets and three fire danger indices to develop a simple annual metric of fire weather season length, and map spatio-temporal trends from 1979 to 2013. We show that fire weather seasons have lengthened across 29.6 million km2 (25.3%) of the Earth’s vegetated surface, resulting in an 18.7% increase in global mean fire weather season length. We also show a doubling (108.1% increase) of global burnable area affected by long fire weather seasons (>1.0 σ above the historical mean) and an increased global frequency of long fire weather seasons across 62.4 million km2 (53.4%) during the second half of the study period. If these fire weather changes are coupled with ignition sources and available fuel, they could markedly impact global ecosystems, societies, economies and climate.

Climate-induced variations in global wildfire danger from 1979 to 2013

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