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Fire weather seasons across the globe getting longer

Posted date: July 14, 2015

Wildfire trends from 1979-2013 show unusually long fire seasons occur more frequently across much of the globe

FORT COLLINS, Colo., July 14, 2015 – Scientists found trends in fire weather seasons across the globe have increased by nearly 20 percent and the global burnable area doubled (nearly 110 percent) over the past 35 years.

Scientists from the USDA-Forest Service, South Dakota State University, the Desert Research Institute and the University of Tasmania, Australia conducted the study, Climate-induced variations in global wildfire danger from 1979 to 2013, published in the international journal Nature Communications.

Wildfire activity is driven by three key factors; fuels, sources of ignition, and weather (temperature, relative humidity, precipitation, and wind speed). Of the three factors, weather is the most variable and largest driver of regional burned area.

“So we separated weather from the other driving factors in order to isolate the impacts of climate change on wildland fire potential,” said lead scientist Matt Jolly of the USFS Rocky Mountain Research Station’s Fire Science Lab.

All continents with the exception of Australia and most vegetation types except boreal forests showed significant increases in the fire weather season length. Some areas, such as the Western and Southeastern United States, Alaska, tropical and sub-tropical South America and Eastern Africa and large parts of Eurasia show a steady lengthening of the fire season from 1979-2013. “Although, Australia and boreal forests showed no significant fire season length trends, we identified regional increases in the frequency of unusually long fire seasons in those regions since the mid-1990s, said Jolly. Essentially, while fire seasons aren’t getting consistently longer everywhere, unusually long fire seasons have been more frequent across much of the globe, even in areas such as Australia and the global boreal forests where significant long-term trends were absent.“

Notably, the methodology used in this study to explore and explain complex observed variations in fire activity is relevant when applied to any given geographic area whether it is local, regional, national or international. Understanding what is driving these trends can help managers toward mitigating increased wildfire potential, which can have pronounced global socio-economic, ecological and climate system impacts.

NASA Headquarters under the Terrestrial Ecology Program of the NASA Science Mission Directorate’s Earth Science division supported this work. NASA provided additional funding through an applied wildland fire sciences award.

To download a copy of Climate-induced variations in global wildfire danger from 1979 to 2013 go to

Map depicting global patterns of fire weather season length changes from 1979-2013
Map depicting global patterns of fire weather season length changes from 1979-2013

In the image above a. shows areas with significant trends in fire weather season length from 1979 to 2013. b. shows regions that have experienced changes in the frequency of long fire weather seasons (41s above historical mean) during the second half of the study period (1996–2013) compared with the number of events observed during the first half (1979–1996). Areas with little or no burnable vegetation are shown in grey (NB) and NC indicates areas with no significant change. Reds indicate areas where fire weather seasons have lengthened or long fire weather seasons have become more frequent. Blues indicate areas where fire weather seasons have shortened or long fire weather seasons have become less frequent.

The Rocky Mountain Research Station (RMRS) is one of seven units within the U.S. Forest Service Research and Development. RMRS maintains 14 field laboratories throughout a 12-state territory encompassing parts of the Great Basin, Southwest, Rocky Mountains, and the Great Plains. RMRS also administers and conducts research on 14 experimental forests, ranges and watersheds and maintains long-term research databases for these areas. While anchored in the geography of the West our research is global in scale. To find out more about the RMRS go to You can also follow us on Twitter at




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National Strategic Program Areas: 
Wildland Fire and Fuels
National Priority Research Areas: 
Climate Change
RMRS Science Program Areas: 
Fire, Fuel and Smoke
RMRS Strategic Priorities: 
Disturbance Ecology; Fire Sciences
Cass Cairns
Public Affairs Specialist