A new NASA-funded study found that extreme lightning storms caused by climate change were the main driver of recent massive fire years in Alaska and Canada.
The study – published today in Nature Climate Change – showed that increased lightning associated with climate change is causing more fire ignitions, and that these storms are likely to move farther north with climate warming, potentially altering Northern landscapes.
“These trends are likely to continue,” said WHRC scientist and study co-author Brendan Rogers. “We expect an increasing number of thunderstorms, and hence fires, across the high latitudes in the coming decades as a result of climate change. This is confirmed in the study by different climate model outputs.”
The team, which was led by Sander Veraverbeke of Vrije Universiteit Amsterdam, analyzed satellite images from NASA’s Moderate-Resolution Imaging Spectroradiometer (MODIS) instruments on NASA’s Terra and Aqua satellites and data from ground-based lightning networks to study the cause of the fires, whose numbers have been increasing in recent years. Record numbers of fires occurred in the Canadian Northwest Territories in 2014 and in Alaska in 2015. They found increases of between two and five percent a year in the number of lightning-ignited fires since 1975.
Veraverbeke said that while the drivers of large fire years in the northern high latitudes are still poorly understood, the observed trends are consistent with climate change.
“We found that it is not just a matter of more burning with higher temperatures. The reality is more complex: higher temperatures do also invoke more thunderstorms. Lightning from these thunderstorms is what has been igniting many more fires in these recent extreme events,” Veraverbeke said.
Study co-author Charles Miller of NASA’s Jet Propulsion Laboratory in Pasadena, California, said that while data from the lightning networks were critical to this study, it is challenging to use these data for trend detection because of continuing network upgrades. “A spaceborne sensor that provides lightning data that can be linked with fire dynamics would be a major step forward,” he said.
The researchers found that the fires are creeping farther north, near the transition from boreal forests to Arctic tundra. “In these high-latitude ecosystems, permafrost soils store large amounts of carbon that become vulnerable after fires pass through,” said co-author James Randerson of the University of California, Irvine. “Exposed mineral soils after tundra fires also provide favorable seedbeds for trees migrating north under a warmer climate.”
“Taken together, we discovered a complex feedback loop between climate, lightning, fires, carbon and forests that may quickly alter northern landscapes,” Veraverbeke concluded. “A better understanding of these relationships is critical to better predict future influences from climate on fires, and from fires on climate.”
WHRC is an independent research institute where scientists investigate the causes and effects of climate change to identify and implement opportunities for conservation, restoration and economic development around the globe.