Wildfire risk to worsen as warming climate increases lightning strikes, scientists warn

New study suggests thunderstorms could become more common by end of century, writes Peter Stubley

Smoke rises from a wildfire near Anchorage in Alaska during the 2019 heatwave (Getty)

Five years ago a Nasa-led team of scientists studying wildfires in Alaska made a thought-provoking discovery.

It had been a record-breaking year for fires in the region and there were increasing concerns that the climate crisis was making these outbreaks not only more common but also bigger and longer-lasting.

But what was triggering the fires in the first place? The scientists noted that most were not sparked by careless or malicious human activity but by a force of nature: lightning strikes.

The finding prompted Professor James Randerson and his team at the Earth System Science school in the University of California, Irvine, to try and predict how the weather phenomenon would be affected by the warming climate within the Arctic Circle.

Lightning is rare in higher latitudes because of the lower temperatures and humidity. So much so that when strikes were spotted within 300 miles of the North Pole in 2019, it prompted the US national weather service to issue a public information statement.

However Professor Randerson's concern is that if lightning became more common then there would be a higher risk of wildfires in northern regions, which in turn could further drive even more warming.

For example, if fires burn away grasses, mosses and shrubs covering the Arctic tundra, evergreen forests will begin to expand north and replace what is usually a snow-covered landscape.

These forests will in turn absorb solar energy, helping to warm the region even further.

More fires could also melt the permafrost that stores organic carbon which will convert to carbon dioxide and methane, potentially driving even more warming.

2015 was an exceptional fire year [in Alaska] because of a record number of fire starts. One thing that got us thinking was that lightning was responsible for the record-breaking number of fires.

Professor James Randerson

To predict the number of lightning strikes in Arctic regions, research scientist Yang Chen examined Nasa satellite data from 20 years ago in an attempt to determine the relationship between the "flash rate" and weather conditions.

The team then used United Nations climate projection models to estimate the number of lightning strikes at higher latitudes in the future.

They found lightning strikes would increase by about 100 per cent by the end of the century as a result of increases in atmospheric convection and more intense thunderstorms.

"We projected how lightning in high-latitude boreal forests and Arctic tundra regions will change across North America and Eurasia," said Mr Chen. "The size of the lightning response surprised us because expected changes at mid-latitudes are much smaller."

The team at UCI say their findings show that scientists need to start paying more attention to the frequency of Arctic lightning strikes.

Prof Randerson said he hopes the results will also help boost calls for new satellite missions that can monitor Arctic latitudes for lightning strikes and wildfires.

"This phenomenon is very sporadic, and it's very difficult to measure accurately over long time periods," said Prof Randerson.

The study was funded by the US Department of Energy's Office of Science and Next Generation Ecosystem Experiment Arctic project and NASA's Interdisciplinary Science and Carbon Monitoring System program. It also included researchers from the University of California, Berkeley; Lawrence Berkeley National Laboratory; Harvard University and Vrije Universiteit Amsterdam.