A form of lightning is often used to raise fires under climate change.
An analysis of satellite data suggests that “hot lightning” – that channel of electrical charge strikes over a longer period of time – is more likely to set fire to landscapes than more flashbulbs, researchers report on February 10 in The Nature of Communication. Each 1 degree Celsius of warming could stimulate a 10 percent increase in the ignition of these Promethean lightning bolts, boosting the lightning rate to nearly four times per second by 2090 — up from nearly three times in 2011.
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It is dangerous, warns Francisco Javier Pérez-Invernón, a physicist at the Institute of Astrophysics of Andalusia in Granada, Spain. There will be more danger of wildfires.
Of all the forces of nature, the lightning flashes the most. Lightning that strikes between little or no rain — such as dry lightning — is known to be particularly effective as a fire. These lightning strikes have caused some of the most destructive wildfires in recent years, such as the 2020 California wildfires.SN: 12/21/20).
But more than dry things can affect the ability of a flame to spark. Field observations and laboratory experiments have suggested that the strongest type of heat flash — “long continuous lightning current” — is perhaps the most combustible. This current channel hits more than 40 thousandths of a second. Some longer than a third of a second – the typical duration of the human eye blink.
“This type of lightning can transport a huge amount of electrical discharge from the clouds to the ground or to the grass,” says Pérez-Invernón. A lightning bolt of fire is analogous to lighting a candle; The more the string or grass is subjected to the incendiary force, the more easily it ignites.
Previous research has proposed that lightning may rise under climate change (SN: 11/13/14). But it remained less clear how hot flashes — and the ability to ignite flames — could develop.
Pérez-Invernón and colleagues examined the relationship between heat lightning and US wildfires, using weather satellite and wildfire data collected from 1992 to 2018.
A long-continued lightning current could have shocked up to 90 percent of the approximately 5,600 flashes in the analysis, the team found. Since less than 10 percent of all summer lightning strikes in the western United States last long, calculations of relative ignition rates led researchers to conclude that lightning strikes are more prone to sparking fires than typical lightning strikes.
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Researchers have also explored the impacts of climate change. Computer simulations were run of global lightning activity during 2009 to 2011 and from 2090 to 2095, under a future scenario in which annual greenhouse gas emissions peak in 2080 and then decline.
The team found that later in the season, climate change can boost the updraft inside the thunderstorm, causing lightning strikes to increase in frequency to about 4 globally per second – an increase of about 40 percent since 2011. Meanwhile, the rate of all cloud-to-ground strikes to increase to about 8 lamps per second, a 28 percent increase.
After taking into account changes in precipitation, humidity and temperature, the researchers announced that the wild fire risk will increase significantly in Asia, Southeast America, Africa, Australia, and the risk will rise most dramatically in North America and Europe. However, the risk may decrease in many polar regions, where rainfall is projected, while rates of hot flashes are expected to increase steadily.
It’s useful to show that risk can develop differently in different areas, says Earth systems scientist Yang Chen of the University of California, Irvine, who was not involved in the study. But he notes, the analysis uses sparse data from polar regions, so there is a lot of uncertainty. He says a combination of additional data from lightning detectors and other data sources could help. “What” [region is] important because a lot of carbon can be extracted from the permafrost.”
Pérez-Invernón agrees that more data will help to improve the projections of lightning-induced wildfire rates, not only in polar regions, but also in Africa, where flames are common, but fire reports are lacking.
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