Researchers write on February 10 in Nature Communications that a study of satellite data reveals “hot lightning,” or strikes that channel electrical energy for a lengthy period of time, may be more likely to ignite landscapes than more fleeting flashes. The most explosive of these Promethean bolts could grow by 10% with every degree Celsius of warming, increasing their flash rate to around four times per second by 2090 from over three times per second in 2011.
Scientist Francisco Javier Pérez-Invernón of the Institute of Astrophysics of Andalusia in Granada, Spain, cautions that this is risky. “There will be a higher chance of wildfires started by lightning.”
Lightning is the natural phenomenon that causes the most fires out of all others. Flashes that land in areas with little to no rain, or “dry lightning,” are particularly potent fire starters. Some of the most destructive wildfires in recent years, like the California fires of 2020, were started by these bolts.
Yet, factors other than dry conditions can affect a blast’s capacity to start a fire. The longest-lasting type of hot lightning, “long continuing current lightning,” has been seen in the wild and in laboratory trials to be particularly flammable. More than 40 milliseconds of current are channeled by these blows.
Some last longer than a third of a second, which is how long a human eye blinks on average.
According to Pérez-Invernón, “this sort of lightning can transfer a significant amount of electrical discharge from clouds to the earth or to vegetation. The ability of hot lightning to start a fire is comparable to lighting a candle; the longer a wick or piece of vegetation is exposed to incendiary energy, the simpler it is to start a fire.
According to earlier studies, lightning may become more frequent due to climate change (SN: 11/13/14). Little is known, however, about the potential evolution of hot lightning and its capacity to start wildfires.
Using data on lightning gathered by a weather satellite and information on wildfires from 1992 to 2018, Pérez-Invernón and his colleagues investigated the connection between hot lightning and American wildfires.
The study discovered that up to 90 percent of the approximately 5,600 fires included in the investigation could have been caused by long-continuing-current lightning. The researchers concluded that bursts of hot lightning were more likely to start fires than usual bolts since less than 10% of all lightning strikes throughout the summer in the western United States have long-continuing currents.
The effects of climate change were also investigated by the researchers. In a future scenario where annual greenhouse gas emissions peak in 2080 and then start to fall, they ran computer simulations of the worldwide lightning activity from 2009 to 2011 and from 2090 to 2095.
The research team discovered that in the future, climate change may enhance updraft within thunderstorms, resulting in an increase in hot lightning strikes to roughly 4 per second globally – a 40 percent increase from 2011. When this is happening, the frequency of all cloud-to-ground strikes may rise by 28% to around 8 flashes per second.
The researchers concluded that wildfire danger will rise significantly in Southeast Asia, South America, Africa, and Australia, and will rise most dramatically in North America and Europe. This was after taking into consideration changes in precipitation, humidity, and temperature. Several arctic regions, where rainfall is anticipated to rise while hot lightning rates stay steady, may see a reduction in risk.
Earth systems expert Yang Chen of the University of California, Irvine, who was not involved in the work, believes it is important to demonstrate how risk may develop differently in various locations. However, he points out that there is a lot of uncertainty because the research relies on scarce data from polar regions. He suggests that further data might be gathered via data sources including ground-based lightning detectors. “That [area] is crucial because permafrost can release a significant amount of carbon.”
More information, according to Pérez-Invernón, will help forecast the frequency of lightning-induced wildfires, not just in polar regions but also in Africa, where fires are frequent but fire reports are scant.
Reference: Nikk Ogasa@sciencenews.org
