Global warming | Lightning will strike more often in Quebec

Climate change is expected to increase lightning episodes in boreal forests by 20% by the end of the century, according to a new British study. However, lightning ignites half of the fires in the country.

Scientists disagree on the impact of climate change in the tropics, but at higher latitudes there is consensus.

“In large, unmanaged forests in the North, there is expected to be an 11% to 31% increase in lightning frequency for every one degree increase in temperature,” says Matthew Jones of the University of California. East Anglia. He is the lead author of the study linking lightning and global warming published Thursday in the journal Nature Geoscience. “Models agree on this, although they differ for the tropics, where most lightning occurs. »

These extratropical forests, like the boreal forest, are located between 50 and 60 degrees latitude, north of Chibougamau in Quebec.

As the mercury will rise faster in the Far North than at the equator, does this mean that the frequency of lightning will increase more quickly in the boreal forest? “The average 20% increase in lightning frequency is calculated relative to the average increase in global temperature,” confirms Mr. Jones.

Winter and clouds

Several uncertainties remain. Mr. Jones cites, for example, the possibility that lightning could become more common at higher latitudes: a degree of temperature increase would increase the frequency of lightning by more than 20% at 60 degrees latitude, and by less than 20%. at 45 degrees latitude.

Other points that remain to be studied are the seasonality of lightning and its altitude. About half of lightning travels from cloud to cloud, so does not cause fires. And lightning can only cause fires when conditions are right, generally not in winter when there is a cover of snow on the ground.

Preliminary data shows that the proportion of lightning that travels from cloud to cloud, to the ground, is preserved with the increase in frequency caused by climate change. But when it comes to seasonality, there is a lack of data.

Since the planet has warmed by just over 1.1°C compared to the pre-industrial era, does this mean that there are already 20% more lightning strikes in extratropical forests?

“There is a serious lack of data to reach this conclusion,” says Mr. Jones. Fortunately, there has been a North American database for around fifteen years which was extended to the whole world a few years ago. Within 10, 15 years, we will really be able to have real correlations between temperature and lightning. And also for other uncertainties. »

We’ve seen record wildfires in Canada this year, with 18.4 million hectares burned before the start of November. Previously, the record — historical statistics dating back to 1980 — was 7.5 million hectares, in 1989, according to the National Wildfire Database.

If 45% of forest fires in Canada are caused by lightning, the latter is responsible for 81% of the area burned, according to Natural Resources Canada.