North America is seeing an "emerging phenomenon" in which night wildfires rage during periods of drought, a study reveals.
Usually, the conditions that kindle huge wildfires are extreme only in the daytime. The cool conditions that come with the night usually relieve these conditions. However a University of Alberta researcher has now found that this isn't the case, and during periods of drought wildfires are still a risk during the night. The study's results were published in Nature.
"I think it is important to bring this emerging phenomenon to the public to let them know that the night might not save us," Kaiwei Luo, a Ph.D. student in the Canadian college's Faculty of Agricultural, Life & Environmental Sciences, who led the study, said in a findings summary.
To reach these findings, Luo oversaw a team that analyzed 23,557 North American fires between 2017 and 2020 using satellite and terrestrial data to find out more about their burn cycle.
The researchers found that fires were thriving at night because of an increase in accumulated fuel dryness in the environment. Some of the overnight fires that started this way lasted for weeks, the study said.
"Although warming is weakening the climatological barrier to night-time fires, we found that the main driver of recent [overnight burning events] in large fires was the accumulated fuel dryness and availability (that is, drought conditions), which tended to lead to consecutive [overnight burning events, or OBE] in a single wildfire for several days and even weeks," the authors wrote in the study.
"Critically, we show that daytime drought indicators can predict whether an OBE will occur the following night, which could facilitate early detection and management of night-time fires," the authors continued. "We also observed increases in fire weather conditions conducive to OBEs over recent decades, suggesting an accelerated disruption of the diurnal fire cycle."
Scientists already know that the risk of wildfires is increasing as the climate gets warmer, particularly in the American West. California is the state that suffers the most from wildfires, and until recently it was subject to prolonged drought conditions.
Of the fires analyzed, researchers determined there were 1,095 "overnight burning events" across 340 fires. All of these events occurred when the wildfire was larger than 1,000 hectares (2,471 acres).
The findings challenge conventional firefighting methods, given the "active day, quiet night" fire cycle. This is based on the idea that the cooler temperatures and higher humidity at night work to slow the growth of wildfires.
"Originally, I had thought that since nights are warming faster than days, higher temperatures and the associated lower relative humidity at night would lead to more overnight fires," wildfire expert Mike Flannigan, a University of Alberta professor emeritus and researcher with Thompson Rivers University, said in a findings summary.
Luo said: "In the extreme cases, there would be no difference between an overnight burn event and daytime burning."
The researchers conclude that daytime drought conditions could act as a "predictor of overnight burning events."
"Nighttime burning has long been overlooked," Luo said. "In a warmer and drier world, we can use daytime drought indicators to predict the night. More of these fires also increase the likelihood of a catastrophic fire."
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about wildfires? Let us know via science@newsweek.com.
Uncommon Knowledge
Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
About the writer
Robyn White is a Newsweek Nature Reporter based in London, UK. Her focus is reporting on wildlife, science and the ... Read more
To read how Newsweek uses AI as a newsroom tool, Click here.
