A fire big enough to make its own lightning used to be as rare as it sounds.
But the McKinney fire, which broke out Friday, sparked four separate thunder and lightning storms in the first 24 hours alone. A deadly combination of intense heat, parched vegetation and arid conditions has turned the 55,000-acre fire in the Klamath National Forest into its own natural force.
On four separate occasions, columns of smoke rose from the flames above the height at which a typical fighter jet flies, penetrated the stratosphere and injected a plume of soot and ash miles above the Earth’s surface. It’s a phenomenon known as a pyrocumulonimbus cloud, a byproduct of fire that NASA once memorably described as “the fire-breathing dragon of clouds.”
In Siskiyou County, the water in these clouds returned to Earth as rain, accompanied by thunder, wind and lightning, in “a classic example of a wildfire producing its own weather,” said David Peterson, a meteorologist with the U.S. Naval Research Laboratory, which has developed an algorithm to distinguish fire-induced thunderstorms from traditional thunderstorms.
Investigators have yet to determine the cause of the McKinney fire, which grew rapidly in hilly, challenging terrain and was out of control as of Tuesday.
Mike Flannigan, a fire scientist at Thompson Rivers University in western Canada, said he is not shocked to see such powerful fires. The numbers have been pointing in that direction for years. He just didn’t think they would happen so soon.
“What we’ve been seeing in the western United States and in British Columbia in recent years, I didn’t expect until 2040,” Flannigan said. “The signal is clear: this is due to human-induced climate change. It couldn’t be more obvious than that. It’s going faster than I expected. This is my field and it is surprising how quickly things change.”
It’s not just that wildfires are more powerful, more frequent and burn more acreage each year than ever before, he said. The energy generated by these fires also creates columns of smoke so large that they leave the troposphere, the bottom layer of the atmosphere that envelops the Earth “like an apple peel,” as Flannigan put it.
The troposphere is where the weather strikes, and where dazzling clouds of smoke and soot circulate, even from medium-sized fires. But when a column of smoke like the one from the McKinney Fire blasts through that layer and enters the stratosphere — the higher, more stable layer above it — it wreaks havoc with the local weather and seed the Earth’s atmosphere with aerosol pollutants whose effects science still sorts out.
Days before the McKinneyfire broke out, researchers at the University of Utah published a new study in the journal Scientific Reports documenting the growth of smoke plumes in wildfires for most of the past two decades.
The team looked at 4.6 million measurements of smoke plumes recorded in the western US and Canada between 2003 and 2020. The data was taken hourly from fires burning in August and September in each of those 18 years.
In four of the geographic regions they surveyed, maximum smoke plume heights increased by an average of 320 feet per year. The most pronounced growth was in California’s Sierra Nevada, where maximum plume heights rose an average of 750 feet in each year of their study.
“If we have climate trends that encourage faster fire spread, more intense wildfire activity, and greater heat flow from these fires, we can expect higher plume heights,” said Kai Wilmot, a postdoctoral researcher in atmospheric sciences at the University of Utah and a co-author of the study. study.
Not only are these smoke columns bigger, Wilmot and his colleagues noted, but with each passing year, they also became more densely packed with microscopic bits of soot and ash. This particulate matter pollution, known as PM2.5, is associated with asthma, cardiovascular problems and premature death.
And some of the country’s most intense growth in smoke emissions has come from the Klamath region. The data is unclear on how much the height of Klamath smoke increases, Wilmot said, but the concentration of harmful particulate pollution emanating from the clouds is certainly increasing.
A paper the team published last year on fire data from 2000 to 2018 highlighted the Klamath region as a hotspot of emissions, especially in the month of August.
“It just felt like the McKinney Fire was like clockwork,” Wilmot said. “We are on the eve of August. It’s hot and dry. It’s right in the Klamath. And then at night, boom.”
The height of the plume is a function of both atmospheric conditions, such as higher temperatures and reduced humidity, and the size of the fire, which is largely determined by the amount of dry vegetation available to burn. The Klamath area has all those qualities in abundance.
California is in the midst of its worst drought since records began. The average summer temperature in California is now 3 degrees higher than it was at the end of the 19th century.
The days before the fire were a sweaty mess of triple-digit temperatures and low humidity, further drying out the plants from a dry winter. The fire started in an overgrown area previously used for logging, resulting in fewer fire-resistant old trees and many smaller and highly flammable younger trees.
When plants burn, the carbon stored in their leaves is released into the atmosphere, contributing to the concentration of greenhouse gases. But as the Utah team noted, fires also spew tons of particulate matter.
At less than 2.5 microns in diameter, these tiny pollution particles can be inhaled deep into the lungs if inhaled here on the ground. In the stratosphere, they wreak a different kind of havoc that scientists don’t yet fully understand.
“The more we know about smoke, the more we know it’s bad for us,” Flannigan said.
Before massive climate change-induced wildfires, volcanoes were the main vehicle sending soot into the stratosphere.
Scientists studying the aftermath of Australia’s massive 2019 and 2020 wildfires calculated that their emissions were comparable to those of a medium-sized volcanic eruption.
Earth’s geological record shows that over time, these particles can act as a cooling system, deflecting the sun’s radiation before it can enter the atmosphere. But it is a complicated dance. Separate research from MIT into the Australian fires found that their plumes of smoke are depleting the ozone layer, which protects the Earth from ultraviolet radiation.
The long-term consequences are not clear. We simply don’t have millennia of data on the planetary effects of human-aggravated megafires, as we do with volcanoes.
Social media is full of it video clips of volcanic-like clouds floating to the sky of the Klamath National Forest. They will be more common, as will fires powerful enough to generate their own lightning.
“The trend is to see more and more of these suckers,” Flannigan said. “It’s terrible, but we have to learn to live with it.”