A fire large enough to produce its own lightning was once as rare as it seems.
But the McKinney fire, which erupted on Friday, generated four separate thunder and lightning storms in its first 24 hours alone. A lethal combination intense heat, parched vegetation and dry conditions turned the 55,000 acre fire in the Klamath National Forest into its own force of nature.
Four distinct times, columns of smoke rose from the flames beyond the altitude at which a typical jet flies, penetrating the stratosphere and injecting a plume of soot and ash miles above the surface of the Earth. It’s a phenomenon known as the pyrocumulonimbus cloud, a byproduct of the fire that NASA once used memorably described as “the fire-breathing dragon of the clouds”.
In Siskiyou County, water from 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 at the US Naval Research Laboratory, who developed an algorithm to distinguish fire-induced thunderstorms from traditional thunderstorms.
Investigators have yet to determine the cause of the the McKinney firewhich developed rapidly over hilly and difficult terrain and had not been confined since Tuesday.
Mike Flannigan, a fire specialist at Thompson Rivers University in western Canada, said he was not shocked to see such powerful fires. The data has been pointing in this direction for years. He just didn’t think it would happen so soon.
“What we’re seeing in the western United States and British Columbia over the past few years, I didn’t expect to see until 2040,” Flannigan said. “The signal is clear: this is due to human-induced climate change. It can’t be clearer than that. It’s happening faster than I thought it would. It’s my field, and it’s amazing how quickly things change.
It’s not just that forest fires are more powerful, more frequent and burning more area each year than ever before, he said. The energy generated by these conflagrations also creates columns of smoke so large that they leave the troposphere, the lower layer of the atmosphere that envelops the Earth “like an apple skin”, as Flannigan put it.
The troposphere is where the weather happens and where clouds of scorching smoke and soot circulate even from medium-sized fires. But when a column of smoke such as that emanating from the McKinney Fire passes through this layer and into the stratosphere – the highest and most stable layer above it – it wreaks havoc with local weather and wreaks havoc. earth’s atmosphere with polluting aerosols whose consequence science is still sorting out.
A few days before the McKinney fire broke out, researchers from the University of Utah published a new study in the journal Scientific Reports documenting the growth of smoke plumes in wildfires over most of the past two decades.
The team examined 4.6 million smoke plume records recorded in the western United States and Canada between 2003 and 2020. Data was taken hourly from fires burning in August and September in each of those 18 years.
In four of the geographic regions they examined, the maximum height of the smoke plume increased by an average of 320 feet per year. The most pronounced growth of all occurred in the Sierra Nevada of California, where the maximum plume height increased by an average of 750 feet each year of their study.
“If we have climate trends that encourage faster spread of fires, more intense wildfire activity, greater heat flux from those fires, we can expect a higher plume height,” said said Kai Wilmot, postdoctoral researcher at the University of Utah in atmospheric sciences and a co-author of the study.
These smoke columns are not only taller, Wilmot and his colleagues noted, but over the years they have also become more densely filled with microscopic bits of soot and ash. This fine particle pollution, known as PM2.5, is linked to asthma, cardiovascular problems and premature death.
And some of the most intense growth in smoke emissions in the country is coming from the Klamath region. The data is unclear on Klamath’s smoke height increasing, Wilmot said, but the concentration of harmful polluting particles emerging from its clouds is certainly increasing.
A article that the team published last year review of fire data from 2000 to 2018 highlighted the Klamath region as an emissions hotspot, particularly in the month of August.
“It felt like the McKinney fire was like clockwork,” Wilmot said. “We are just at the dawn of August. It is hot and dry. It’s just in the Klamath. And then overnight, boom.
The height of the plume is a function of both atmospheric conditions, such as higher temperatures and decreased humidity, as well as the size of the fire, which is largely determined by the amount of dry vegetation available to burn. The Klamath region has all of these qualities in abundance.
The days leading up to the fire were a clammy mess of triple-digit temperatures and low humidity, which further dried out plants already parched by a dry winter. The fire broke out in an overgrown area previously used for logging, which meant fewer fire-resistant old trees and many more smaller, easily flammable young ones.
When plants burn, the carbon stored in their leaves is released into the atmosphere, increasing the concentration of greenhouse gases. But as the Utah team noted, the fires also spit out tons of fine particles.
Measuring less than 2.5 microns in diameter, these tiny particles of pollution can be inhaled deep into the lungs when breathed in here on the ground. In the stratosphere, they wreak another 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 the massive forest fires induced by climate change, volcanoes were the main vehicle that sent soot into the stratosphere.
Scientists studying the aftermath of the massive fires of 2019 and 2020 in Australia have calculated that their emissions were equivalent with that of a medium-sized volcanic eruption.
Earth’s geological records show that over time, these particles can act as a cooling system, deflecting solar radiation before it can enter the atmosphere. But it’s a complicated dance. Separate research from MIT on the Australian fires discovered that their plumes of smoke depleted the ozone layer, which protects the Earth from ultraviolet radiation.
The long-term consequences are unclear. We simply don’t have millennia of data on the planetary effects of human-aggravated mega-fires, as we do with volcanoes.
“The trend is to see more and more of these suckers,” Flannigan said. “It’s horrible, but we have to learn to live with it.”