While forest fires smoke plumes that have swept across large parts of North America, creating fire-breathing thunderstorm clouds.

As can be seen from the image above and others that follow, these pyrocumulonimbus cloudsor pyroCbs, provide a visually dramatic reminder of how extreme forest fire behavior. But they are also important for other reasons.

PyroCbs can hurl lightning bolts toward the ground, sparking even more wildfires. They can also help spread harmful particulate pollution far and wide, and even send smoke into the stratosphere, five to seven miles above the Earth’s surface. Here, the smoke can actually affect the global climate, recent research suggests.

In the photo above is a pyroCb is seen as an eruption of the Oregon Falls Fire on July 15, 2024. The fire has caused a number of these events, including one on July 13 that had the biggest of the summer in the western United States.

EThe Falls Fire started on July 10, 2024, in the Malheur National Forest, about 20 miles northwest of Burns, Oregon. As of today, the fire was only 15 percent contained and was scorched 120,919 acres —an area about two-thirds the size of New York City. The fire was man-made.

I saw a pyroCb explosion above the fire in GOES-18 satellite images taken on July 15. In the following animation of that image, you can see a sudden burst of ashen material near the center of the frame:

Here’s a dramatic video of what the fire looked like from the ground on July 18:

To get an idea of ​​the scale, check out this photo taken the same day, showing a single-engine tanker flying close to the fire:

A pyroCb cloud can form when a forest fire (or volcanic eruption) creates powerful updrafts, lifting ash-like particles high into the atmosphere. As the air cools and expands, water vapor condenses on the particles, creating a gray or brown cloud.

If the rising air currents are strong enough and there is enough water vapor, a large volume of ice particles can form high in the cloud, which helps to create lightning. This in turn can increase the risk of causing more and bigger fires.

“It takes a very large, very hot wildfire to produce an updraft strong enough to lead to pyroCb evolution,” said Scott Bachmeier, recently retired from the University of Wisconsin. Collaborative Institute for Meteorological Satellite Studies.

And aBachmeier’s CIMSS colleague Scott Lindstrom notes, “From my point of view, a pyroCb is most interesting because it injects a lot of particulate matter into the upper troposphere/lower stratosphere, which can then be transported over long distances.”

An increase in fire-breathing smokestorm activity

It has long been known that pyrocumulonimbus clouds rise from volcanic eruptions and nuclear explosions. But the first scientific confirmation The discovery of a pyroCb explosion in a forest fire did not occur until the year 2000.

As the climate warmed and wildfire activity increased, pyroCb outbreaks became larger and more frequent, with record-breaking events in 2017, 2019, 2020, and 2021. In the latter year, an early and unusually warm fire season produced particularly frightening pyroCb outbreaks.

On July 16 of that year, a whopping 10 pyroCbs exploded along the Saskatchewan-Manitoba border in Canada, the largest number scientists had ever seen in a single day in North America since satellite tracking began in 2013. according to NASA.

The outbreak came just two weeks after a monstrous pyroCb blast stunned scientists. It happened when a storm cell grew above a wildfire in British Columbia and spread across more than 62,000 square miles. That’s an area slightly larger than the state of Georgia. This giant cloud sent a chimney of smoke up into the stratosphere, up to 10 miles high.

It turned out to be the largest pyroCb cloud scientists had ever observed in North America.

“The North American Lightning Detection Network recorded nearly 113,000 cloud-to-ground lightning strikes during the event, a large amount for a storm in Canada,” NASA said. “A meteorologist calculated that this single pyroCb event was about 5 percent of the total annual lightning strikes in Canada at once.”

Climate effects

Research published last year in the journal Science showed that black carbon particles rising in the updrafts of pyroCb have a much larger and longer-lasting impact on the stratosphere – and also on the climate – than previously thought.

As part of the study, scientists analyzed 13 years of aerial observations to determine what makes up pyrocumulonimbus smoke and quantify its impact on the stratosphere. The researchers found that pyroCb accounts for as much as 25 percent of the black carbon and organic aerosols in the lower stratosphere. While the climate impact of this material is complex, it is believed that it has a cooling effect by acting as an umbrella.

As the frequency and severity of wildfires increase with ongoing climate change, the impact of pyroCbs is likely to increase as well. But it would be a mistake to think that this will help save us from the ravages of a warming climate.

That’s because the warming impact of the carbon dioxide and other greenhouse gases we continue to pump into the atmosphere is overshadowing the shadowing of particulate matter and aerosols. In addition, CO2 flowing into the atmosphere from forest fires is driving warming. In fact, scientists estimate that the total makes up 5 to 10 percent of annual global CO2 emissions.