B.C. wildfires triggered mega thunderstorm with volcano-like effects

In the midst of B.C.'s record-breaking wildfire season, the heat from four fires triggered huge thunderstorms that sent smoke flying into the stratosphere, eventually spreading through the entire Northern Hemisphere.

'This was the most significant fire-driven thunderstorm event in history,' meteorologist says

A satellite image shows the path of a plume of wildfire smoke thrust into the stratosphere by a series of fire-triggered thunderstorms in B.C. last August. (Naval Research Laboratory)

The only real comparison for what happened in B.C. on Aug. 12, 2017, would be a volcanic eruption.

On that day, in the midst of the province's record-breaking wildfire season, the heat from four fires triggered huge thunderstorms that sent smoke soaring into the stratosphere, eventually spreading through the entire Northern Hemisphere.

It was the biggest so-called pyrocumulonimbus event ever observed, according to David Peterson, a meteorologist at the U.S. Naval Research Laboratory in Monterey, Calif.

"This was the most significant fire-driven thunderstorm event in history. Nothing else even comes close," Peterson told CBC News.

"The total amount of smoke that was released into the lower stratosphere was comparable to a moderate volcanic eruption."

Pyrocumulus clouds seen from 30,000 feet above the Williams Lake, B.C., area. (Brian McNamara)

These storms, called pyroCb for short, form when conditions are already ripe for thunderstorms. The updraft created by the rapidly rising heat from a wildfire can produce a thunderhead, sparking lightning, rain and wind.

"You end up with these really dirty thunderstorms that act as a large chimney that takes smoke directly from the ground to high altitude — at least to the altitude of aircraft cruising," Peterson said.

Smoke circled the globe

On Aug. 12, the storm activity began in the afternoon, above a wildfire south of the border in Washington state.

Soon, larger thunderstorms were forming over the mammoth Plateau and Elephant Hill fires in B.C., as well as two smaller wildfires in the central part of the province.

Altogether, the event lasted about five hours, but within a few days, the smoke in the stratosphere was stretching from the Arctic to the northern Atlantic Ocean and Europe.

Eventually it reached Asia, and then circled around the globe, lingering for months.

A satellite map from the early hours of Aug. 13, 2017, shows how B.C. wildfires, in pink, triggered large thunderstorms, in green. (Naval Research Laboratory)

The scientists who research this phenomenon have nicknamed the Aug. 12 event "the mother of all pyroCbs" or "the mega pyroCb," according to Peterson.

"This event from 2017 really provided the means to show the world that, hey, this is a major concern," he said.

Cooling and warming effects

A massive event like this could have the potential to affect the climate, much like volcanic eruptions.

The dust and gases thrust into the atmosphere by a volcano can have a cooling effect when they shield the Earth from solar radiation, but they can also contribute to global warming by releasing greenhouse gases.

The exact effect of wildfire-triggered thunderstorms, however, has yet to be determined.

"It's very likely that pyroCbs have a role in the climate system; it's just we're at the early stages of the research," Peterson said.

A graph compares particulate matter thrust into the stratosphere by different wildfires and a volcanic eruption. (Naval Research Laboratory)

About the Author

Bethany Lindsay

Journalist

Reach me at bethany.lindsay@cbc.ca or on Twitter through @bethanylindsay.