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Canadian Wildfires Came From Rotten Luck, Not Climate Change
Extreme weather results from a combination of random factors in a complicated system.
By Clifford Mass
June 12, 2023 6:24 pm ET
An extreme environmental event struck New York last week. The city experienced some of the worst air quality in the world—and the worst to hit the city in at least a half-century—as dense wildfire smoke surged south from the province of Quebec. Headlines suggested that the primary culprit was climate change, but these claims are inconsistent with peer-reviewed science, the observational record and our growing understanding of the meteorology associated with wildfire events.
I have published extensively on the meteorology of major wildfires, studied the effects of climate change on atmospheric circulation, and received funding from the National Science Foundation and U.S. Forest Service for research dealing with wildfire meteorology.
An unusual atmospheric circulation resulted in wildfire ignition and rapid growth, with an intense low-pressure area pushing undiluted smoke into the New York area. Global warming was only a minor player in this event.
The recent wildfires occurred in the boreal forests of northern Quebec. Fire isn’t rare in that region. The ecology of these forests relies on fire for the release of seeds and forest health. Many of the major boreal fires occur during a narrow temporal window from mid-April through early June, just after the winter snow has melted and before grasses and other small plants grow, reducing flammability. During this short window, the dead vegetation from the previous year can dry out sufficiently to burn if there is an ignition source such as lightning or errant human activity.
Many of the great Quebec fires have occurred during the spring, such as the May 2010 fire that spread massive amounts of smoke into New England and the May 1870 Saguenay fire, which spread smoke as far as the British Isles. Large boreal forest fires during the spring in Canada are neither unusual nor a sign of climate change.
The fires this month began on June 2, as hundreds of lightning strikes ignited vegetation dried by nearly a week of unusually warm weather. The weather prior to the warm spell wasn’t unusually dry, with the Canadian drought monitor showing normal moisture conditions and temperatures near or below normal.
Starting on May 27, an area of high pressure built over south-central Canada, warming and drying the area for several days into early June. With the light surface fuels, such as grasses ready to burn, all that was needed to start a fire was an ignition source, which occurred in early June with a lightning storm associated with low pressure.
The lightning ignited numerous fires and the low-pressure center’s circulation produced high winds that stoked the fires, resulting in rapid uncontrolled growth. Even worse, as the low center pushed south and intensified east of New York, it produced persistent strong winds from the northwest, moving the Quebec smoke into the New York metropolitan area.
It was the perfect storm for smoke in New York, with several independent elements occurring in exactly the right sequence. It’s difficult to find any plausible evidence for a significant climate-change connection to the recent New York smoke event. The preceding weather conditions over Quebec for the months prior to the wildfire event were near normal. There is no evidence that the strong high pressure over southern Canada that produced the warming was associated with climate change, as some media headlines claim. In fact, there is a deep literature in the peer-reviewed research that demonstrates no amplification of high- and low-pressure areas with a warming planet.
The long-term trend in Quebec has been for both precipitation and temperature to increase. Temperatures have warmed about 2 degrees Fahrenheit over the past half-century. Even assuming that this warming is entirely human-induced, it represents only a small proportion of the excessive heat during the event, in which Quebec temperatures climbed to 20 to 25 degrees above normal. The number of wildfires in Quebec is decreasing; there is no upward trend in area burned, which would be expected if global warming was dominant.
The recent intense New York smoke event is a good illustration of the underlying origins of many extreme environmental and weather events. The atmosphere is a chaotic system, dominated by random natural variability. Such variability is like a game of cards—rarely, by the luck of the draw, one is dealt a full house or a straight flush. Climate change’s effects on weather are relatively small compared to random variations inherent in a hugely complex system.
Mr. Mass is a professor of atmosphere sciences at the University of Washington.
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