The first faint pall of smoke drifted into the New York area on June 1. Most people didn’t notice the slight haze in the air, which originated from a cluster of wildfires near Halifax, Nova Scotia. But worse was on the way. By June 6, much of the eastern U.S., including New York City and Washington, D.C., was smothered by a blanket of fine particles, drifting down mostly from Quebec. In many areas, people could smell smoke, even though the wildfires producing it were roughly 800 miles away.

Predictably, these unsettling conditions set off a blaze of apocalyptic headlines and pronouncements linking the conditions to climate change. “There’s no escaping climate’s threat to health,” wrote the Washington Post. The New York Times predicted the coming summer will be a “season of climate extremes.” President Biden called the smoke event “another stark reminder of the impact of climate change.” White House Climate Envoy John Kerry announced, “Today’s generation is facing its very own climate D-day.”

These days, every strange or extreme weather event is an opportunity for climate advocates to try to rally the public behind more ambitious climate actions. The urge is understandable. In truth, the most dramatic climate claims are predictions about how a warming planet will affect vulnerable ecosystems and human life in the future. Those possible outcomes might sound dire, but they don’t have much bearing on people’s day-to-day lives. Therefore, climate activists and policymakers believe that the best way to build support for bolder policies is to convince the public that climate change is having a dramatic impact on their lives today. If people believe that we’re entering an era of nonstop hurricanes, tornados, and wildfires, they’ll be more likely to back expansive plans, say, to abandon fossil fuels. A massive pall of smoke streaming over both the nation’s capital and its major media hub motivated climate activists to raise the alarm.

The idea that a warming climate will produce more and bigger wildfires isn’t implausible. Research suggests that warmer, drier conditions extend the periods of “fire weather” when blazes are more likely to start and spread. But evidence that climate change is driving a dramatic increase in wildfires remains both sparse and contested. While some climate scientists latch on to extreme weather or fire events as an opportunity to raise awareness, others warn against attributing every unusual episode to human activity. The media, of course, always come down on the side of maximum alarm. Ryan Maue, a prominent meteorologist often described as a “lukewarmist” on climate, wrote on Twitter, “We can ‘blame climate change’ for extreme weather events like fires, or floods, but we still need to explain ‘how/why’ they happened. However, there does not seem to be much effort or interest by corporate media to provide such information.”

Was the unusual spate of wildfire smoke over the eastern U.S. primarily the result of a rapid, inexorable climate trend? Or were other, more immediate factors involved? While the role of climate change can’t be ruled out, the surge of Canadian smoke appears to be primarily attributable to a unique combination of factors, a kind of perfect storm for producing an emergency to the south.

First, a rare weather event spawned an enormous number of fires almost simultaneously. On June 1, a wave of thunderstorms swept across Quebec from the northwest. A geostationary satellite operated by the National Oceanic and Atmospheric Administration (NOAA) caught the flashes of thousands of lightning strikes moving in an arc across the province. The timber was exceptionally dry, so many of these strikes started tiny blazes. Under normal conditions, most of these—many involving perhaps a single tree—would have petered out on their own. But the next day came an untimely shift in the winds: a high pressure ridge over the Atlantic pushed an air mass across Quebec from the northeast. Satellite images show dozens of smoke plumes erupting almost at once as the strong winds literally fanned the flames. (The sudden emergence of so many fires also led to various conspiracy theories concerning their origin. But the satellite data show that no malevolent human action was required.)

Before the arrival of humans in North America, of course, all fires were the result of lightning strikes. Humans—both Native Americans and European colonists—brought a more intense regime of fires to the continent, sometimes accidentally, but often deliberately as a way to clear forests or manage ecosystems. In the nineteenth and early twentieth centuries, American forests burned at rates dramatically higher than current ones. Today, humans still cause most wildfires. But fires caused by lightning tend to grow larger, probably because they’re often in inaccessible locations and are less likely to be caught early. By June 3, more than 150 wildfires were burning across Quebec, while attempts to control them had barely begun.

Normally, westerly winds blow smoke from eastern Canadian wildfires across the thinly populated eastern provinces and out to sea. But another quirk of the weather pushed the smoke to the south. Since early May, the entire U.S. has been in the grip of an atmospheric formation known as an Omega Block. These weather patterns, most common during winter, form when zones of high and low pressure alternate across the continent, with low pressure over California, high pressure over the mountain or central U.S., low pressure in the east, and high pressure again over the Atlantic. That pattern forces the jet stream into a wild roller coaster pattern: dipping low over the Pacific, high into northern Canada, then zooming down through the Midwest, and finally turning north again over the Atlantic. This inverted “U” pattern resembles the Greek letter Omega, hence the name. It’s called a “block” because the pattern tends to lock the zones of high and low pressure in place; the whole formation can remain almost stationary for weeks at a time.

This bowl of low pressure over the eastern U.S. slowly rotates counter-clockwise, pulling in air—or smoke—from Canada. And because the system is locked in place, there are no typical westerly winds to push the whole mess out to sea. That allowed the air pollution to build up. Atmospheric scientists track particulates measuring 2.5 micrometers or smaller. These ultrafine particles are especially dangerous because they can be inhaled deeply in the lungs and even enter the bloodstream. On June 8, particulate levels in New York City reached a stunning 868 micrograms per cubic meter. (The EPA considers 35 micrograms to be a safe average level.)

Climate activists hope the public will perceive this extraordinary event as the “new normal” in a warming climate. In fact, it is hard to parse how much climate change plays a role in the smoke emergency, versus the bad luck of a spate of major fires coinciding with an unusual weather pattern. The media treat the claim that climate change is producing more wildfires as settled science. In fact, the Intergovernmental Panel on Climate Change (IPCC) regards the question with much more nuance. The panel does not measure fire trends directly, but rather tracks changes in “fire weather”—in other words, “conditions conducive to triggering and sustaining wildfires.” The IPCC concludes with “medium confidence” (that is, with a 50–50 certainty) that weather conditions promoting wildfires “have become more probable” in certain regions including North America. The IPCC’s current report predicts with high confidence that fire weather will increase in some parts of the globe by 2050. Notably, those regions do not include eastern North America.

Of course, fire weather is only one factor involved in producing wildfires. As the somewhat contrarian climate scientist Roger Pielke Jr. observes, “most wildfires are started by human activity.” In a sense, that’s a promising point since it means humans have some control over the frequency of fires. Indeed, as the IPCC concludes, total “biomass burning” has declined over the past century. What about Canada specifically? Data from Canada’s National Forestry Database show that the average number of fires per year has declined since 1990, while the total number of acres burned has increased somewhat. In Quebec alone, no upward trend has been seen in either the number of fires or acreage burned. As Pielke notes, “Things are worse this year, but they have not been getting worse. In fact, the last 8 years had extremely low area burned.”

Should analysts and media observers treat 2023’s massive eruption of Quebec wildfires—and the concomitant smoke pouring southward—as confirmation that global warming is to blame? Or should we regard the unlikely combination of numerous fires and the Omega Block weather pattern as an extreme outlier (which, in historical terms, it is)? Treating every severe weather event as proof that the climate apocalypse has arrived does a disservice to the public. And it misrepresents climate science itself, which is complex and nuanced on the relationships between warming and weather. When the media hype outlier events as inevitable products of climate change, they lay the groundwork for a backlash: If we claim every severe fire year is due to climate change, how do we explain recent seasons that had very few fires? Might those be used to prove that climate claims are overblown? The best approach is not to ignore outlier events, nor to exaggerate them, but carefully to add each new episode to the data set and avoid overheated conclusions.

Photo by Lokman Vural Elibol/Anadolu Agency via Getty Images


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