Study: Where there’s smoke, there’s worse wildfires

The smoke from wildfires can change the weather and make fires more destructive, a new study has found. 

The study published on Thursday in Science emphasized the disruptive impacts of the smoke from large wildfires on the weather patterns of entire regions — driving blazes to more destructive heights. 

The study tells the inside story of one of the U.S.’s most destructive fires — and raises a broader cautionary note about the unpredictable ways that fires can interact with the winds and waters of coastal forests. 

The team of scientists had a rare chance to observe this relationship in action when the enormous August Complex fire broke out in northern California in the summer of 2020. 

That fire was a conflagration formed as lightning ignited four smaller — though still large — wildfires, which converged throughout August 2020. 

The composite wildfire would burn for four months, rampaging across more than a million acres, according to the Forest Service. 

Smoke from the fire was so intense that it dimmed the sun, cutting California’s solar production by up to 30 percent, scientists at the National Center for Atmospheric Research found. 

But for the international team of scientists, the destructive fire represented a rare opportunity: a natural experiment on the impacts that the smoke plumes pouring off the fire could have on regional weather — and therefore on the fire itself. 

The collaboration between China’s National Natural Science Foundation and North Carolina Central University used satellite data, ground observations, and a computer model that combined weather and chemistry information to track the complex dance of smoke, weather and fire.  

Their findings showed how the smoke generated by the August Complex fire played a significant role in fueling its growth. 

As smoke poured off the fire, it created a thick, dense layer of floating microscopic soot that both trapped heat and blocked sunlight from reaching the ground. 

This combination of a hot atmosphere and shaded ground created an unstable thermal layer cake of heat. As the hot smoke rose rapidly along the broad fire front, it pulled in powerful east-blowing winds — which fed the growing fire, producing more smoke. 

That, in turn, led to the formation of new weather patterns that intensified the winds — drying the land beneath into tinder, and further stoking the fire. 

These findings, however, were specific to the Mediterranean climate of California, and of European countries like Spain, which sit at the mountainous border between a hot, dry landmass and a cold ocean. 

In mainland Southeast Asia, the team found that smoke led to similar destruction by different means. In the fires that burned across the region in 2004, the researchers found the opposite result: smoke from the fires combined with the humid monsoon-season air to produce thunderstorms. 

The storms formed as the smoke — which covered nearly all of Southeast Asia — cooled the land as the sea continued to warm. As the two temperatures converged, a spinning cyclone emerged that blocked the annual monsoons that would usually have dumped rain on both the fires and the forests they were expanding into.  

This in turn meant a larger and more dangerous fire – because of the flames but, even more significantly, because of the toxic impacts of chronically breathing smoke. 

The scientists’ advice was simple: suppressing a potentially large fire early meant a bigger chance of interrupting this feedback loop before it could properly get started. 

The group said that new tools for remote sensing, chemical detection and supercomputing had made it ever more possible to identify “amplifier regions” where early forecasting could “avert some extreme wildfires.”