This may not have been the first time that smoke from wildfires affected La Niña significantly. Fasullo and his colleagues are now investigating Australia’s terrible 1974-1975 fire season. In 1975 and 1976, scientists predicted a warm El Niño, but that turned into what researchers called a “aborted El Niño event”, when a cold La Niña formed instead. “It turns out that we have some case studies that we are looking at from the 1970s,” says Fasullo. “We think it may be due to the Australian bushfires.”
That could mean that wildfires play a more active role in La Niña and El Niño than previously believed. “This is especially important given that global warming of the climate will increase the frequency and severity of wildfires,” Xie says. The more the world gets hotter and drier, the bigger and hotter wildfires get, potentially creating more smoke that can drift across the Pacific. The smoke path traveling from Australia is perfectly positioned to interfere with the natural variability of ocean temperatures off the coast of South America.
And there’s another X factor: wildfires are just one source of aerosols in the atmosphere. Others arise from the burning of fossil fuels. Like smoke, they actually help cool the planet by reflecting sunlight and acting as cloud cores. (Particle pollution from cargo ships, for example, is famous for creating “ship tracks” of cooling clouds.) But as humanity switches to green energy, we will produce less of these aerosols, and wildfire smoke aerosols may have an even greater impact.
“We’re pretty confident that anthropogenic aerosols are going to be reduced, which means those natural aerosols could be more important to the climate system,” says Hailong Wang, an earth scientist at Pacific Northwest National Laboratory, who was not involved. in the study. new research.
Incorporating smoke from wildfires into La Niña and El Niño forecasts could make them more accurate. That is essential, because it would allow policy makers to prepare for what is to come. For example, if La Niña ends up causing extreme precipitation, cities must prepare their infrastructure. And if it brings drought, water managers must manage potential supply problems.
Fortunately, with more data and increasingly sophisticated models, the predictions will improve. In June 2020, Fasullo says, the National Oceanic and Atmospheric Administration actually expected neutral conditions in the Pacific. “This was a month before one of the longest La Niña events on record, a kind of historical miss forecast,” says Fasullo. Today, he says, “we still don’t realize the full potential here. But certainly the takeaway from this paper is that wildfires in certain circumstances provide some seasonal predictability that we’re not taking advantage of.”