This may not have been the first time smoke from wildfires had significantly affected La Niña. Fasullo and his colleagues are now investigating Australia’s infamously terrible 1974-1975 fire season. In 1975 and 1976, scientists had predicted a warm El Niño, but that turned into what researchers instead called a “aborted El Niño event‘, when a cool La Niña emerged instead. “It turns out we have some case studies from the ’70s that we look at,” says Fasullo. “We think it may be due to 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 as background climate warming will increase the frequency and severity of wildfires,” says Xie. The more the world warms and dries, the bigger and hotter wildfires become, potentially creating more smoke that can drift across the Pacific Ocean. The smoke route traveling from Australia is perfectly positioned to mess 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, these actually help cool the planet by reflecting sunlight and acting like cloud cores. (Particle pollution from cargo ships, for example, is known for creating “ship trails” from cooling clouds.) But as humanity transitions to green energy, we’ll be producing fewer of these aerosols, and smoke aerosols from wildfires could have even more of an impact.
“We’re pretty sure that anthropogenic aerosols will decrease, so that means those natural aerosols could be more important to the climate system,” said Hailong Wang, an earth scientist at Pacific Northwest National Laboratory, who was not involved in the new research. .
Including wildfire smoke in La Niña and El Niño forecasts could make them more accurate. That is critical, as it would allow policymakers to prepare for what is to come. For example, if La Niña causes extreme precipitation, cities need to get their infrastructure ready. And if it brings drought, water managers must address potential supply issues.
Fortunately, with more data and increasingly sophisticated modeling, predictions get better. In June 2020, Fasullo says, the National Oceanic and Atmospheric Administration actually expected neutral conditions in the Pacific Ocean. “This was one month before one of the longest La Niña events on record — kind of a historically missed forecast,” says Fasullo. Today, he says, “we still don’t understand the full potential here. But what we can gather from this article alone is that wildfires in certain circumstances offer some seasonal predictability that we don’t take advantage of.