Wildfires Had a Bigger Climate Impact Than the Pandemic in 2020

Smoke from the 2019-2020 Australian bushfires, as seen from space.

Smoke from the 2019-2020 Australian bushfires, as seen from space. NASA

While pandemic-related lockdowns led to a dramatic drop in greenhouse gas emissions last year, the event that had the biggest impact on the climate in 2020 was actually a series of devastating bushfires in Australia, according to a new study.

Using computer modeling, researchers compared the effect of both the drop in vehicle emissions and industrial activity during the pandemic with smoke released by the Australia wildfires. They found that the decline in pollution during lockdowns produced clearer skies, allowing more sunlight to reach Earth, thereby warming the planet by around 0.05 degrees C. Smoke from the Australian bushfires, on the other hand, blocked sunlight, cooling the planet by around 0.06 degrees Celsius. The findings were published in the journal Geophysical Research Letters.

“What this research shows is that the impact of regional wildfire on global climate can be substantial,” said John Fasullo, a scientist at the National Center for Atmospheric Research and lead author of the study. “There are large-scale fingerprints from the fires in both the atmosphere and ocean. The climate response was on par with a major volcanic eruption.”

Over the long run, economic lockdowns or slowdowns will help keep warming in check by reducing greenhouse gas emissions, while wildfires will add to warming by releasing more heat-trapping carbon dioxide into the atmosphere.

Wildfires are expected to grow more intense in the years to come, as the last century of fire suppression has left forests full of vegetation that has been desiccated by hot, dry conditions. But a new study of forests in California’s Sierra Nevada mountains suggests that, following a decade-long burst of wildfires, such blazes are expected to grow smaller as trees are consumed by fires or killed off by drought. Those findings were published in the journal Ecosphere.

“The buildup of fuels, in conjunction with the increasingly hot and dry conditions, leads to these very large, catastrophic fire events,” said Maureen Kennedy, an ecologist at the University of Washington Tacoma and lead author of the study. “But our simulations show that if you allow fire to continue in an area, then the fire could become self-limiting, where each subsequent fire is smaller than the previous one.”