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March 1,2022

Anna Murray 

Atmospheric chemists at the Massachusetts Institute of Technology (MIT) discovered that the smoke from those fires triggered chemical processes in the stratosphere, resulting in ozone loss, which protects the Earth from incoming ultraviolet radiation. The study, "On the stratospheric chemistry of midlatitude wildfire smoke," published on February 28 in the Proceedings of the National Academy of Sciences, is the first to establish a chemical link between wildfire smoke and ozone depletion.

The study was co-authored by Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Science at MIT, and Kane Stone, a research scientist in MIT's Department of Earth, Atmospheric, and Planetary Sciences, as well as collaborators from the University of Saskatchewan, Jinan University, the National Center for Atmospheric Research, and the University of Colorado at Boulder.

As global warming causes stronger, more frequent wildfires, wildfire smoke could have a significant long-term impact on ozone. Massive wildfires have been known to generate pyrocumulonimbus clouds, which can reach the stratosphere, the layer of the atmosphere between 15 and 50 kilometers above the Earth's surface. 

Professor Solomon discovered in 1989 that particles from major volcanic eruptions can reach the stratosphere and deplete ozone through a series of chemical reactions.

The wildfires that raged across Australia in 2019 and 2020 were unprecedented. The smoke from Australia's wildfires reached stratospheric altitudes of up to 35 kilometers. In their new study, Professor Solomon and her colleagues looked at how nitrogen dioxide concentrations in the stratosphere changed after the Australian bushfires. If these levels fall significantly, it would imply that wildfire smoke depletes ozone through chemical interactions similar to those observed in volcanic eruptions.