Lesser-known form of ozone contributes the most to global warming

A new study led by the University of California, Riverside has identified a lesser-known form of ozone that seems to be playing a large role in heating the Southern Ocean – which is one of the Earth’s major cooling systems – by removing a large amount of carbon dioxide and excess heat from the atmosphere. While many previous studies have described the ozone layer in the stratosphere and its crucial role in protecting humans and animals from the sun’s harmful ultraviolet radiation, researchers have now discovered that a form of ozone closer to the ground (tropospheric ozone) can be highly damaging for your planet, by significantly warming up the Southern Ocean.

“People haven’t paid much attention in the past to tropospheric ozone in terms of ocean heat uptake. Based on our models, they should be,” said study lead author Wei Liu, a climate scientist at UC Riverside.

Together with an international team of scientists, Dr. Liu explored climate model simulations with changes in ozone levels between 1955 and 2000. These simulations aimed to isolate both stratospheric and tropospheric ozone from other influences on Southern Ocean temperatures, allowing the researchers to assess how each factor contributes to ocean temperature rises.

While both factors were found to significantly contribute to warming, scientists were surprised to discover that tropospheric ozone played a larger role in this process. “Historically, about a third of the ocean’s warming is attributable to ozone. For this third, about 40 percent is from the stratosphere, and the rest is troposphere,” said Dr. Liu.

According to Dr. Liu and his colleagues, volatile organic compounds (VOCs) from products such as pesticides, automobiles, or tobacco smoke are the gases that form the building blocks of tropospheric ozone, together with nitrogen oxides produced by combustion, and carbon monoxide from gas stoves, furnaces, or automobile exhaust. Most of these products could be modified to produce fewer VOCs. 

“Tropospheric ozone is an air pollutant. If we reduce our production of this, we get the dual benefits of less air pollution and most likely, less Southern Ocean warming as well,” concluded Dr. Liu.

The study is published in the journal Nature Climate Change.

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By Andrei Ionescu, Earth.com Staff Writer