Recovery of the ozone layer in the Earth’s atmosphere needs to be considered while developing climate policies, researchers said, after their study estimated the gas could warm the planet 40 per cent more than what was previously thought.
Ozone — which shields the Earth from harmful ultraviolet rays in sunlight — takes on a more harmful role closer to ground by acting as a greenhouse gas and trapping heat.
The gas might become the second biggest contributor to global warming by 2050, following carbon dioxide, findings published in the journal ‘Atmospheric Chemistry and Physics’ suggest.
The researchers, led by those from the UK’s University of Reading, found that during 2015-2050, ozone could be expected to cause 0.27 watts per square metre of extra warming — a measure of how much extra energy gets trapped per square metre of Earth’s surface.
The result would make ozone the second largest contributor to global warming by mid-century after carbon dioxide (estimated to cause 1.75 watts per square metre of extra warming).
“We find robust increases in ozone due to future increases in ozone precursors and decreases in (ozone-depleting substances),” according to the authors.
“This increase makes ozone the second largest contributor to future warming by 2050 in this scenario, approximately half of which is due to stratospheric ozone recovery and half due to tropospheric ozone precursors,” they wrote.
Studies have found signs of recovery in the atmosphere’s ozone layer due to countries banning chemicals known to cause damage, including chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), under the 1987 Montreal Protocol.
“However, while this helps repair the protective ozone layer, we have found that this recovery in ozone will warm the planet more than we originally thought,” lead author William J Collins, a professor of atmospheric chemistry and earth system modelling at the University of Reading, said.
“Air pollution from vehicles, factories and power plants also creates ozone near the ground, causing health problems and warming the planet,” Collins said.
Banning the production of CFCs and HCFCs to save the ozone layer was also expected to help fight climate change.
However, healing of the ozone layer creates more warming that cancels out most of the climate benefits achieved from removing CFCs and HCFCs, thereby resulting in fewer climate gains accrued than previously estimated, the researchers said.
They added that while addressing air pollution can limit ozone from forming close to the ground, a continued recovery of the ozone layer will create an unavoidable warming.
The team suggested an update of climate policies to account for ozone’s larger warming effect.