New research into the global warming effect of ozone-depleting substances (ODS) confirms that they have played a much larger role in climate change than many previously supposed.
The finding will require a reassessment of carbon dioxide’s pervasiveness in the climate debate, affecting current climate models and future predictions of global and regional temperature changes, especially in the Arctic.
This study in Geophysical Research Letters shows that the warming due to ODSs was more than half of that due to the greenhouse effect of carbon dioxide, that is a about one third of total anthropogenic warming in recent decades.
This is because ODSs have been about 20% more effective than CO2 at causing global warming. In addition ODS warming peaks in the Arctic where it is estimated to be 66% of that due to carbon dioxide.
Ozone-destroying substances have played an important role in Arctic sea-ice loss.
Ozone-depleting substances are chemicals developed in the 1920s and 1930s for use in refrigerators, spray cans and plastic foams. Their use increased rapidly in the 1950s and 1960s. Following the realisation of their devastating impact on the stratospheric ozone layer and the signing of the Montreal Protocol in the 1987 their phase-out is underway.
It is well known that ODSs are powerful greenhouse gases, estimated to have the second largest warming effect between 1955 and 2005 as reported in 2020 in Nature Climate Change. Building on this work is the aim of this research carried out by scientists from Canada, The United States, Britain and Austria.
Analysing all but one climate forcing factors they find that between 1955–2005 ODSs are responsible for 30% of global warming, 37% of Arctic warming, and 33% of summertime Arctic sea ice loss. In addition, they find that the impact of ODSs on global temperatures is about 20% larger than expected based on the impacts they have on the Earth’s radiative balance.
What is particularly surprising say the researchers is that ODSs have contributed considerably to Arctic warming and sea ice loss in the second half of the 20th century. This research adds to the evidence that ODSs have played a more significant role in historical climate change than appreciated.