By-products
“The atmospheric concentration of five theoretically banned chlorofluorocarbons (CFCs) increased between 2010 and 2020,” said Luke Western of the University of Bristol in Britain during a press conference. “In two cases, we don’t understand what’s going on. It’s worrying. »
PHOTO FROM THE UNIVERSITY OF BRISTOL WEBSITE
Luke Western, University of Bristol
The three explainable phenomena described by the study published Monday in the journal Nature Geoscience – ie the increase in the rates of CFC-113a, CFC-114a and CFC-115 – are linked to chemical production. “There is no reason to have so many emissions of these three CFCs,” says another co-author, Stefan Reimann, of the Swiss Federal Laboratories in Dübendorf. “It’s a problem, but we can fix it. »
More worrying: no known industrial process can explain such high levels for the two other CFCs whose levels are increasing. “So it must be unexpected by-products of certain reactions,” Western speculates.
A hole in Antarctica
The hole in the ozone layer is formed in Antarctica, because it takes cold for the chemical reaction involving the CFCs responsible for the destruction of ozone molecules to take place. It peaks in September or October each year. The ozone layer protects the Earth from the Sun’s ultraviolet rays, which notably increase the risk of cancer. As CFCs take a century to degrade, the hole in the ozone layer – which has been shrinking since 2010 – will not disappear until 2080. This hole was detected in 1989 and the production of most CFCs has been banned from 2009.
Warming
For the moment, this increase in the levels of five CFCs has not compromised the absorption of the hole in the ozone layer, according to Mr. Western. “But who knows what awaits us if we don’t tackle the problem? On the other hand, the five CFCs identified in the study of Nature Geoscience aggravate global warming by about 1%, because they are particularly potent greenhouse gases.
Kigali
The successors to CFCs as refrigerants, hydrofluorocarbons (HFCs), are benign to the ozone layer, but have nearly the same global warming potential. For this reason, their elimination and their replacement by other molecules, probably hydrofluoroolefins (HFOs), were provided for in 2016 by the Kigali agreement (ratified in 2017 by Canada and in 2022 by the United States).
“The question now is whether there will be any by-products of HFO production that are CFCs,” Western said. Parisa Ariya, a chemist at McGill University, says the use of HFCs is declining across the West, especially in Canada. “But the ozone layer is complex and its interactions with the climate too,” she warns.
PHOTO FROM MCGILL UNIVERSITY WEBSITE
Parisa Ariya, from McGill University
His colleague Patrick Hayes, from the University of Montreal, is also worried about seeing a new pitfall in the healing of the ozone layer. “It’s quite surprising. After the controversy over illegal CFC emissions in China, here comes another problem. When will this stop? »
The Chinese Enigma
Illegal production of CFC-11 in China was detected in 2018 and factories were shut down. But this remains a delicate subject. “We don’t have access to Chinese data on CFC emissions despite our collaborations with Chinese researchers,” says Western. His colleague Stefan Reimann reports that measuring stations in South Korea can cover part of China. “Let’s say there is room for improvement in data sharing. »
Learn more
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- 100,000 tons
- World annual production of chlorofluorocarbons, early 1990s
Source : Nature
- 47
- Number of countries that have signed the Montreal Protocol, but not the Kigali Agreement
source: un