London, Feb 17:
The ozone layer faces a new threat as certain chemicals which have historically contributed little to ozone depletion are now on the rise, warn researchers.
These chemicals are not controlled by a UN treaty designed to protect the ozone layer.
Atmospheric abundance of one of these ‘very short-lived substances’ (VSLS) is growing rapidly, the researchers reported.
“VSLS can have both natural and industrial sources. Industrial production of VSLS is not controlled by the United Nations Montreal Protocol because historically these chemicals have contributed little to ozone depletion,Â” said study lead author Ryan Hossaini from University of Leeds in Britain.
“But we have identified now that one of these chemicals is increasing rapidly and, if this increase is allowed to continue, it could offset some of the benefits to the ozone layer provided by the Montreal Protocol,” Hossaini added.
In the study, the researchers used a 3D computer model of the atmosphere to determine the impact of VSLS on ozone and climate.
Measurements of VSLS in the atmosphere over the past two decades, provided by collaborators from the National Oceanic and Atmospheric Administration (NOAA) in the US, were also analysed.
These measurements revealed a rapid increase in atmospheric concentrations of dichloromethane, a man-made VSLS used in a range of industrial processes.
The researchers found that while the amount of ozone depletion arising from VSLS in the atmosphere today is small compared to that caused by longer-lived gases, such as CFCs (chlorofluorocarbon), VSLS-driven ozone depletion was found to be almost four times more efficient at influencing climate.
The researchers also separated out natural sources of VSLS – such as seaweed in the ocean – and those released due to human activity – such as industrial processes – in order to determine the relative importance of each.
At present, naturally-emitted VSLS account for around 90 percent of the total ozone loss caused by VSLS in the lower stratosphere.
However, the contribution from man-made VSLS compounds is increasing and appears set to increase further in coming years, the researchers noted.
The study was published in the journal Nature Geoscience. IANS