Ozone layer is under new threat, says study
New Delhi: Is the ozone layer facing a new threat?
An international team of researchers has found substances such as dichloromethane could endanger the earth’s fragile ozone layer and are not regulated under the current global treaty to stop production of ozone-depleting substances.
The claim was made on Thursday in a study published in Atmospheric Chemistry and Physics, a journal of the European Geosciences Union. The study was carried out by an international team of researchers led by David Oram of UK-based University of East Anglia.
In 1989, the world agreed on a global treaty, the Montreal Protocol, to protect the ozone layer by reducing the production and consumption of ozone-depleting substances.
The study stressed that the Montreal Protocol had helped heal the ozone layer, which reduces the impact on human health from increased exposure to damaging solar radiation, but added that increasing emissions of ozone-destroying substances that are not regulated by the Protocol are threatening the recovery.
It also raised alarm over fast increasing emissions of some short-lived chemicals in East Asia, and showed how they can be carried up into the stratosphere and damage the ozone layer.
“The substances in question were not considered damaging before as they were generally thought to be too short-lived to reach the stratosphere in large quantities,” said Oram.
As per the study, one of the new threats is dichloromethane, a substance with uses ranging from paint stripping to agricultural fumigation and the production of pharmaceuticals. The quantity of dichloromethane in the atmosphere decreased in the 1990s and early 2000s, but over the past decade it has become more abundant.
“This was a major surprise to the scientific community and we were keen to discover the cause of this sudden increase. We expected that the new emissions could be coming from the developing world, where industrialization has been increasing rapidly,” said Oram.
He added that their estimates suggest that “China may be responsible for around 50-60% of current global emissions (of dichloromethane), with other Asian countries, including India, likely to be significant emitters as well.”
The scientists collected air samples on the ground in Malaysia and Taiwan, in the region of the South China Sea between 2012 and 2014 and their analysis revealed presence of “dichloromethane in large amounts” and “1,2-dichloroethane”, which is another ozone-depleting substance used to make PVC.
The study claimed that data collected from a passenger aircraft that flew over South East Asia between December 2012 and January 2014 showed that the substances weren’t only present at ground level but high up in the atmosphere as well.
“We found that elevated concentrations of these same chemicals were present at altitudes of 12km over tropical regions, many thousands of kilometres away from their likely source, and in a region where air is known to be transferred into the stratosphere,” said Oram.
The study also highlighted that emissions of ozone-depleting chemicals in places like China are especially damaging because of cold air surges in East Asia that can quickly carry industrial pollution into the tropics. It means the chemicals can reach the ozone layer before they are degraded and while they can still cause damage.
“It is here that air is most likely to be uplifted into the stratosphere,” said study co-author Matt Ashfold, a researcher at the University of Nottingham Malaysia Campus. “We are highlighting a gap in the Montreal Protocol that may need to be addressed in the future, particularly if atmospheric concentrations continue to rise,” he said.