Restoration of protective ozone layer is back on track, scientists say
Area appears to be healing after chemicals ended
The protective ozone layer in the upper atmosphere could be restored within several decades, scientists said Monday, as recent rogue emissions of ozone-depleting chemicals from China have been largely eliminated.
In a United Nations-sponsored assessment, the scientists said global emissions of CFC-11, a banned chemical that has been used as a refrigerant and in insulating foams, had declined since 2018 after increasing for several years. CFC-11 and similar chemicals, collectively called chlorofluorocarbons, destroy ozone, which blocks ultraviolet radiation from the sun that can cause skin cancer and otherwise harm people and other living things.
The scientists said that if current policies remained in place, ozone levels between the polar regions should reach pre-1980 levels by 2040. Ozone holes, or regions of greater depletion that appear regularly near the South Pole and, less frequently, near the North Pole, should also recover, by 2045 in the Arctic and about 2066 in Antarctica.
“Things continue to trend in the right direction,” said Stephen A. Montzka, a research chemist with the National Oceanic and Atmospheric Administration and one of the report’s authors. Montzka led a 2018 study that alerted the world that CFC-11 emissions had been increasing since 2012 and that they appeared to come from East Asia.
Investigations by The New York Times and others strongly suggested that small factories in Eastern China disregarding the global ban were the source.
The new emissions had threatened to undermine the Montreal Protocol, the treaty negotiated in the 1980s to phase out the use of chlorofluorocarbons in favor of more benign chemicals after it was discovered that chlorofluorocarbons were depleting atmospheric ozone.
At the time the head of the UN Environment Program, which oversees the protocol, called illegal production of CFC11 “nothing short of an environmental crime which demands decisive action.” Montzka and others had said the rogue emissions, if they continued, could delay recovery of the ozone layer by as long as a decade.
But follow-up studies showed that emissions were declining, a sign the Chinese government was successfully cracking down on the new CFC-11 production. The report said the rogue emissions had most likely delayed ozone layer recovery by a year.
The Chinese CFC-11 was very likely used as a blowing agent in making foam insulation. During foam production, some of the CFC-11 escapes into the atmosphere, where it can be detected and measured, but much of it is contained within the foam as it hardens.
In this way, the researchers said, the Chinese rogue production had contributed to the “banks” of chlorofluorocarbons that were produced worldwide before bans went into effect and are in foams as well as refrigeration equipment and fire-extinguishing systems. These existing chemicals are not yet in the atmosphere, but are being released slowly through foam deterioration and destruction, leaks or other means.
Durwood Zaelke, president of the Institute for Governance & Sustainable Development, a Washington research and advocacy organization, said the elimination of the rogue emissions was another example of the success of the protocol, which is generally considered to be the most effective global environmental pact ever enacted.
Atmospheric monitoring, which is required by the protocol, detected the problem, Zaelke said, and brought it to the attention of the treaty’s directorate. “Without admitting guilt, the offending parties got their act together,” he said. “And the measurements are back where they should be.”
Under the protocol, assessments like the one issued Monday are required at least every four years. In addition to NOAA scientists, contributors included researchers with NASA, the World Meteorology Organization, the UN Environment Program, and the European Commission.
The new assessment was the first to consider the effects on ozone of a potential type of climate intervention, or geoengineering, meant to cool the atmosphere.
The method, called stratospheric aerosol injection, would use airplanes or other means to distribute sulfur aerosols high in the atmosphere, where they would reflect some of the sun’s rays before they reach the surface.
The idea has drawn fierce opposition. Among other objections, opponents say that intervening in the climate in this way could have severe unintended consequences, potentially altering weather patterns worldwide. But many scientists and others say that at the least, research is needed, because warming might reach a point where the world becomes desperate to try such an intervention technique, perhaps temporarily to buy time before greenhouse gas reductions can have a significant effect.