The hole in the Earth’s ozone layer, once the greatest environmental threat humanity has faced, should be fully healed in most of the world within two decades after decisive action by governments to phase out ozone-depleting substances, a new UN assessment has found. .
The loss of the ozone layer, which has put people at risk of exposure to the sun’s harmful ultraviolet rays, is on track to be fully recovered by 2040 worldwide, except in the polar regions, the report said. The poles will take a little longer – the ozone layer will fully return by 2045 over the Arctic and 2066 over the Antarctic.
After alarms about ozone depletion in the 1980s, the ozone layer has steadily improved since the 1989 Montreal Protocol, an international agreement that helped eliminate 99% of ozone-depleting chemicals such as chlorofluorocarbons (CFCs) that were used as solvents and refrigerants.
The UN said action on the ozone layer also prompted a tougher response to the climate crisis – CFCs are also greenhouse gases and their continued unchecked use would raise global temperatures by as much as 1C by mid-century, exacerbating an already dire situation in which gases that warming the planet still not decreasing.
“Ozone action sets a precedent for climate action,” said Peteri Thalas, secretary-general of the World Meteorological Organization, which presented the progress report, which is done every four years, on Monday. “Our success in phasing out ozone-depleting chemicals shows us what can and must be done urgently to transition away from fossil fuels, reduce greenhouse gas emissions, and thus limit temperature rise.”
A unified global response to tackling CFCs means the Montreal Accord should be considered “the most successful environmental treaty in history and offers encouragement that countries around the world can come together and decide on an outcome and act on it,” says David Fahey, a scientist at To the National Oceanic and Atmospheric Administration, which is the lead author of the new assessment.
Progress hasn’t always been smooth – in 2018, scientists discovered an increase in the use of CFCs, which was traced to China and eventually remedied. Meanwhile, replacing CFCs with another group of industrial chemicals, hydrofluorocarbons (HFCs), has been problematic because HFCs are greenhouse gases, requiring a further international agreement, made in Kigali, to limit their use.
Fahey said that even with swift global action on CFCs, the chemicals still remain in the atmosphere for about a century. “It’s a bit like waiting for paint to dry, you just have to wait for nature to do its thing and get these chemicals out,” he said.
The challenge with greenhouse gases like carbon dioxide is even greater, he said, because they stay in the atmosphere much longer and, unlike CFCs, which were produced by only a few companies, emissions come from fossil fuels are far more widespread and embedded in almost every activity in societies.
“CO2 is another order of magnitude in terms of its longevity, which is sobering,” he said. “Getting every person on the planet to stop burning fossil fuels is a completely different challenge.”
The latest UN progress report is the first to address the potential impact of solar geoengineering on the ozone layer, a proposed climate intervention where reflective particles such as sulfur are sprayed en masse into the atmosphere to reflect sunlight and thereby reduce global warming.
The controversial practice, which the US government wants to investigate, has the potential to reduce global temperatures but could have “unintended consequences, including effects on ozone,” the report said, although it acknowledged “many knowledge gaps and uncertainties prevent a more robust evaluation in this moment”.
Fahey said that adding large amounts of sulfur to the stratosphere could reduce ozone, although probably by less than 10% and would not cause a “collapse” in the ozone layer.
“These types of climate interventions are sensitive topics because they are a tangled mess of ethics and governance, not just science,” he said. “However, there would indeed be ozone consequences if you put enough sulfur into the atmosphere.” It would be inevitable.”