Climate The ozone layer on the right path to recovery

Climate: The ozone layer on the right path to recovery

Discovered in the 1980s, the hole could be absorbed in 10 to 40 years, according to the United Nations. The Paris target of +2°C is still a long way off.

The ozone hole could be reduced within four decades, but potential solar geoengineering projects to limit global warming could have undesirable effects, scientists warned Monday (January 9).

“If current guidelines remain in place, the ozone layer is expected to recover to 1980 levels (before the hole appeared) by around 2066 over Antarctica, 2045 over the Arctic, and 2040 in the rest of the world,” says the UN -Environment on in its four-year estimate.

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Recovery through international cooperation

“The phasing out of almost 99% of banned ozone-depleting substances has helped preserve the ozone layer and has been instrumental in its recovery in the upper stratosphere and in reducing human exposure to harmful ultraviolet (UV) rays from the sun,” note the experts commissioned by the UN.

The ozone hole was caused by man-made pollution, particularly chlorofluorocarbons (CFCs), which were once emitted by many refrigerators. In recent decades, however, global collaboration has given it a chance to rebuild. The Montreal Protocol (Canada), signed in 1987 and ratified by 195 countries, has greatly reduced the amount of CFCs in the atmosphere and the ozone layer will be allowed to fully recover, according to UN estimates.

Fears surrounding geoengineering

In 2016, the Kigali Agreement also provided for the phasing out of extremely climate-damaging hydrofluorocarbons (HFCs) in refrigerators and air conditioning systems. Experts already estimate that if the agreement is adhered to, it could reduce global warming by 0.5°C by 2100.

However, the latter was also the first to address the potential impact of geoengineering projects on ozone, designed to limit global warming, and warned of their undesirable effects. The idea would be to intentionally add airborne particles in the stratosphere to reflect some of the sun’s rays. One such project would involve injecting a significant amount of sulfur particles into the upper layer of the atmosphere.

These technologies would somehow replicate a volcanic eruption similar to that of Pinatubo in the Philippines in 1991, which lowered the temperature by 1°C. But ozone levels were degraded in the years that followed, notes John Pyle, co-chair of the scientific panel working on ozone for the UN.

Injecting particles into the atmosphere “could lead to a serious drop in ozone levels,” he warns. “There are a lot of uncertainties,” he said.

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The gate of Paris moves away

The planet has warmed by almost 1.2°C since the pre-industrial era, which has already led to increases in heat waves, floods and storms. The international community is committed to limiting this warming to well below 2°C, if possible to 1.5°C. However, current policy points to a temperature increase of 2.8°C by the end of the century, which the United Nations says is well above the limits of the Paris Agreement.

Geoengineering projects are sometimes suggested as a solution to save time, but scientists have already warned of the dangers associated with these technologies. A deliberate change in solar radiation, for example, could disrupt the monsoon regime in South Asia and West Africa, wiping out the crops on which hundreds of millions of people depend, according to published studies.

“The simplest thing is to stop the emission of greenhouse gases”

And if radiation modification stopped, “it is very likely that the surface temperature would rise rapidly,” estimates the IPCC.

Particle injection over Antarctica has been simulated with mixed results. This would certainly lower global temperature by 0.5°C over twenty years, but the hole in the ozone layer would return to near 1990s levels to release greenhouse gases into the atmosphere,” said John Pyle. “And it’s difficult.”