(Paris) The ozone hole could be reduced within four decades, but potential solar geoengineering projects to limit global warming could have undesirable effects, scientists warned on Monday.
Posted at 11:16 am
Marlowe HOOD Agence France Press
“If current guidelines remain in place, the ozone layer should return to 1980 levels. [avant l’apparition du trou] until about 2066 over Antarctica, 2045 over the Arctic and 2040 over the rest of the world,” says the UN Environment in its four-year estimate.
“The elimination of almost 99% of banned ozone-depleting substances has helped preserve the ozone layer and has contributed significantly to its recovery in the upper stratosphere and a reduction in human exposure to harmful ultraviolet (UV) rays from the sun,” the UN notes -mandate experts.
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.
“uncertainties”
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 Mount 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.
proliferation of heat waves
The planet has warmed by almost +1.2°C since the pre-industrial era, which has already led to an increase in heat waves, floods and storms.
The international community is committed to limiting this warming to well below +2°C, if possible +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.
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 the global temperature by 0.5°C over 20 years, but the hole in the ozone layer would return to levels close to those of the 1990s.
“The easiest thing to do is stop the release of greenhouse gases into the atmosphere,” said John Pyle. “And it’s difficult.”