The hole in the ozone layer could be reduced within 40 years, according to the United Nations
ALEXANDER GERST/AFP
According to the projections of UN experts, the hole in the ozone layer could be reduced within four decades. This illustration of Earth taken from the International Space Station in August 2018.
ENVIRONMENT – Finally some good news for the future of the planet. The hole in the ozone layer could be reduced within four decades, and the phasing out of chemicals that damage it help limit climate change, according to a report published on Monday January 9 by a group of experts mandated by the UN Environment. Potential solar geoengineering projects could have unintended effects, however, scientists warn.
“The phasing out of nearly 99% of banned substances that deplete the ozone has helped to preserve the ozone layer and contributed significantly to its restoration in the upper stratosphere and reduction of human radiation exposure. harmful ultraviolet (UV) rays from the sun », experts note. If current policies remain in place, the hole in the ozone layer could shrink “roughly 2066 over Antarctica, 2045 over the North Pole and 2040 around the world”, they added.
The hole in the ozone layer was created by man-made pollution, especially by the chlorofluorocarbons (CFCs) that were once emitted by many refrigerators. Over the last few decades, global cooperation, including ratification of the Montreal Protocol by 195 countries – which sharply reduced the use of CFCs – has provided an opportunity for recovery.
There is a lot of uncertainty about geo-engineering projects
In 2016, the Kigali agreement also provided for the phase-out of hydrofluorocarbons (HFCs), a gas that is extremely harmful to the climate and is used in refrigerators and air conditioners. If the agreement is adhered to, it could reduce global warming by 0.5°C by 2100, experts estimate.
However, the latter is also looking at for the first time the potential effects on ozone from a geo-engineering project meant to limit global warming, warning against unintended effects. These projects have the idea of deliberately adding suspended particles in the stratosphere to reflect some of the sunlight. One of them consists in injecting a large number of sulfur particles into the upper atmosphere.
The technology somehow mimics a volcanic eruption similar to that of Pinatubo in the Philippines in 1991, which lowered temperatures by 1°C. But ozone levels were affected in subsequent years, noted John Pyle, co-chair of the scientific panel working on ozone for the United Nations. Injection of particles into the atmosphere “can result in a serious drop in ozone levels”he warned. “There is a lot of uncertainty”according to him.
“The easiest way is to stop passing gas”
The planet has risen by almost +1.2°C since the pre-industrial era, which has led to increased heat waves, floods and storms. The international community is committed to limiting this warming to below +2°C, +1.5°C where possible. But current policies point to a temperature rise of 2.8°C by the end of the century, well above the Paris agreement limit, according to the United Nations.
Geo-engineering projects are sometimes put forward as a time-saving solution, but scientists have warned of the dangers associated with this technology. Deliberate modification of solar radiation could, for example, disrupt the monsoon regimes in South Asia and West Africa and thereby destroy the crops on which hundreds of millions of people depend, according to published studies.
What if radiation modification ends “for some reason it is very likely that the surface temperature will rise rapidly”, estimates the IPCC. Particle injection over Antarctica has been simulated, with mixed results. This would certainly reduce global temperatures by 0.5°C over twenty years, but the hole in the ozone layer would return to levels close to those of the 1990s. “The easiest thing to do is to stop releasing greenhouse gases into the atmosphere”underlined John Pyle. “And it’s hard”.
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