The ozone layer that protects from solar radiation is being reconstituted, but some plans to fight climate change that involve launching sulfur into the stratosphere could put that shield in danger, scientists warned this past Monday. The ozone layer, whose “hole” caused alarm in the 1990s, will have been reconstituted in the next 4 decades if it continues on its current trajectory, according to the report by experts from the UN, the United States and the European Union (EU).
The historic agreement signed by almost 200 countries in 1987 in Montreal to eliminate the emission of chlorofluorocarbon aerosols contributed greatly to this radical change. The dispersion of these industrial particles in the atmosphere was endangering that thin layer, essential for the preservation of terrestrial life, located between 11 and 40 kilometers above the planet’s surface. “Ozone is recovering and that is good news”, John Pyle, a professor at Cambridge University and co-responsible for this report, known as the Ozone Depletion Assessment, told AFP.
The ozone layer should recover its normal levels, both in terms of extension and depth, in the Antarctic region (where the hole was most pronounced) by 2066 according to the report, released jointly by the World Meteorological Organization (WMO) and US agencies and European. In the Arctic, full recovery will occur by 2045 and in the rest of the world in about 20 years.
The ozone layer filters out the vast majority of the Sun’s ultraviolet rays, which damage the DNA of living things and can cause cancer. But at the terrestrial level, instead, ozone is one of the main components of air pollution and a cause of respiratory diseases.
Like a volcano
Eliminating these ozone-depleting substances in the stratosphere will reduce the increase in global warming by up to 1 degree Celsius between now and mid-century, compared to the previous situation, in which their use increased by 3% each year, according to the report. Instead, the world is on the wrong track to address the problem on other fronts of climate change, such as CO2 or methane emissions from fossil fuels.
One proposal would be to scatter tiny sulfur particles into the stratosphere. Such stratospheric aerosol injection (SAI) is a phenomenon that the world has witnessed at a natural level, such as the eruption of the Pinatubo volcano in the Philippines in 1991. Millions of tons of dust ejected by the volcano temporarily obscured part of the atmosphere, which contributed to lowering the temperature for a year.
Unexpected consequences
Some scientists estimate that if 8 to 16 million tons of sulfur dioxide were injected into the stratosphere each year, roughly the same amount as emissions from the Pinatubo, the planet’s average temperature would drop by 1°C. But that measure would again reduce the ozone layer to its 1990 levels. It would represent “major ozone depletion”, Pyle warns. And furthermore, these sulfur particles would disturb the monsoons in Africa and Asia, or the rainy cycle in the Amazon, which is already undergoing a process of savannization.
This report on the state of the ozone is the tenth to date, and nevertheless warns that the situation is not good in the lower part of the stratosphere that covers the tropics or more temperate regions. Chlorofluorocarbons (CFCs) have eroded the upper part of the stratosphere, especially over the polar region. But the role of so-called “very short-lived substances” (VSLS), which are not covered by the Montreal Treaty, and climate change still remains to be elucidated.
