A few days ago, the United Nations agency released a new study saying that the Earth’s ozone layer is expected to be repaired within the next 40 years. Some commentators believe that the restoration of the Earth’s ozone layer will set a good precedent for global climate action.
For decades, the Earth’s ozone layer, which protects life on Earth from the sun’s harmful ultraviolet (UV) rays, has been hit by a variety of common chemicals, from refrigerants to hairspray. But now the hole in the ozone layer is diminishing thanks to decades of global efforts to repair it, the World Meteorological Organization (WMO) confirmed recently.
Scientists first discovered a large hole in the Antarctic in 1985. A few years later, the world adopted the Montreal Protocol, a global environmental convention to phase out “ozone-depleting substances.
Now, thanks to this work, scientists expect the ozone layer to start looking more normal and healthy in the coming decades. This reduces people’s risk of skin cancer and cataracts, as well as sun damage to plants and crops.
Some studies show that for every 1 percent reduction in the ozone content of the atmosphere, the amount of ultraviolet radiation from the sun at ground level increases by 2 percent, and the number of people with skin cancer increases by 5 to 7 percent, as well as the number of people with cataracts and respiratory diseases; if the ozone content of the ozone layer decreases by 10 percent, the amount of ultraviolet radiation in different areas of the ground increases by 19 to 22 percent, and the incidence of skin cancer increases by 15 to 25 percent as a result If the ozone layer is reduced by 10%, UV radiation will increase by 19% to 22% in different areas of the ground, and the incidence of skin cancer will increase by 15% to 25%.
- Ozone layer recovery is on the right track
The United Nations expert panel presented its findings at the annual meeting of the American Meteorological Society. The report released by the panel said that since 2000, the area and depth of the hole in the ozone layer over the Antarctic have been gradually improving.
If countries continue to pursue current policies, the ozone layer over much of the globe is expected to recover to 1980 levels by 2040. However, the recovery of the ozone layer over polar regions will take longer, with the Arctic expected to be there by 2045 and the Antarctic by 2066. Of course, this progress depends on the development of policies to limit these ozone-depleting substances.
Ozone molecules in the stratosphere absorb harmful UV-B radiation from the sun and prevent most of the ultraviolet light from reaching them. This is part of a process that is constantly producing and destroying ozone in the atmosphere. But when certain chemicals drift there, that balance is upset — causing more ozone to be destroyed than is produced.
According to Dr. David Fahey, co-chair of the panel, “The recovery of the ozone layer is on track, and the peak of global ozone destruction is a thing of the past because all countries have adopted effective control measures under the Montreal Protocol.”
Last October, NASA and the National Oceanic and Atmospheric Administration released research that concluded that the ozone layer hole over Antarctica was 23.2 million square kilometers, a “slight decrease” from the previous year. Overall, the hole has tended to shrink in recent years. At the time, the National Oceanic and Atmospheric Administration predicted that the hole in the ozone layer over Antarctica would recover around 2070.
In the mid-1980s, researchers found that the concentration of the ozone layer over Antarctica had declined significantly. Nearly 95 percent of the ozone was destroyed in the center of the ozone layer over the poles. When observed from the ground upwards, the ozone layer at high altitudes was so thin that it appeared to form a “hole” thousands of kilometers in diameter compared to the surrounding area, hence the name “ozone hole”. It was this discovery that triggered the international community to urgently repair the ozone layer.
- The most effective global environmental conventions
The formation and expansion of the ozone hole have both natural and man-made causes. Ozone itself is a chemically very unstable substance, easily decomposed into oxygen molecules and oxygen atoms by chemical reactions. The chlorofluorocarbons (CFCs) in products such as foaming agents, fire extinguishers, pesticides and refrigerants, which were used in large quantities by human beings, are the “culprits” for the above chemical reaction of ozone.
To date, the environmental problem of ozone layer depletion seems to be effectively addressed, with more than 100 ozone-depleting compounds finally banned and phased out, including a 99% reduction in the use of chlorofluorocarbons (CFCs).
The global agreement to protect the ozone layer also facilitates efforts to mitigate climate change. The ozone-depleting substances were replaced by another class of chemicals that happen to be potent greenhouse gases, called hydrofluorocarbons (HFCs).
In 2016, the international community also adopted the Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer, which also places restrictions on the use of Freon substitutes, taking into account not only the damage to the ozone layer but also the greenhouse gas emissions they cause.
Experts estimate that if the amendment is complied with, by 2100, it is expected to reduce the Earth’s warming by 0.3°C to 0.5°C over that period. For context, the world has warmed by about 1.2 degrees Celsius since the pre-industrial era, which has exacerbated many of the extreme weather disasters we live with today.
But WMO’s good news also comes with a climate warning. The panel of experts warned that “geoengineering” – the deliberate manipulation of the climate or atmosphere to eliminate some of the damage we cause by burning fossil fuels – could be damaging to the ozone layer. They are particularly concerned about a strategy called stratospheric aerosol injection (SAI).
Proponents argue that this strategy could help cool the Earth because aerosols may reflect some sunlight back into space. But according to a recent WMO-backed report, SAI “poses significant risks and could lead to unintended consequences. Some climate experts have sounded the alarm over a startup’s recent attempt to release reflective sulfur particles in the stratosphere.
However, the phase-out of ozone-depleting chemicals is seen as an example of what can be achieved when people work together to address the global environmental crisis. “OzonAction has set a precedent for climate action. Our success in phasing out ozone-depleting chemicals shows us what we can do and must do. As a matter of urgency, we must move away from fossil fuels and reduce greenhouse gases, thereby limiting temperature rise. ” said WMO Secretary-General Petteri Taalas in a statement.
Because of its good results, the Montreal Protocol is considered the most effective global environmental convention ever. Over the past 35 years, the Montreal Protocol has become a true champion of the environment, the United Nations Environment Programme said.
This article is from WeChat: New Research (ID: chuxinyanjiu), written by Justine Calma and compiled by Tang Shi