Shulou(Shulou.com)11/24 Report--

"humans have managed to reverse the clock of ozone destruction.

A few days ago, relevant United Nations agencies released the latest research report that the earth's ozone layer is expected to be repaired in the next 40 years. It has been commented 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 rays (UV), has been hit by a variety of common chemicals, from refrigerants to hairspray. But now the hole in the ozone layer is decreasing, thanks to decades of global efforts to repair the ozone layer, the World Meteorological Organization (WMO) confirmed.

Scientists first discovered a large hole over Antarctica in 1985. A few years later, countries around the world adopted the Montreal Protocol, a global environmental convention to phase out ODS.

Now, as a result of this work, scientists expect the ozone layer to begin to look more normal and healthier in the coming decades. This reduces the risk of skin cancer and cataracts, as well as the damage of sunlight to plants and crops.

Studies have shown that for every 1% reduction in ozone content in the atmosphere, the amount of ultraviolet radiation from the sun on the ground increases by 2%, the number of people suffering from skin cancer will increase by 5% to 7%, and the number of people suffering from cataracts and respiratory diseases will also increase; if the ozone content in the ozone layer is reduced by 10%, ultraviolet radiation in different areas of the ground will increase by 19%, 22%, and the incidence of skin cancer will increase by 15% and 25%.

01. Recovery of the ozone layer is on the right track

The United Nations panel of experts presented its findings at the annual meeting of the American Meteorological Society. According to the report released by the expert group, the area and depth of the ozone hole over Antarctica have been gradually improving since 2000.

If countries continue to pursue current policies, it is expected that by 2040, the ozone layer over most parts of the world will return to the level of 1980. However, the recovery of the ozone layer over the polar regions will take longer, with the Arctic expected to be 2045 and the South Pole 2066. Of course, this progress depends on the development of policies to limit these ODS.

Ozone molecules in the stratosphere absorb harmful UV-B radiation from the sun, preventing most ultraviolet rays from arriving. This is part of the process of continuous production and destruction of ozone in the atmosphere. But when certain chemicals float there, the balance is broken-causing more ozone to be destroyed than produced.

Dr David FACHE, co-chairman of the expert group, said that "the recovery of the ozone layer is on the right track and the peak of global ozone layer destruction is a thing of the past as all countries have adopted effective control measures under the Montreal Protocol."

In October last year, a study released by NASA and the National Oceanic and Atmospheric Administration concluded that the area of the ozone hole over Antarctica was 23.2 million square kilometers, "slightly smaller" than the year before. On the whole, the void area has shown a shrinking trend 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 a significant decline in the concentration of the ozone layer over Antarctica. In the heart of the ozone layer over the polar regions, nearly 95% of the ozone has been destroyed. Looking up from the ground, the ozone layer in the upper air is so thin that it seems to have formed a "hole" with a diameter of thousands of kilometers, hence the name "ozone hole". It is this discovery that triggered the emergency repair of the ozone layer by the international community.

02. The most effective global environmental convention

There are both natural and man-made reasons for the formation and expansion of the ozone hole. Ozone itself is a substance with very unstable chemical properties, which is easy to be chemically decomposed into oxygen molecules and oxygen atoms. The chlorofluorocarbons in products such as foaming agents, fire extinguishing agents, pesticides and refrigerants that have been widely used by human beings are the "culprits" that promote the above-mentioned chemical reactions in ozone.

So far, the environmental problem of ozone layer destruction seems to be being effectively addressed, with more than 100 ozone-depleting compounds eventually banned and phased out, of which the use of chlorofluorocarbons (CFCs) has been reduced by 99 per cent.

A global agreement to protect the ozone layer also contributes to climate change mitigation efforts. Substances that deplete the ozone layer are replaced by another class of chemicals that happen to be potent greenhouse gases, called hydrofluorocarbons (or HFCs).

In 2016, the international community adopted the Kigali Amendment to the Montreal Protocol on substances that deplete the Ozone layer, which also restricted the use of Freon alternatives, taking into account not only the destruction of the ozone layer, but also greenhouse gas emissions.

Experts estimate that if the amendment is complied with, it is expected to reduce Earth's warming by 0.3 ℃ to 0.5 ℃ during this period by 2100. In terms of background, the world has warmed by about 1.2 degrees Celsius since the pre-industrial era, exacerbating many of the extreme weather disasters we live in today.

But WMO's good news comes with a climate warning. The Panel warns that "geoengineering"-the deliberate manipulation of the climate or atmosphere to eliminate some of the damage we cause by burning fossil fuels could damage the ozone layer. They paid particular attention to a strategy called stratospheric aerosol injection (SAI).

Proponents say this strategy could help cool the planet because aerosols may reflect some sunlight back into space. But according to a recent report backed by WMO, SAI "poses significant risks and may lead to unintended consequences". Some climate experts have sounded the alarm about a start-up'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 in a joint response to the global environmental crisis. " Ozone action has set a precedent for climate action. Our success in phasing out ozone-depleting chemicals shows us what we can and must do. As a matter of urgency, we must get rid of fossil fuels and reduce greenhouse gases, thereby limiting the rise in temperatures. " WMO Secretary General Petteri Taalas said in a statement.

Because of its good effect, the Montreal Protocol is considered to be the most effective global environmental convention in history. The United Nations Environment Programme says the Montreal Protocol has become a true environmental defender in the past 35 years.

This article comes from the official account of Wechat: new Research (ID:chuxinyanjiu), author: Justine Calma, compiled by Tang Poetry

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