According to the observation report of the United Nations, the earth's ozone layer is gradually recovering.
The four-year assessment of the ozone layer status shows that global reduction in the use of chemical sprays to promote ozone layer recovery has achieved significant results. Since 2000, the ozone layer has been recovering at a rate of 1% to 3% per decade, and if the current recovery rate is maintained, the ozone layer over the northern hemisphere and mid-latitude areas will be fully restored by 2030.
, and the ozone layer in the southern hemisphere and polar regions destroys more severely, and it will take longer to recover, but it will also be fully restored around 2050 and 2060 respectively.
The Guardian described this result as a "a victory for global government collaboration." The problem of
ozone layer began to attract the attention of scholars in the late 1970s. At that time, some studies found that the ozone content in the earth's ozone layer was decreasing at a rate of 4%. By 1985, relevant research confirmed that human activities - the discharge of large amounts of ozone-depleting substances (ODS, the main component is fluorocarbon compounds) in the production of chemical preparations such as industrial sprays and refrigerants - have caused damage to the ozone layer over Antarctica and ozone layer hollows have appeared. Most ozone in the atmosphere of
is distributed at a height of 20 to 25 kilometers. At this altitude, ultraviolet radiation can combine oxygen molecules with oxygen atoms into ozone, and can also decompose ozone into oxygen. In the natural environment, the circulating reaction of oxygen and ozone will tend to be in an equilibrium state, but the fluorochlorocarbon compounds produced by human activities will destroy this equilibrium: the compounds decompose fluorine and chlorine under the action of ultraviolet rays, which catalyze the decomposition of ozone, causing the ozone in the circulating reaction to reduce the equilibrium and thus destroy the ozone layer.
In 1987, in order to alleviate the deterioration of the ozone layer, the United Nations drafted the Montreal Protocol on Substances that Deplete the Ozone Layer, which curbs the damage to the ozone layer by restricting the use of HCBCs in countries around the world.
After the Montreal Agreement officially came into effect in 1989, countries around the world began to restrict the use of related chemical preparations and promoted research to seek alternatives to chemical preparations such as Freon . After reducing the use of chemical preparations, the fluorine and chlorine in the atmosphere begin to decrease, and the circulating reaction between oxygen and ozone gradually returns to equilibrium. In the mid-1990s, the ozone content in the ozone layer began to stabilize. Since 2000, as human destruction of the ozone layer decreased, the self-healing function of the atmosphere began to work, and the ozone layer gradually healed itself.
In response to this, the Administrator of the United Nations Environment Programme stated that the Montreal Agreement is "one of the most successful multilateral agreements in history" and believed that the Kigali Amendment to the Agreement will continue to take action for climate change in the future in the context of authoritative scientific support and global cooperation.
" Kigali Amendment" is the 8th and most recent amendment of the Montreal Agreement. In 2016, the 28th Montreal Agreement Conference was held in Kigali, the capital of Rwanda, , and the amendment was adopted at the meeting and will take effect in 2019. The Kigali Amendment aims to further limit the use of hydrofluorocarbon gases, which are still widely used in refrigerant production, and at the same time, the greenhouse effect it causes is tens of thousands of times that of carbon dioxide.
In order to cope with the current severe climate situation, the Kigali Amendment not only takes into account the issue of ozone layer recovery, but also takes into account the restrictions on greenhouse gas emissions. UN research believes that if the amendment is fully implemented, it will reduce the increase in global heating by about 0.5 degrees Celsius this century. This will be of great significance to alleviating the greenhouse effect.
But there are also voices that people are too optimistic about the future of the ozone layer. Brian Toon of the University of Colorado believes that there are still holes in the ozone layer that have not yet been restored, and the long road to the ozone layer has just begun. According to investigation reports, there are still factories in China that are emitting HCFCs and gas, and their emissions reach 13,000 metric tons per year.Most of these companies use cheaper raw materials under economic pressure, resulting in large-scale emissions of HCFCs. Some companies have not been told that emissions of HCFC gases are illegal.
But no matter what, judging from the achievements of decades of ozone treatment, humans can still cheer for themselves.
title picture from: GlobalChange
