The Antarctic hole was unprecedented as the polar vortex kept the temperature of the ozone layer cold, preventing the mixing of ozone depleted air above Antarctica with ozone rich air from higher latitudes. Since the ban on halocarbons, the ozone layer has slowly been recovering, according to WMO. We are a voice to you; you have been a support to us.
Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together. Last year's hole also began unexceptionally in September, but then turned into "one of the longest-lasting ozone holes in our data record," according to Copernicus.
The ozone layer , which sits between 9 and 22 miles above the Earth, protects the planet from ultraviolet radiation. The hole in the Southern Hemisphere is typically caused by chemicals, such as chlorine and bromine migrating into the stratosphere, creating catalytic reactions during Antarctic winter. The ozone hole is related to the Antarctic polar vortex, a band of swirling cold air that moves around the Earth.
This method has been used to measure the ozone layer at Halley Research Station since In , British Antarctic Survey scientists published results showing a steep decline in the levels of ozone over Halley since the s, particularly during the austral spring, and the existence of the ozone hole was revealed.
Since then, the extent of the ozone hole has been monitored continuously using both ground-based and satellite-based techniques. The image from the link above shows the size and shape of the ozone hole as measured in October Notice that the hole where values are only around Dobson units covers most of Antarctica, and areas of depleted ozone under units extend beyond the continent. The ozone hole has developed because people have polluted the atmosphere with chemicals containing chlorine and bromine.
The primary chemicals involved are chlorofluorocarbons CFCs for short , halons, and carbon tetrachloride. CFCs in particular have been used for a wide range of applications, including refrigeration, air conditioning, foam packaging, and making aerosol spray cans.
Because these chemicals are so inert, they are able to stay in the atmosphere long enough to be carried upwards to the stratosphere where they can damage the ozone layer. The actual processes by which CFCs and other ozone depleting chemicals destroy ozone are complex and require certain weather conditions to exist. A simplified description of the process involving CFCs is as follows:. The fact that most of the ozone depletion happens over Antarctica also requires some explanation.
CFCs and other ozone depleting gases may come from anywhere, but it is in the south polar stratosphere where the conditions become most favourable for ozone destruction. The key factor is the presence of stratospheric clouds and the lack of atmospheric mixing between the south polar latitudes and air from elsewhere during the austral winter and early spring.
Normally there are no clouds in the stratosphere because there is so little water vapour present. As long as it remains dark, nothing happens; but when spring arrives, UV radiation from the Sun reaches the Antarctic Circle and starts the process of chlorine release and ozone destruction. This continues until the stratospheric clouds disappear due to warming of the south polar atmosphere as summer approaches.
By summertime, stratospheric air from lower latitudes is able to penetrate the polar latitudes, and thereby replenish the ozone layer above Antarctica. Hence, there is a seasonal cycle to the ozone hole over Antarctica with the lowest ozone levels recorded in late September and early October. The ozone layer protects life from harmful UV-B radiation which can cause cancer and stunt the growth of plants. As UV radiation can penetrate into the surface of the ocean, marine organisms especially phytoplankton can also be damaged.
If there was no ozone layer at all, photosynthesis by plants would be impaired and ecosystems could not function as they do today — so it is clearly in our interest to make sure we do not damage the ozone layer. In an historic international agreement was signed the Montreal Protocol which came into force in and set deadlines for reducing and eliminating the production and use of ozone depleting substances.
It also promotes research and development into finding ozone safe substitute chemicals for the uses to which CFCs, etc. It has since been ratified by countries, has been revised several times, and has been described as one of the most successful international treaties. Montreal Protocol The Montreal Protocol on Substances that Deplete the Ozone Layer is the landmark multilateral environmental agreement that regulates the production and consumption of nearly chemicals referred to as ozone depleting substances ODS.
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