Ozone Layer Depletion

Humans have made progress in preventing harm to the ozone layer for the last 30 years by limiting the use of certain chemicals. However, there is still work to be done to maintain and restore the stratosphere, which is located 9 to 18 miles (15 to 30 kilometers) above the Earth's surface.

The sun's ultraviolet (UV) light, notably the dangerous UVB-type rays, is absorbed by atmospheric ozone. UVB radiation has been linked to an increased risk of skin cancer and cataracts, as well as environmental damage to plants and marine habitats. Because of its protective role, atmospheric ozone is sometimes referred to as "good" ozone. This is not to be confused with tropospheric, or ground-level, "bad" ozone, which is a major component of air pollution and has been related to respiratory disease.

Ozone (O3) is a highly reactive gas with three oxygen atoms in each molecule. Its concentration in the atmosphere varies with the seasons and latitudes, although it remained rather constant until worldwide observations began in 1957. In the 1970s and 1980s, groundbreaking research indicated symptoms of disaster.

Threats to the ozone layer and 'the hole'

Mario Molina and Sherwood Rowland, two chemists from the University of California, Irvine, wrote an article in Nature in 1974 explaining the hazards of chlorofluorocarbon (CFC) gases to the ozone layer. CFCs were widely employed as aerosol sprays and as coolants in many refrigerators at the time. CFCs are broken down into chlorine-containing compounds as they reach the stratosphere by the sun's UV rays.

The revolutionary research revealed that the atmosphere has a "limited capacity for absorbing chlorine" atoms in the stratosphere, for which they were awarded the Nobel Prize in Chemistry in 1995.

According to the US Environmental Protection Agency, one atom of chlorine can destroy more than 100,000 ozone molecules, destroying ozone considerably faster than it can be restored.

In 1985, a team of English scientists discovered a hole in the ozone layer above Antarctica that was eventually connected to CFCs, putting Molina and Rowland's work to the test. Every year around the start of the Southern Hemisphere spring, the "hole" is actually an area of the stratosphere with unusually low ozone concentrations (August to October). Spring provides sunshine, which causes chlorine to be released into the stratosphere's clouds.

The current condition of the ozone layer

The Montreal Protocol on Compounds That Deplete the Ozone Layer was signed in 1987 as a landmark agreement to phase out CFCs and other ozone-depleting substances. It has been accepted by all 197 UN member countries. Without the agreement, there would have been an additional 280 million cases of skin cancer, 1.5 million deaths from skin cancer, and 45 million cataracts in the United States, and the world would have been at least 25% hotter.

NASA scientists have discovered the first clear indication that Antarctic ozone is recovering as a result of the CFC phase-down, more than 30 years after the Montreal Protocol: ozone layer depletion in the region has decreased 20% since 2005. And, at the end of 2018, the United Nations reaffirmed in a scientific assessment that the ozone layer is rebounding, predicting that it will be fully recovered in the (non-polar) Northern Hemisphere by the 2030s, the Southern Hemisphere in the 2050s, and polar regions in the 2060s.

The ozone layer is still being monitored, and it appears that recovery may not be as simple as planned. In early 2018, a research indicated that ozone levels in the lower stratosphere have declined abruptly and unpredictably since 1998, while another identified likely continuous violations of the Montreal Protocol.

When it comes to dangerous gases produced by coolants, the world is still in the dark. Some transitional alternatives for hydrochlorofluorocarbons (HCFCs), which are less hazardous but still destructive to ozone, are still in use. The Montreal Protocol's Multilateral Fund can help developing countries eradicate the most extensively used of these, the refrigerant R-22. Hydrofluorocarbons (HFCs), the next generation of coolants, do not destroy ozone, but they are potent greenhouse gases that trap heat and contribute to climate change.

Despite the fact that HFCs account for a minor percentage of emissions compared to carbon dioxide and other greenhouse gases, their warming influence spurred the Kigali Amendment to the Montreal Protocol in 2016. The amendment, which took effect in January 2019, intends to reduce HFC consumption by more than 80% over the next three decades. Meanwhile, corporations and scientists are developing environmentally friendly alternatives, such as new coolants and technologies that decrease or eliminate chemical dependency.

Research has shown that the very phenomenon that gives birth to the Aurora Borealis also, in turn, causes mesospheric ozone layer depletion. (AFP PHOTO /NASA/HANDOUT)


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