The ozone layer is mainly found in the lower portion of the stratosphere, about 20 to 30 km (12 to 19 miles) above the earth, though the thickness varies seasonally and geographically. The ozone layer protects living things from harmful ultraviolet rays from the sun; without the protection of the ozone layer, millions of people would develop skin cancer and weakened immune systems.
THE OZONE LAYER is a belt of the naturally occurring gas “ozone.” It sits 9.3 to 18.6 miles (15 to 30 kilometers) above Earth, and serves as a shield from the harmful ultraviolet B (UVB) radiation emitted by the sun.
Ozone is a highly reactive molecule that contains three oxygen atoms. It is constantly being formed and broken down in the high atmosphere, 6.2 to 31 miles (10 to 50 kilometers) above Earth, in the region called the stratosphere.
The ozone layer above the Antarctic has been particularly impacted by pollution since the mid-1980s. This region’s low temperatures speed up the conversion of CFCs to chlorine. In the southern spring and summer, when the sun shines for long periods of the day, chlorine reacts with ultraviolet rays, destroying ozone on a massive scale, up to 65 percent. This is what some people erroneously refer to as the “ozone hole.” In other regions, the ozone layer has deteriorated by about 20 percent.
About 90 percent of CFCs currently in the atmosphere were emitted by industrialized countries in the Northern Hemisphere, including the United States and Europe. These countries banned CFCs by 1996, and the amount of chlorine in the atmosphere is falling now. Scientists had estimated it would take another 50 years for chlorine levels to return to their natural levels. In fact, in November 2018, the UN released a report saying that, based on the latest science, the ozone layer is on track to be fully healed within 50 years.
Concern about a depleting ozone layer dates back to the 1970s. Scientists then discovered a “hole” in the ozone layer over the Antarctic in the 1980s. Initially, concern for the ozone focused on chemicals known as chlorofluorocarbons (CFCs). Later, halons, carbon tetrachloride (CTC), methyl bromide and hydro chlorofluorocarbons (HCFCs) were targeted.
In 1985, countries adopted the Vienna Convention for the Protection of the Ozone Layer. Two years later, they adopted the Montreal Protocol on Substances that Deplete the Ozone Layer. This protocol has its own financial mechanism, the Multilateral Fund, which helps developing countries comply with the protocol.
With 197 nations party to the accord, the Montreal Protocol is the only universally ratified treaty in United Nations’ history. To date, it has helped reduce more than 97 percent of all global consumption and production of controlled ozone-depleting substances (ODS). As a result, the levels of these substances in the atmosphere have begun to fall.
The same chemicals that harm the ozone also warm the climate. Between 1989-2013, the Montreal Protocol prevented the emissions of 5.6 billion tonnes CO2 equivalent annually. In 2016, the Parties agreed to regulate hydroflurocarbons (HFCs) under the Montreal Protocol. While HFCs have largely replaced CFC and HCFCs and do not harm the ozone layer, they are powerful greenhouse gases. Controlling the uses of HFCs will effectively prevent a .5 °C increase in global temperature.
The GEF is not formally linked to the Montreal Protocol but actively support its implementation. Under the terms of the protocol, countries with economies in transition were not eligible for multilateral funding. The GEF stepped in to fill the gap. The GEF helps the Russian Federation and nations in Eastern Europe and Central Asia to phase out their use of ozone-destroying chemicals under the terms of the Montreal Protocol.