adminZimbabwe joined the rest of the world in commemorating the International Day for the Preservation of the Ozone Layer.
This day is commemorated on September 16 every year globally. The day marks the signing of the Montreal Protocol which was signed on that day in 1987 by a number of countries that were apprehensive about the depletion of the ozone layer.
World Ozone Day provides an opportunity to reflect on the progress that has been made towards the protection of the ozone layer and it serves as a reminder to decision-makers and the general public, of the need to protect this valuable shield that safeguards the earth and in the long-run, our lives.
This year, the Ministry of Environment, Water and Climate commemorated this day in Kwekwe under the theme “A Healthy Atmosphere — The Future We Want”.
Here are some of the questions often asked about the ozone layer.
What is ozone and where is it?
Ozone is a gas that is naturally present in our atmosphere. It is found primarily in two regions of the atmosphere.
About 10 percent of the atmospheric ozone is in the troposphere, the region closest to the earth. The remaining ozone (about 90 percent) is in the stratosphere between the top of the troposphere. The large amount of ozone in the stratosphere is often referred to as the “ozone layer”.
How is the ozone formed?
Ozone is formed throughout the atmosphere in a chemical process which involves the oxygen molecules being broken down by the ultraviolet rays from the sun. In the lower atmosphere (troposphere) ozone is formed by different set of chemicals that involve naturally occurring gases.
Why do we care?
Ozone in the stratosphere absorbs a large part of the sun’s biologically harmful ultraviolet radiation.
Stratospheric ozone is considered “good” ozone because of this beneficial role. In contrast, ozone formed at the earth’s surface in excess of natural amounts is considered “bad” ozone because it is harmful to humans, plants and animals. Natural ozone near the surface and in the lower atmosphere plays an important beneficial role in chemically removing pollutants from the atmosphere.
Depletion of the ozone layer has some of the following effects :
- Skin cancer — linked to chronic sun exposure in fair-skinned people
- Risk of breast and prostate cancer
- Eye cataracts — snow and permanent blindness,
- Suppression of the immune system
- Sunburn and photo ageing of the skin.
- Reduction in yields and crop quality
Ozone distribution over the globe
The distribution of ozone over the earth varies with location and time-scales that range from daily to seasonal.
The variations are caused by large scale movements of stratospheric air and the chemical production and destruction of ozone, total ozone is generally lowest at the equator and highest at the polar regions.
How is ozone measured?
The amount of ozone in the atmosphere is measures by instruments on the ground and carried aloft on balloons, aircraft and satellites. Some instruments measure the ozone locally by continuously drawing air samples into a small detection chamber.
Other instruments measure ozone over long distances by using ozone’s unique optical absorption or emission properties.
What emissions lead to ozone depletion?
Certain industrial processes and consumer products result in the emission of ozone depleting substances to the atmosphere.
ODSs are manufactured halogen source gases that are controlled worldwide by the Montreal Protocol. These gases bring chlorine and bromine atoms to the stratosphere, where they destroy ozone in chemical reactions. Important examples are the chlorofluorocarbons, once used in all refrigeration and air conditioning systems.
These are also contained in aerosol propellants, in cosmetic and medical sprays, solvents, including metal cleaning, dry cleaning, soil fumigation, commodities and building disinfection.
Are there regulations?
Yes, the production and consumption of ozone depleting substances are controlled under a 1987 international agreement known as the “Montreal Protocol on Substances that Deplete the Ozone layer” and by its subsequent Amendment and Adjustments.
The Protocol, now ratified by all 197 United Nations member states, establishes legally binding controls on national production and consumption of ozone depleting substances.
Success of Montreal Protocol
Yes, as a result of the Montreal Protocol, the overall abundance of the ozone depleting substances in the atmosphere has been decreasing for about a decade.
If the nations of the world continue to comply with the provisions of the Montreal Protocol, the decrease will continue throughout the 21st century.
Those gases that are still increasing in the atmosphere, such as halon-1301 and HCFC-22, will begin to decrease in the coming decades if compliance with the Protocol continues. Only after mid-century will the effective abundance of ODS fall to values that were present before the Antarctic ozone hole observed in the early 1980s.
Ozone layer cause climate change?
No, ozone depletion itself is not the principal cause of climate change. Changes in the ozone and the climate are directly linked because ozone absorbs solar radiation and is also a greenhouse gas.
Stratospheric ozone depletion and increases in global tropospheric ozone that have occurred in the recent decades have opposing contributions to climate change.
The ozone depletion contribution, while leading to surface cooling, is small compared with the contribution from all other greenhouse gas increase, which leads to surface warming. The total forcing from these other greenhouse gases is the principle cause of observed and projected climate change.
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