Why the ozone layer is important for us?

The ozone layer is a natural layer of gas in the upper atmosphere which protects humans and other living things from the harmful ultraviolet (UV) rays of the sun.

The main function of the ozone layer is to absorb the Sun's ultraviolet radiation, hence protecting the Earth from its harmful effects.

Thinning of the ozone layer means increased skin related diseases. In recent decades, because of the release of large quantities of man-made organohalogen compounds, especially chlorofluorocarbons (CFCs) and bromofluorocarbons, the ozone layer is depleting. If earth loses the protection of the ozone layer, then life on the planet will be at great risk. If not blocked by the Ozone layer, exposure to ultraviolet radiation can increase the risk of cataracts, skin cancer and other detrimental effects among humans.

The ozone layer acts as a protective shield against all such harmful radiations from the sun. 

The latest Scientific Assessment of Ozone Depletion completed in 2018, shows that, as a result, parts of the ozone layer have recovered at a rate of 1-3% per decade since 2000. At projected rates, Northern Hemisphere and mid-latitude ozone will heal completely by the 2030s. The Southern Hemisphere will follow in the 2050s and Polar Regions by 2060.

When " World Ozone Day" is celebrated?

16 September of every year marked as the World Ozone Day. On 19 December 1994, the United Nations General Assembly proclaimed 16 September the International Day for the Preservation of the Ozone Layer, commemorating the date, in 1987, on which the Montreal Protocol on Substances that Deplete the Ozone Layer was signed. The Montreal Protocol is an international treaty planned to protect the ozone layer by reducing the production of substances that are responsible for ozone layer depletion. The Montreal Protocol phases down the consumption and production of the different ozone-depleting substances (ODS) in a step-wise manner, with different timetables for developed and developing countries. Under this treaty, all parties have specific responsibilities related to the phase-out of the different groups of ODS, control of ODS trade, annual reporting of data, national licensing systems to control ODS imports and exports, and other matters.

This year, we celebrated 35 years of the Vienna Convention and 35 years of global ozone layer protection. Life on Earth would not be possible without sunlight. But the energy emanating from the sun would be too much for life on Earth to thrive were it not for the ozone layer. This stratospheric layer shields Earth from most of the sun’s harmful ultraviolet radiation. Sunlight makes life possible, but the ozone layer makes life as we know it possible. The theme of World Ozone Day 2020 was Ozone for life.

The theme of World Ozone Day 2019 was '32 years and Healing'. This year's theme celebrates three decades of remarkable international cooperation to protect the Ozone Layer and the climate under the Montreal Protocol. It also reminds the people to keep up the momentum to ensure healthy people and a healthy planet.

Where is ozone primarily produced?

Ozone primarily a compound of three oxygen molecules. Most atmospheric ozone is concentrated in a layer in the stratosphere, about 9 to 18 miles (15 to 30 km) above the Earth's surface. At any given time, ozone molecules are constantly formed and destroyed in the stratosphere. The total amount has remained relatively stable during the decades that it has been measured. In the first step, solar ultraviolet radiation breaks apart one oxygen molecule (O2) to produce two oxygen atoms (2O).

      But a few decades ago it was observed that the ozone layer started depleting due to human behaviour. And the main reason for depletion was the common use of chlorofluorocarbon (CFC) gases. At the time, CFCs were commonly used in aerosol sprays and as coolants in many refrigerators. As they reach the stratosphere, the sun's UV rays break CFCs down into substances that include chlorine.

      One atom of chlorine can destroy more than 100,000 ozone molecules, according to the U.S. Environmental Protection Agency, eradicating ozone much more quickly than it can be replaced. And then in 1987 Montreal Protocol on Substances That Deplete the Ozone Layer began the phaseout of CFCs in 1993 and sought to achieve a 50 per cent reduction in global consumption from 1986 levels by 1998. By 2005 the consumption of ozone-depleting chemicals controlled by the agreement had fallen by 90–95 per cent in the countries that were parties to the protocol.

      Scientists in 2014 observed a small increase in stratospheric ozone—the first, they thought, in more than 20 years—which they attributed to worldwide compliance with international treaties regarding the phaseout of ozone-depleting chemicals and upper stratospheric cooling because of increased carbon dioxide. Upon a more thorough study, however, scientists in 2016 announced that stratospheric ozone concentrations had been increasing in the upper stratosphere since 2000 while the size of the Antarctic ozone hole had been decreasing. And yes, now the ozone layer recovering.

Who discovered the ozone layer and ozone depletion?

The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 15 kilometres (9.3 to 21.7 mi) above Earth, although its thickness varies seasonally and geographically.

The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson.

In how many layers our atmosphere divided?

The atmospheric layers divided into five

• The Troposphere: This is the lowest part of the atmosphere - the part we live in. It contains most of our weather - clouds, rain, snow. In this part of the atmosphere, the temperature gets colder as the distance above the earth increases, by about 6.5°C per kilometre. The actual change of temperature with height varies from day to day, depending on the weather. The troposphere contains about 75% of all of the air in the atmosphere and almost all of the water vapour (which forms clouds and rain). The decrease in temperature with height is a result of the decreasing pressure. If a parcel of air moves upwards it expands (because of the lower pressure). When air expands it cools. So air higher up is cooler than air lower down.
• The Stratosphere: This extends upwards from the tropopause to about 50 km. It contains much of the ozone in the atmosphere. The increase in temperature with height occurs because of the absorption of ultraviolet (UV) radiation from the sun by this ozone. Temperatures in the stratosphere are highest over the summer pole and lowest over the winter pole. By absorbing dangerous UV radiation, the ozone in the stratosphere protects us from skin cancer and other health damage. However, chemicals (called CFCs or freons, and halons) which were once used in refrigerators, spray cans and fire extinguishers have reduced the amount of ozone in the stratosphere, particularly at polar latitudes, leading to the so-called "Antarctic ozone hole".
• The Mesosphere: The region above the stratosphere is called the mesosphere. Here the temperature again decreases with height, reaching a minimum of about -90°C at the "mesopause".
• The Thermosphere and Ionosphere: The thermosphere lies above the mesopause, and is a region in which temperatures again increase with height. This temperature increase is caused by the absorption of energetic ultraviolet and X-Ray radiation from the sun.
• The Exosphere: The region above about 500 km is called the exosphere. It contains mainly oxygen and hydrogen atoms, but there are so few of them that they rarely collide - they follow "ballistic" trajectories under the influence of gravity, and some of them escape right out into space.