From UPSC perspective, the following things are important :
Prelims level : Ozone Hole
Mains level : Climate change impact
The Antarctic ozone hole — one of the deepest, largest gap in the ozone layer in the last 40 years — has closed, according to the World Meteorological Organization (WMO).
Try this PYQ:
Q.Consider the following statements:
Chlorofluorocarbons, known as ozone-depleting substances are used:
- In the production of plastic foams
- In the production of tubeless tyres
- In cleaning certain electronic components
- As pressurizing agents in aerosol cans
Which of the statements given above is/are correct?
(a) 1, 2 and 3 only
(b) 4 only
(c) 1, 3 and 4 only
(d) 1, 2, 3 and 4
Antarctic Ozone Hole
- The Antarctic “ozone hole” was discovered by British Antarctic Survey scientists Farman, Gardiner and Shanklin in 1985.
- It came as a shock to the scientific community because the observed decline in polar ozone was far larger than anyone had anticipated.
- It was caused by the chemical reactions on polar stratospheric clouds (PSCs) in the cold Antarctic stratosphere caused a massive.
- Though localized and seasonal, an increase in the amount of chlorine present in active, ozone-destroying forms.
Role of PSCs
- The polar stratospheric clouds in Antarctica are only formed when there are very low temperatures, as low as −80 °C, and early spring conditions.
- In such conditions, the ice crystals of the cloud provide a suitable surface for the conversion of unreactive chlorine compounds into reactive chlorine compounds, which can deplete ozone easily.
An annual process
- An ozone hole is the thinning of the ozone layer boosted in size by colder temperatures.
- The formation of the ozone hole in the Antarctic has been an annual occurrence and has been recorded for the last 40 years.
- Human-made chemicals migrate into the stratosphere and accumulate inside the polar vortex. It begins to shrink in size as warmer temperatures dominate.
- As the temperatures high up in the stratosphere start to rise, ozone depletion slows, the polar vortex weakens and breaks down.
- By the end of December, ozone levels return to normal.
The hole closes after achieving peak
- The annually occurring ozone hole over the Antarctic had rapidly grown from mid-August and peaked at around 24 million square kilometres — one of the largest so far — in early October 2020.
- The expansion of the hole was driven by a strong, stable and cold polar vortex and very cold temperatures in the stratosphere.
- The same meteorological factors also contributed to the record 2020 Arctic ozone hole, which has also closed.
Note: A polar vortex is a wide expanse of swirling cold air, a low-pressure area, in Polar Regions. During winters, the polar vortex at the North Pole expands, sending cold air southward.