New Delhi: The 2021 Antarctic ozone hole reached its maximum area on October 7, and has been the 13th largest since 1979, scientists from NASA and the National Oceanic and Atmospheric Administration (NOAA) reported on October 27. 


The 2021 ozone hole developed in a manner similar to last year's. 


Since winter in the Southern Hemisphere is colder than usual this year, the ozone hole is likely to persist till November or early December. 


Paul Newman, chief scientist for Earth sciences at NASA's Goddard Space Flight Center, said the ozone hole "would have been much larger" had there been no Montreal Protocol, NASA mentioned in a statement.


What Is Ozone Hole And How Is It Measured?


The ozone hole is a thinning of the ozone layer in the stratosphere, which is an upper layer of Earth's atmosphere. The ozone layer is depleted due to chemically active forms of chlorine and bromine, derived from refrigerants. .


These active forms initiate ozone-depleting reactions when the Sun rises in the Antarctic at the end of winter.


Satellite instruments aboard Aura, Suomi-NPP (National Polar-orbiting Partnership) and NOAA-20 are used to detect and measure the growth and break up of the ozone hole.


The 2021 ozone hole reached a maximum of 9.6 million square miles, which is roughly the size of North America. It began to shrink in mid-October. 


The reason why the ozone hole is so large this year is that colder than average temperatures and strong winds in the stratosphere are circling Antarctica.


In order to record the ozone layer's thickness, NOAA scientists at the South Pole Station have released weather balloons carrying ozone-measuring instruments called ozonesondes. 


As the balloon rises into the stratosphere, ozonesondes measure the varying ozone concentrations.


Dobson Spectrophotometer is an optical instrument that records the total amount of ozone between the surface and the edge of the space. This is known as the total column ozone value.


The total-column ozone value of 102 Dobson Units recorded on October 7 is the 8th lowest since 1986. Ozone was almost completely absent at altitudes between 8 and 13 miles, during the ozone hole's maximum. 


The Montreal Protocol and subsequent amendments are helping the ozone hole recover. This is because the use of harmful ozone-depleting substances called chlorofluorocarbons has been banned. 


Many ozone holes in the 1990s and early 2000s were significantly larger than the 2021 ozone hole.


This year's ozone hole would have been larger by about 1.5 million square miles, under the same weather conditions, had the atmospheric chlorine levels from CFCs today been as high as they were in the early 2000s.  


Climate Change Should Be Tackled Just Like Ozone Layer: David Attenborough


English broadcaster and historian Sir David Attenborough Thursday called on world leaders meeting for the upcoming COP26 to be held in Glasgow, to listen to science and take action, the same way as they did with the ozone layer in the 1980s, according to reports.


Sir David said, "It was science in the Antarctic which warned the world of the hole in the ozone layer. That was 1985.” 


He said it was remarkable that it only took two years for the world to take notice of the warning that the hole was damaging to our globe, and for the nations to take action. The Montreal Protocol was signed two years after that. The Montreal Protocol phased out chlorofluorocarbons (CFCs) in just two years. Sir David Attenborough expects the nations meeting at COP26 to work at the same speed, and called for "urgent, science-based action" by world leaders.


He added it would be marvellous if the 197 countries of the world, who will participate in climate talks at COP26, join together and actually do something at the UK hosted event. He said he hopes and prays that the nations listen to the science of what must be done to prevent it from being overcome by catastrophe.