An “ozone hole”, which builds up over the Antarctic region this time of the year, has been found to be the smallest since it was first discovered in the 1980s. This comes just a month after the UN Environment Programme said that the ozone layer was on track to be completely restored within “our lifetime” itself.

Depletion of the ozone layer, which protects the planet from the harmful ultraviolet rays of the sun, was considered as grave a threat to the planet in the 1980s and 1990s as climate change is now. Over the years, however, that threat has largely dissipated, as the world has banned the production and consumption of most of the “ozone-depleting substances”. However, it will take another 15-45 years for the ozone layer to be fully restored.

Why is ozone important?

Ozone (chemically, a molecule of three oxygen atoms) is found mainly in the upper atmosphere, an area called stratosphere, between 10 and 50 km from the earth’s surface. Though it is talked of as a layer, ozone is present in the atmosphere in rather low concentrations. Even at places where this layer is thickest, there are not more than a few molecules of ozone for every million air molecules.

But they perform a very important function. By absorbing the harmful ultraviolet radiations from the sun, the ozone molecules eliminate a big threat to life forms on earth. UV rays can cause skin cancer and other diseases and deformities, in plants and animals.

During experiments in Antarctica in the early 1980s, scientists noticed that during September-November, the concentration of ozone fell considerably lower to what was recorded in the 1950s. Studies and satellite measurements confirmed the depletion, and by mid-1980s scientists narrowed down on a class of industrial chemicals like chloroflurocarbons, or CFCs, as the likely culprits.

What causes the ozone hole?

The ‘ozone hole’ is not really a hole. It is a region in the stratosphere, directly above Antarctica, where the concentration of ozone has been measured to become extremely low in certain months. Depletion is not limited to that area and has happened in other regions of the stratosphere as well, but a set of special meteorological and chemical conditions that arise over the Antarctica in the months of September, October and November make the problem much more acute there.

NASA recently reported that this ozone hole, which usually grows to about 20 million sq km in September, was less than half that size this year, the smallest it has ever been during this time after being discovered.

Is this a major gain?

NASA said that this could have happened because of an extraordinarily high temperatures in the stratosphere this year, rather than the ongoing human efforts to contain the ozone depletion. Scientists have reported that temperatures in some areas of the stratosphere — usually over 100 degrees below zero — were 30° to 40°C higher than normal in September this year. At least two such extraordinary warming of the stratosphere has been observed in the past, and on both those occasions the ozone hole was also measured to be smaller than usual. But scientists are not sure why this warming happens. This warming has no observed connection with the warming in lower atmosphere that leads to climate change.

But while this gain might be temporary, the depletion in the ozone layer is consistently being contained, thanks to global efforts to ban the use of harmful chemicals that destroy ozone. CFCs and similar chemicals were being widely used industrial applications like refrigeration, air-conditioning, foams, fire-extinguishers and solvents.

A 1989 global agreement, called Montreal Protocol, organised international consensus on phased elimination of these chemicals. In subsequent years, the agreement has ensured the phase-out of over 90 per cent of these chemicals. Two years ago, an amendment to the Montreal Protocol cleared the way for a faster elimination of another set of similar compounds, called hydroflurocarbons, or HFCs, which were being used as temporary replacements for CFCs.

The impact on the ozone layer has been encouraging. In September this year, the UN Environment Programme said that the ozone layer over some areas in the northern hemisphere could be completely restored to their pre-1980 levels by as early as the 2030s. The Antarctica ozone hole could be completely healed by the 2060s, it said. Parts of the ozone layer had recovered at the rate of 1 to 3 per cent every ten years since 2000.

What does it mean for climate protection efforts overall?

Because of its success in eliminating ozone depleting substances, the Montreal Protocol is often cited as a model for the problem of climate change. The example, however, is not very suitable. The chemicals that were dealt with by the Montreal Protocol were used in only some specific sectors and their replacements were readily available, even if at a higher cost differential at that time. The economic impact of banning these chemicals, and the disruption it caused, was limited to these sectors. Over the years, these industrial sectors have managed a relatively smooth transition.

Climate change, caused by greenhouse gas emissions, is a much more complex, and all-pervasive, problem. The emission of carbon dioxide happens from the most basic of all activity — production and consumption of energy. All other activities require energy to drive them, and therefore there is no escaping carbon dioxide emissions. Even the so called renewable energies have a carbon footprint. Reduction in carbon dioxide emissions affects economic activity and, in turn, the living standards of people. That is why climate change agreements like the Kyoto Protocol could achieve very little till now, while Paris Agreement faces an uphill task.

Average area of ozone hole, in million sq km, for the period between September 7 and October 13. No data for the 1995 season. (Source: NASA)

Source: The Indian Express

Relevant for GS Prelims and Mains Paper III; Environment