Nature

Ozone layer recovery: Jury is still out, but verdict likely soon

Recent studies show that new dreams driven by short-time achievements make us forget the real objective and purpose of long-term missions. The global environmental accord called The Montreal Protocol on Substances that Deplete the Ozone Layer is a case in point. Its key objective is to protect the stratospheric ozone layer that shields life on the Earth. Has that mission been achieved?

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The ozone layer is a protective screen about 8-50 kms from Earth’s surface. It filters out high-energy, destructive UV-rays from the Sun. After more than a decade of scientific postulations, vigorous studies and observations it was revealed that the ozone shield has been threatened by man-made chemicals, mainly chlorofluorocarbons (CFCs) and their emissions into the atmosphere.

Depletion of the ozone layer was considered a catastrophic risk to the life on the Earth.

In 1987, world leaders, after protracted negotiations under the UNEP, agreed that the way to protect the life-saving ozone layer was to phase-out production and consumption of CFCs, and nearly 100 other man-made ozone-depleting chemicals that travel up into the stratosphere. The Montreal Protocol was thus born and since then, has become a universally ratified treaty. All the member-states of UN are Parties to the Protocol.

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The Protocol will celebrate its 30th Anniversary later this year in Montreal. Indeed, there are reasons to be upbeat. Ninety-eight per cent of the production of ozone-depleting chemicals has been shut down. Former UN Secretary General Kofi Annan said in 2000 that the Montreal Protocol was “perhaps the single-most successful international agreement so far”. More recently in 2017, UN Secretary-General António Guterres, called it as ‘milestone for all people and our planet’

The numbers are astounding and overwhelming. Without the Protocol, we could have got sunburnt in five minutes. There would have been an additional 280 million cases of skin cancer, 1.5 million skin cancer deaths and 45 million cataracts in the US alone, according to the Environment Protection Agency.

If the impact due to loss of food production due to UV rays penetrating through the ozone layer and the weakening of human immune system is considered, one can say that Earth has avoided the possibility of a sixth extinction.

Last year, there were global headlines when all countries unanimously agreed to amend the Protocol to include the “phase-down” of hydrofluorocarbons (HFCs). That was an unprecedented decision because HFCs do not only deplete the ozone Layer — albeit in a much weaker way than CFCs — they have a dangerously high global warming potential.

Interestingly, they are also part of the six Green House Gases (GHGs) packaged in the Paris Climate Agreement that aims to control their emissions. The countries, in other words, decided to help the Paris Climate Agreement by using another international treaty — the Montreal Protocol. Many called it “surrogate mothering” by the countries.

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The reasons for this extraordinary “inter-treaty” intersect was that HFCs were mainly introduced to replace CFCs under the Montreal Protocol. In a way, the countries wanted to correct the inadvertent error they had committed by introducing HFCs. They rightly thought that all the successful armoury in the form of institutional and financing resources were accessible. Hence dreaming of conquering HFCs — albeit a new territory — was logical.

So, has the ozone layer being saved and is it on recovery mode?

One of the key factors to assess the success in its recovery is to measure the depth and extent of annual appearance of the “Ozone Hole” over Antarctica. Every spring (August to October), when the sun rays break out over the frozen continent, the chemical species riding on the tiny ice particles in the Antarctic vortex start destroying the ozone layer. This annual “dance festival” tells us the extent of the ozone hole’s recovery.

Flying over the lower end of the polar vortex recently in a DC-8 NASA aircraft loaded with 23 instruments, Paul A. Newman, the Agency’s Chief Scientist, measured the chemical radicals in the vertical column of atmosphere.

Newman said the NASA mission recorded that the 2017 ozone hole was unusually small and weak in depth. However, he was quick to add that “this weaker ozone hole is a result of year-to-year variability of the meteorology and it is still not known if it is an evidence of recovery because the meteorological variability masks the long-term projected trend”.

Variability is evidently having a last laugh.

In 2000, the hole had a record size. In 2002, it was half the size. In 2006, it was almost another record size. In 2012, it was second smallest. In 2016 it was again worse than average.

As per the latest 2014 UNEP-World Meteorological Organisation’s Scientific Assessment Panel report, the measured tropospheric concentrations of ozone depleting substances continue to decrease.

Susan Solomon, pioneer atmospheric scientist and Professor at MIT, stated in 2016 that we had succeeded in creating a situation for ozone layer recovery. The expected recovery is projected by the Science Assessment Panel by middle of this century.

I asked Dr Newman: “Tell me doctor, is the ozone layer finally recovering?”.

Quick came his response from the southern tip of Chile: “Ozone-depleting substances in the troposphere are decreasing. Chlorine and Bromine species in stratosphere are decreasing. On recovery of the Ozone Layer? Jury is still out, but we’re all pretty sure that they’ll soon render a verdict!”

(Rajendra Shende is Chairman, TERRE Policy Centre, IIT alumnus and former Director, UNEP. Views expressed are personal. He can be contacted at [email protected])

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