Earth’s protective ozone layer on track to heal within 50 years

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The Earth’s protective ozone layer is healing at a rate that climatologists believe will see the stratospheric hole over Antarctica fully closed in the next five decades – but challenges remain.

According to a United Nations report presented at the American Meteorological Society convention in Denver on Monday, the latest scientific assessment of the status of the ozone layer suggests that recovery is making steady progress.

This comes more than 35 years after the landmark Montreal Protocol, signed in 1987, when every nation in the world agreed to stop producing ozone-depleting substances that attack the layer of gas in the Earth’s stratosphere that shields the planet from radiation linked to skin cancer, cataracts and crop damage.

Progress is slow, however. According to Paul Newman, co-chair of the scientific assessment panel, “in the upper stratosphere and in the ozone hole we see things getting better”. 

The global average amount of ozone 30 kilometres above the planet won’t be back to pre-1980 levels until about 2040, and it won’t be back to normal over the Arctic until 2045.

Meanwhile, in Antarctica – where the ozone layer is so thin there’s a giant gaping hole – the levels won’t be fully fixed until 2066.

This file image released on 1 December 2009, shows a combination of two images released by the Nasa Earth Observatory showing the size and shape of the ozone hole in 1979 and in 2009. © AFP – NASA EARTH OBSERVATORY – HANDOUT

Testament to success of Montreal Protocol 

World Meteorological Organization Secretary-General Professor Petteri Taalas said in a statement: “Ozone action sets a precedent for climate action. Our success in phasing out ozone-eating chemicals shows us what can and must be done – as a matter of urgency – to transition away from fossil fuels, reduce greenhouse gases and so limit temperature increase.”

Signs of healing were reported four years ago but were slight; the latest report indicates the rate of recovery has solidified.

Report co-ordinator Newman, who is chief Earth scientist at NASA’s Goddard Space Flight Center, revealed that chlorine levels are down 11.5 percent since they peaked in 1993, and bromine – which is destructive to ozone, but less prevalent in the air – dropped 14.5 percent since its 1999 peak.

A brief history of the ozone emergency

1975–84: Ozone hole discovered above Antarctica

  • Scientific research reveals drop in the ozone layer in the stratosphere above the Halley Bay scientific base in the Antarctic.
  • US chemists Mario Molina and Sherwood Rowland credited with linking chlorofluorocarbons (CFCs) – used in refrigeration, hairspray and other aerosols – to the destruction of the ozone layer.
  • The two researchers win the 1995 Nobel chemistry prize for their research.

1985: First ozone treaty 

  • 28 countries sign up to the Vienna Convention for the Protection of the Ozone Layer – the first international treaty on the issue – which commits members to monitoring ozone depletion and its effects on human health and the environment.
  • The USA – which banned the use of CFCs in aerosols in 1978 – ratifies the convention in 1986.

1987: Montreal protocol

  • The Vienna Accord paves the way for the landmark Montreal Protocol which sets targets for ending the production and consumption of ozone-depleting substances.
  • Initially signed by 24 countries and European Economic Community, it is eventially ratified by all UN members – making it one of the most successful environmental treaties ever.

1989: Ozone crater over the Arctic 

  • In early 1989, a thinned area is also detected in the ozone layer over the Arctic.
  • By 1990, the Montreal Protocol is strengthened to end production of CFCs in industrialised countries by the end of 2000.

1995: HCFC ban

  • By 1995, the European Union has totally banned CFCs and begins eliminating replacement gases called HCFCs (hydrochlorofluorocarbons, used in refrigeration and air-conditioning) which both deplete the ozone and are powerful greenhouse gases.
  • That December, industrialised countries agree to ban HCFCs by 2020.

2006: Record hole

  • The biggest ever hole seen in the ozone layer over the Antarctic is recorded in late September 2006.
  • In September 2007, an accord is reached in Montreal to advance by 10 years to 2030 the elimination of HCFCs in developing countries.

2016: Gap closing

  • US and UK researchers write in Science Magazine that the hole over the Antarctic is shrinking. They expect it to completely heal by 2050.

2023: Full recovery within four decades

  • On January 9, 2023 the UN announces that the ozone layer is on track to fully recover within four decades.
  • But it warns controversial geoengineering schemes to blunt global warming could reverse that progress.

Scientists and environmental advocates across the world have long hailed the Montreal Protocol, which banned CFC chemicals often used in refrigerants and aerosols, as one of the biggest ecological victories for humanity.

That bromine and chlorine levels “stopped growing and are coming down is a real testament to the effectiveness of the Montreal Protocol”, Newman added.

From the 1950s to the 1980s, people could buy aerosol cans full of CFCs that eat away at the ozone.

Decades later, not only are the substances banned but they are no longer in people’s homes or cars, having been replaced by cleaner substances.

The United Nations believes that global action reparing the ozone layer saves about 2 million people from skin cancer every year.

Beware ‘planet-cooling technology’

However, the report also warned that efforts to artificially cool the planet by putting aerosols into the atmosphere to reflect the sunlight would thin the ozone layer by as much as 20 percent in Antarctica.

With carbon emissions continuing to rise and time running out to avoid some of the worst impacts, controversial geoengineering schemes are moving to the centre of climate change policy debates. 

These include proposals to blunt global warming by depositing sulphur particles into the upper atmosphere. 

Scientists have cautioned this could sharply reverse the recovery of the ozone layer.  

So-called stratospheric aerosol injection (SAI) is increasingly seen as a potential stop-gap measure for capping temperatures long enough to tackle the problem at the source. 

Natural events have demonstrated that it works – such as the 1991 eruption of Mount Pinatubo in the Philippines, which spewed millions of tonnes of dust and debris into the atmosphere and lowered global temperatures for about a year.

Injecting 8 to 16 million tonnes of sulphur dioxide into the stratosphere each year – roughly equivalent to Pinatubo’s output – would cool Earth’s temperature by about 1°Celsius.

However, there is a trade-off: the ozone layer would be reduced to its 1990 levels – only a third of what it was before the impact of human activity – and the planet would see the continued depletion of ozone, while managing solar radiation would remain a serious problem.

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