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The stratosphere -

High above the Earth’s surface, between six and 30 miles (9.6 to 48.2 km) above to be exact, lies a layer of the atmosphere known as the stratosphere.

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The ozone layer -

The stratosphere is home to much of the Earth’s ozone, a colorless or pale blue gas that plays an important role in making our planet habitable.

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Natural SPF -

The ozone layer acts as a protective shield against the Sun’s ultraviolet rays; without it, there would be no life on Earth at all.

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Panic! -

There was unsurprisingly great alarm in the 1980s when the British Antarctic Survey published research that confirmed there was a hole in the ozone layer.

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CFCs -

The Survey suggested a link between damage to the Earth’s ozone layer and the use of chlorofluorocarbons (CFC), which are found in aerosols and cooling devices.

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Earlier discovery -

In fact, scientists Mario Molina (pictured) and F. Sherry Rowland had already suggested in 1974 that CFCs could destroy the ozone layer. Unfortunately, their work was rejected.

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CFCs everywhere -

The use of CFCs in products ranging from refrigerators to industrial cleaning agents proliferated, and by the mid-1980s the situation was perilous.

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Action -

Thankfully, at that point governments rallied and took unprecedented steps to repair the hole in the stratosphere that acts as the Earth’s natural SPF.

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The status quo -

It is for that reason that we stopped hearing so much about the hole in the ozone layer and the potentially devastating effects it could have.

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Relief -

According to Laura Revell, an associate professor at the University of Canterbury, New Zealand, “It’s not the same cause for alarm that it once was.”

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The Montreal Protocol -

In 1987, a global agreement called the Montreal Protocol was adopted, with the aim of protecting the ozone layer. The plan was to phase out the substances that deplete it.

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Very effective -

The Montreal Protocol was remarkably effective: by 2009 some 98% of the chemicals that countries had agreed to phase out were gone.

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Why it worked -

The success of the Montreal Protocol may be put down to the fact that it recognized “common but differentiated responsibilities” for developed and developing countries.

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Why it worked -

Phasing-out schedules were staggered, and there was a fund established to provide financial and technical aid to those countries who needed it to become compliant.

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CFC replacements -

Inevitably, other substances were introduced to replace CFCs, and unfortunately some of these turned out to be bad for the climate, too. In turn, the treaty also restricted these.

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Universally ratified -

The Montreal Protocol was signed by every country in the world, making it the only treaty ever to be universally ratified. It is a great example of international environmental cooperation.

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Skin cancer prevention -

There are some models that suggest the treaty and its amendments have helped prevent up to two million cases of skin cancer every year.

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Widely acknowledged -

It is now widely accepted among scientists that if the world had not banned CFCs, we would currently be in a dangerous situation.

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Verbatim -

According to US government researcher Susan Solomon, "By 2050, it's pretty well-established we would have had ozone hole-like conditions over the whole planet, and the planet would have become uninhabitable.”

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Going forward -

The success of the Montreal Protocol is widely recognized, but scientists have also called out the importance of regularly monitoring environmental variables.

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Volcanoes -

Indeed, there are certain risks in the stratosphere’s future. Major volcanic eruptions, for example, can cause ozone depletion.

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Nitrous oxide -

Nitrous oxide, too, can be damaging to the ozone layer. The greenhouse gas is not controlled by the Montreal Protocol, and emissions are on the up.

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Learnings -

According to Revell, "It's really important we do keep in mind the lessons learned from the ozone hole story and make sure we're constantly aware of what's going on in the stratosphere.”

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Parallels -

It is tempting, too, to draw comparisons between the disappearing ozone and the climate change crisis we face in 2023.

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The obvious comparison -

We might question why international governments have not yet found a solution to climate change, given that the Montreal Protocol demonstrates their ability to solve such complex issues.

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Key difference - It is worth remembering, however, that the main culprit in climate change is fossil fuels and these are much more pervasive and therefore difficult to replace than CFCs.

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Food for thought -

The success of the Montreal Protocol is a great testament to international environmental cooperation, but can its lessons be used to tackle the current problem?

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Good news in 2023 -

A 2023 UN report says human action to save the ozone layer has actually worked, and Earth's protective layer is on track to recover within just decades, as per BBC. The report, co-produced by UN, US, and EU agencies, says that if current policies are maintained, the ozone will be restored, though at different points around the world. Over the Antarctic, where the depletion was the worst, the ozone is expected to recover by 2066; over the Arctic it is projected to heal by 2045; and everywhere else it should take around two decades. We have the Montreal Protocol to thank for coming so far, but the continued progress still depends on our continued efforts. 

Sources: (BBC) (UN Environment Programme)

See also: How whales help to combat climate change

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