Whatever happened to the hole in the ozone layer? - Stephanie Honchell Smith
In the 1980s, the world
faced a huge problem:
there was a rapidly expanding hole
in the ozone layer.
So, what happened?
And is it still there?
Let’s go back to the beginning.
The Sun makes life on Earth possible,
but too much exposure to its UV radiation
damages plant and animal DNA.
Thankfully, about 98% of that radiation
is absorbed by ozone molecules
dispersed in the stratosphere,
which are continuously broken apart
and reformed in this process,
maintaining a delicate equilibrium.
But in the early 1970s, two chemists—
Mario Molina and Sherwood Rowland—
demonstrated that widely used chemicals
called chlorofluorocarbons, or CFCs,
could upset this balance.
CFCs were developed in the 1920s
by three US-based corporations
as coolants for refrigerators.
Unlike existing alternatives—
such as ammonia or methyl chloride—
CFCs were non-flammable and non-toxic—
meaning they wouldn't burst into flames
or cause deadly gas leaks.
They also made great propellants,
foaming agents, and fire-retardants.
CFCs soon found their way into a variety
of everyday items
and became a multi-billion dollar
per year industry.
In the lower atmosphere, CFCs don’t
break down or react with other molecules.
But Molina and Rowland showed
that in the stratosphere,
they're broken apart by UV light,
releasing chlorine atoms.
These then react with ozone,
destroying it faster
than it can be replenished.
A single chlorine atom can destroy
thousands of ozone molecules
before finally reacting with something
else and forming a stable molecule.
Seeing the threat to their bottom line,
CFC producers pushed back
to discredit the scientists,
even accusing them of working for the KGB.
Initial estimates showed
that within 60 years,
CFCs could reduce ozone
concentrations by 7%.
But by 1985, it became clear that ozone
depletion, especially over Antarctica,
was happening much faster.
Here, the extremely cold temperatures
and unique structure of Antarctic clouds
accelerated ozone loss.
Scientists stationed in Antarctica
noticed a massive drop
in overhead ozone occurring every spring.
Satellite data revealed the vast
extent of these losses
and chemical tests confirmed
that the cause was unquestionably CFCs.
NASA soon released visualizations,
which were broadcast around the world
and captured public attention.
If ozone depletion continued,
rates of skin cancer would skyrocket.
Photosynthesis would be impaired,
making plants—
including rice, wheat, and corn—
less productive and more susceptible
to disease.
Global agricultural production
would plummet,
and entire ecosystems would collapse.
But many politicians— weighing immediate
economic concerns over long-term ones—
disagreed about what to do.
The fight to ban CFCs found
two unlikely allies
in US President Ronald Reagan
and UK Prime Minister Margaret Thatcher.
Despite their general opposition
to government regulation,
Reagan, who had undergone treatment
for skin cancer,
and Thatcher,
who was trained as a chemist,
recognized the need for immediate action.
The US and UK, along with Canada, Norway,
Sweden, and Finland,
led calls for an international
ban on CFCs.
In 1987, representatives signed
the Montreal Protocol,
requiring the rapid phasing out of CFCs
and creating a fund to assist
Global South countries
in obtaining affordable,
non-ozone depleting alternatives.
It was later ratified by every country
on Earth—
the only treaty in history
to achieve this.
In 1995, Molina, Rowland,
and their Dutch colleague Paul Crutzen,
were jointly awarded the Nobel Prize
in Chemistry.
As the use of CFCs declined,
the ozone hole began shrinking,
and is predicted to disappear
entirely by 2070.
But we’re not out of the woods yet.
While the ban was a win for the climate,
as CFCs are potent greenhouse gases,
the alternatives that replaced them—
hydrofluorocarbons, or HFCs— are too.
While generally less potent than CFCs,
HFCs still trap more heat
than carbon dioxide
and are contributing to climate change.
To address this, in 2016,
the Kigali Amendment
was added to the Montreal Protocol,
calling for an 85% cut
in global HFCs by 2047.
This alone could avoid up to 0.5°C of
global warming by the end of the century.
Today, as we face the existential threat
of climate change,
the Montreal Protocol serves as a model
for the decisive global cooperation
we need to combat it.
The question is, what will it take
for us to come together again?
