In the late 1980s, there was only one
thing everyone was talking about. It
wasn't Madonna's latest single, leg
warmers, shoulder pads, or even big
hair. It was ozone.
Or more precisely, a vast, hulking great
hole that had opened up in our planet's
life support system, the ozone layer.
>> [music]
>> And the culprit, supervillain gases
known as chlorofluorocarbons,
or CFCs, found in everything from
fridges to deodorants, and they were
destroying the precious ozone in [music]
the stratosphere. By the late '80s, the
hole was reaching sizes of around 22
million square kilometers. By 2040, the
hole would have gone global. By 2050,
the ozone layer could have collapsed
entirely. Harmful UV radiation would
come flooding through, causing huge
increases in skin cancer, cataracts, and
compromised immune systems. Plants and
crops would be failing. The word
"uninhabitable" was being used by
leading [music] scientists.
Before climate change, this was the
greatest environmental apocalypse of our
age. And yet,
we don't seem to talk about it anymore.
Is it because we actually fixed it?
I'm James Shaw, and you're watching
Astro Earth. Join me in this video as we
discover the truth about the hole in the
ozone layer. We'll get to the bottom of
what it is, why it's there, and how
humanity managed to fix it. And I'll
explain why we might not be out of the
woods just yet. For those of you that
might be late to this ozone party, and
even for those of you that aren't, it's
worth going back to the basics to start
things off. What actually is the ozone
layer? Well, Earth's atmosphere is like
a jacket, or several jackets for our
planet. There are five main layers. The
bit we're most familiar with is the
troposphere. This is where we live. The
troposphere starts on Earth's surface
and extends up to around 20 km. Now,
this actually varies depending on where
you're standing. And no, I don't mean
like on a mountain. It's around 18 to 20
km at the equator, but only 6 km at the
poles. The troposphere is a hard-working
layer. It provides the air we breathe,
contains 99% of the atmosphere's water,
and is where you'll find pretty much all
of our weather. As you climb, the air
gets thinner and colder.
Next up is the stratosphere, which
extends from around 6 to 50 km above the
Earth's surface. The only clouds that
usually venture this high are
cumulonimbus thunderclouds, whose tops
just scrape the lowest part of the
stratosphere, which is why they've got
their distinctive anvil-shaped caps.
They're sort of squashed against the
ceiling of the atmospheric boundary.
Commercial passenger jets fly in the
lower stratosphere, trying to stay above
the weather for a smoother ride. In the
troposphere, temperatures fall as you
climb, but in the stratosphere, they
actually increase with altitude. And
there's a reason for this, and it's
actually the reason you're watching this
video. This is where the ozone layer is.
Beyond that is the mesosphere, the
thermosphere, and the exosphere. And
past that, well, that's space. And we've
actually got a whole other channel for
space. So, if that's your thing, why not
check it out after this video?
Anyway, back to ozone. Every layer of
the atmosphere has a specific job to do.
And the ozone layer is possibly the most
important of them all.
But to understand why that is, we need
to understand a bit more about what this
vital layer is actually made of.
We're all familiar with oxygen, O2. It's
what we're all breathing in right now.
Well, ozone is O3. That's three oxygen
atoms combined to form a pale blue gas.
You know that sort of sharp, fresh smell
you often get just after a thunderstorm?
Well, that, that is ozone.
Ozone can be both a hero and a villain,
and whether it's good or bad depends on
where it is.
Bad ozone is tropospheric or ground
level. It's a harmful air pollutant and
often the main ingredient in smog. But
good ozone is stratospheric. It hangs
out around 15 to 35 km above the Earth's
surface and basically acts like a
sunscreen for the planet. This is the
ozone layer we've all heard of and it
blocks an incredible 98% of all harmful
UV radiation. Yeah, 98%. It It works
hard. The vast majority of sunlight is
what's known as visible light, the light
we can see, with wavelengths of 400 to
700 nm. Ultraviolet radiation is
actually only 8% of all light and it's
invisible to the human eye, though some
insects, like bumblebees, can see it.
Visible light consists of different
colors that you can see in a rainbow and
UV is no different. It also has its own
spectrum, UVA, UVB, and UVC. They're
classified by wavelengths, so UVA is the
longest and UVC is the shortest. You may
have even seen UVA and UVB on sunscreen
labels. They're what causes sunburn and
can cause skin cancer.
UVB and UVC are not only incredibly
damaging to us, but they mess with all
sorts of stuff, including photosynthesis
and the productivity in plants and
crops. They damage DNA, suppress immune
systems, and can even reduce survival
rates. In fact, UVC radiation is used to
disinfect hospitals. The reason being is
because it can quite literally kill
nearly everything.
And here's where the ozone layer comes
in because it screens all of the most
harmful UVC radiation and the vast
majority of UVB. [music] Quite simply,
without it, the radiation would
literally sterilize the Earth's surface.
But here's the thing. Ozone is what's
known as a trace gas. That means there's
not a lot of it, basically. In fact,
even in the stratosphere, ozone
concentration is only about 15 parts per
million.
If you took all the ozone in the world
and spread it across the Earth's surface
like a kind of ozoney jam, it would form
a layer only 3 mm thick. That's the same
as two tiny pennies.
And if you did that same thing with the
rest of the atmosphere, that atmosphery
jam would be 8 km high and very sticky.
So, what happens when you discover some
of that precious ozone is missing? This
animation on your screen shows the
actual hole in our ozone layer tracked
over two decades.
The blue and purple mark the area with
the least ozone. Now, technically, this
isn't a hole, I know, in shape. It's a
region of exceptionally depleted ozone.
But, hole was snappier and more
importantly, more concerning to the
general public. Now, in 1979, there was
no significant hole at all. And then it
just grew and grew and grew and grew,
covering not just Antarctica, but
occasionally stretching as far as South
America or even New Zealand. By the year
2000, it measured 28.4 million square
kilometers, almost seven times the size
of the EU or three times the size of the
United States.
Looking back with hindsight, it seems
pretty obvious that this was a
planetary-scale emergency. But, how did
we even realize we had a problem in the
first place?
The answer, as with so many things, is
science.
We first started measuring ozone to try
and understand more about how our
atmosphere worked. By the late 19th and
early 20th centuries, scientists had
already established that stratospheric
ozone acted as a vital shield against
harmful radiation.
In the mid-1920s, Gordon Dobson, a
British scientist, invented a new type
of spectrophotometer,
an instrument that monitors UV levels
from the ground to work out how much
ozone there is in the stratosphere.
More than a century later, and the
Dobson spectrophotometer is still the
foundation of the global network for
monitoring atmospheric ozone even today.
In fact, what are known as Dobson units
are now the gold standard for monitoring
the ozone hole. So, 300 Dobson units is
the ideal amount of ozone. It's what
gives us that metaphorical 3-mm layer I
mentioned before. Less than that, and
you're in trouble.
And we started spotting signs of exactly
that kind of trouble in the 1970s and
the 1980s.
British Antarctic Survey scientists Joe
Farman, Brian Gardiner, and Jon Shanklin
took the world by storm when their
groundbreaking paper, "Large Losses of
Total Ozone in Antarctica", published in
Nature in 1985.
Working through a backlog of data from
the Dobson spectrophotometer
and the Halley base in Antarctica,
Shanklin discovered a systematic and
rapid decline in the amount of
springtime ozone. In 1979, it was
relatively fine, but by 1984,
the stratospheric ozone layer over the
Halley base was only around 2/3 as thick
as in previous decades.
Something was happening to our ozone,
and it was happening fast.
Between 1986 and 1987, the race was on
to find out what exactly was causing the
loss. Scientists from the hunt for
ozone-depleting substances, or ODS, the
BAS team had theorized that possible
chemical causes must be considered, and
they weren't the first.
If you've heard of the ozone hole, then
you already likely know that
chlorofluorocarbons
or CFCs were eventually found out to be
the culprits, but they simply weren't in
the public consciousness back then. They
were an invisible part of our daily
lives using aerosols and fridges, a sort
of killer lying in darkness waiting.
But way back in 1974, scientists Mario
Molina and F. Sherwood Rowland published
a paper theorizing that
chlorofluorocarbons could destroy ozone
in the stratosphere, although their
paper focused on chlorofluoromethanes
only. Now, at the time their theories
were shot down by the industry and they
were denounced as scaremongers. Their
work was literally called pure science
fiction.
As a side note, and I do quite enjoy
this, Molina and Rowland were later
awarded the Nobel Prize in 1995 for
chemistry, so they did win
>> [music]
>> in the end. Anyway, in 1986, Susan
Solomon, a researcher at NOAA, led a
team to McMurdo Base to find out exactly
what was going on. See, Solomon had
theorized that if CFCs were responsible
for ozone depletion, then there would be
high levels of chlorine oxide radicals
in the stratosphere. And guess what?
There were. Molina and Rowland had been
right all along. So yes, there was a
hole, and yes, it was caused by humans.
Shock.
But one question still remained, how
exactly did CFCs do all of this? Before
we get into the chemistry, if like me,
you're quite enjoying a rather more
positive climate news story for once and
you fancy some more like this, well then
I've got more good news. I've been a
keep the good news going a little bit longer and head back to Ozone?
Let's do some chemistry, shall we? So,
ozone is produced when oxygen molecules
absorb UV light from the sun and split
[music] into two single atoms. One then
reacts with an oxygen molecule to become
O3. Now, ozone is pretty unstable. If
you add a bit more sunshine, it can
split back into O2 with one lonely
oxygen atom left sort of spare, allowing
the cycle to begin all over again. It's
like a self-replicating planetary
sunscreen whenever you need [music] it.
Until you throw some chlorofluorocarbons
into the mix. Then things get messy.
CFCs are one of those things us humans
thought we were inventing to make life
better, easier, and cheaper. They first
popped up in the 1890s and came into
widespread use in the 1930s.
Primarily used as coolants in
refrigerators and air conditioners to
replace toxic gases like ammonia and
methyl chloride. They were also pretty
effective in aerosols like deodorant and
hairspray, making perfect propellants in
the pressurized cans. It's important to
remember when we look back at these
things and obviously hindsight's a
beautiful thing that at the time CFCs
were considered perfectly safe. They
were wonder chemicals to some,
non-toxic, non-flammable and stable.
CFCs are halogenoalkanes,
which are molecules consisting of
carbon, fluorine and chlorine atoms. The
carbon-chlorine bond is long and
relatively weak. Now, these molecules
can float up into the stratosphere where
the UV rays from the sun provide enough
energy to break that carbon-chlorine
bond.
Bonds like the one between carbon and
chlorine are called covalent bonds and
they consist of two electrons.
When it breaks, one of those electrons
goes to the carbon and one to the
chlorine, giving them an unpaired
electron each. Species like these are
called free radicals and they are very
reactive.
chlorine radicals collides with an ozone
molecule, it breaks one of its
oxygen-oxygen bonds, creating oxygen and
a chlorine monoxide radical, ClO. This
can react with another ozone molecule,
producing oxygen and another chlorine
radical, which goes on to react with
more and more and more and more. In
fact, just one chlorine radical can
break down more than 100,000 ozone
molecules into oxygen.
Now, given that it's necessary for life
on our planet, you could be forgiven for
thinking that more oxygen would be a
good thing, right? Well, it's good if
you're on Earth's surface and you need
to breathe, but it's not so good in the
stratosphere, where you'd rather have
the ozone keeping those UV rays at bay.
The ozone-munching part of this story is
one most people already know, but what
most people don't realize is that while
chlorine radicals do ultimately destroy
ozone, they don't necessarily do it
immediately.
They require a very special set of
conditions, and this Well, this is where
Antarctica comes in. You may have
noticed that the hole in all of these
satellite images is always mostly over
Antarctica, and there's a very good
reason for that. Antarctica is the
highest, driest, windiest, and coldest
place on Earth. It's a continent with no
countries and no permanent population to
speak of, unless you count the penguins,
which I do.
So, this can't be CFC ground zero. How
many penguins are using fridges and air
conditioners and hairsprays? Well,
here's what's happening. The Earth's
atmosphere is continuously being stirred
by winds. So, ozone-depleting gases
could end up anywhere.
90% of CFCs and halons, their bromine
equivalents, have been released in the
northern hemisphere, Europe, Russia,
Japan, and North America. But, they rise
up to the stratosphere in the tropics,
and they are then blown polewards. And,
as we mentioned, Antarctica is cold,
very cold. In the long months of winter
darkness, a whirlpool of winds called
the polar vortex traps super cold air
over this region, allowing the formation
of polar stratospheric clouds. Now,
these clouds are perfect for CFCs to
start breaking down into those chlorine
radicals.
When the sunlight returns in the
Antarctic spring, that chlorine that's
been building up all winter starts to
kick into gear, shredding through the
ozone at an incredible rate.
The hole just keeps growing bigger and
bigger and bigger until it stabilizes
with the weakening of the polar vortex
as summer arrives. And then, next year,
the cycle begins again.
This is why the hole is seasonal, and
that is why it's nearly always over
Antarctica.
But, just because it's all the way over
there in Antarctica on a largely
uninhabited continent doesn't make the
ozone hole any less dangerous. It just
means it's further away.
Plus, what are called finger extensions
can shift and expand the hole over
cities in New Zealand and South America.
I mean, back in 2000, residents of Punta
Arenas in Chile were warned to stay at
home during one of the largest seasonal
ozone holes on record. UV levels had
skyrocketed into the danger zone.
Quite simply, without action, this hole
would have kept growing, not just over
Antarctica, but everywhere. The warnings
were stark. By 2040, the hole would have
gone global. By 2065, the UV index in
the US would be 30. Usually, it's just
nine. Strong enough to cause sunburn in
cities like Washington, D.C. in just
five minutes. DNA-mutating UV radiation
would be up 500%.
There would be more cancers, more
cataracts, more compromised immune
systems. Plants, animals, and crops
would struggle. Entire ecosystems would
collapse.
And it wasn't just harmful UV radiation
that was the problem. By the late 1980s,
scientists were already seeing
wide-ranging climate impacts.
Jet streams were changing. Australia got
drier, while parts of Uruguay, Brazil,
Paraguay, and Argentina got more rain.
The nature of the chain reactions meant
that our atmosphere was already loaded
with decades of CFCs yet to even make
their impact. CFCs have a long
atmospheric lifespan. They can hang
around in the stratosphere causing
trouble way after they were used down on
the surface. CFC-11s can last 55 years,
and CFC-12s,
140 years.
Something needed to be done, and
quickly. And surprisingly, well, it was.
For once, the entire world quite
literally came together to act.
And it worked.
In 1987, 197 UN member states adopted
the Montreal Protocol, or to give it its
full title, the Montreal Protocol on
Substances that Deplete the Ozone Layer.
How grand. It was the only UN treaty
ever to be ratified by every single
country on the planet.
This landmark global agreement
introduced a plan for phasing out and
eventually banning CFCs, with other
ozone-depleting substances like HFCs or
hydrofluorocarbons
being added as they were discovered.
Montreal was a real turning point, a
plan to save the ozone layer.
And guess what? All these decades later,
it's still working. CFC emissions have
fallen by an incredible 99%
since the Montreal Protocol was
implemented, and ozone-depleting
substances in the stratosphere, well,
they're falling too. Since peaking
around the year 2000, levels have
declined by about a third relative to
pre-ozone hole levels.
Yeah, as you probably already guessed by
now, things had to get worse before they
got better. All of those chemical
reactions were baked into the system,
but it could have been a whole lot
worse. And this is where it becomes a
proper good news story, because the
ozone layer hasn't just stopped growing,
it's actually started healing.
The Antarctic ozone hole has been slowly
improving in area and depth, if you
remember those Dobson units, since the
turn of the millennium. Now, full
recovery is still decades away, but it's
tantalizingly within reach. It's
predicted we'll see a return to 1980
values by 2040 for the global average.
That stretches to 2045 for the Arctic
and 2066
in the Antarctic, because, yeah, those
polar stratospheric clouds, well, they
really make a difference.
A recent MIT-led study published in the
journal Nature added the cherry on top
of the cake. Ozone layer recovery has
been observed in the past, but this,
well, this is the first study to confirm
healing as a direct result of global
actions rather than natural influences
like weather.
The team borrowed what are known as
fingerprinting techniques from climate
science, matching the specific pattern
of ozone changes across different months
and altitudes against what models
predict. It helped researchers confirm
and quantify the role of us fridge
buying hairspray using pesky humans.
Basically, we broke it
and then we fixed it. And this is all
obviously great news, but what's more is
fixing the hole in the ozone layer is
even helping us with things like climate
change.
Another study published in Nature found
that if CFCs hadn't been banned in the
1980s, they could have raised average
global temperatures by another 2.5° C,
which if you've seen this channel, you
know we really can't be doing.
We can't get complacent though. In 2025,
the ozone hole was only the fifth
smallest since 1992
and it was still on average 18.71
million square kilometers. That's still
twice the size of the contiguous United
States. In a cruel twist of irony,
climate change isn't helping.
Temperature, weather, shifts in the
polar vortex, they can all cause ozone
depletion. Extreme wildfires can be
doubly devastating, producing
pyrocumulonimbus clouds funneling a
cocktail of chemical components into the
upper atmosphere.
Those compounds contain, yep, you've
guessed it, chlorine, which reacts with
the ozone to break it down again.
It's also hard to account for rogue
actors who might be ignoring the ban by
still using CFCs illegally. In 2017, a
crack squad of scientists at Bristol
University noticed rising emissions of
CFC-11, banned since 2010, and turned
detective to trace it back to China. The
factories were eventually shut down and
the emissions did drop, not just in
China, but globally. Someone else had
been breaking the rules, but exactly who
still remains a mystery.
It's tricky because we all still want to
have fridges and aerosols and foam
insulation, but they all need some sort
of chemical cocktail to make them work.
Replacements for CFCs can have their own
consequences. For a while,
hydrochlorofluorocarbons,
or HCFCs, looked like they might do the
trick, but they were also found to
destroy ozone, so they too had to be
phased out. Then HFCs came along, but
they were a potent greenhouse gas, so
they're out, too. Hydrofluoroolefins,
aka HFOs, were mooted as an alternative,
but they have another side effect in the
formation of a forever chemical,
trifluoroacetic
acid. You might have heard of it as
PFAS, a poly- or perfluorinated
substance that will never, ever, ever
break down, and is ringing alarm bells
all around the world for human and
environmental health, and quite rightly
so.
Now, looming over all of this is the
meteoric rise of nitrous oxide, commonly
known as laughing gas, but predominantly
used in agriculture. In the last four
decades, human-caused nitrous oxide
emissions have soared by 40%.
It's now the most significant ODS, or
ozone-depleting substance, that we have,
and it's not covered by the Montreal
Protocol. In fact, the Montreal
Assessment Panel says it's a serious
threat for stratospheric ozone.
Good, another one.
But this alphabet soup of chemicals
isn't the only potential ozone killer
out there. To paraphrase Sir Isaac
Newton, what goes up must come down. In
1985, the year the ozone hole was
actually discovered, there were around
120 successful rocket launches, that's
satellites, payloads, and a record nine
space shuttle missions. It was a busy
old year for space. Now, in 2025, an
incredible 4,510
objects were also launched into space,
overtaking the previous record in 2023
of 2,903.
There's currently around 15,000
satellites orbiting the Earth with
another 50,000
set to join them by 2030.
And once they're finished studying the
planet or guiding your car GPS system,
often satellites are allowed to fall
into the atmosphere, and that's a
problem.
See, what happens when they do that is
they burn up on reentry, and as they do,
they release teeny tiny particles of
aluminum dioxide. And yep, you guessed
it, what does aluminum dioxide do?
Depletes the ozone layer.
The problem is that the new generation
of satellites are extremely short-lived,
maybe 5 years. So, dozens of satellites
could be hurtling back to Earth quite
literally every day, each one
potentially destroying the ozone layer
we've worked so hard to rebuild back up
again.
For now though, the ozone layer is still
healing, and I think we have to take
that as a win, while making sure that
these new threats don't undo all of that
hard work. The truth is life is
complicated, and us humans like to
complicate it even further. The bottom
line is that when you mess with nature,
you're always going to pay the price.
But, on the whole, as climate change
burns all around us, I'd like to think
the healing of the ozone hole is still
basically a good news story, and
sometimes we just need a bit of good
news, especially in climate science.
So, yes, we fixed the hole in the ozone.
That's why we don't really hear about it
anymore, but that doesn't mean we should
just forget about it.
This cautionary tale is a reminder that
each one of our actions has an impact. I
mean, who'd have thought a deodorant
used in Detroit could end up destroying
a vital part of Earth's life support
system over Antarctica.
We could have ignored the warnings, but
we didn't. Collective action on a global
scale turned the ozone hole into an
environmental success story rather than
a planetary emergency.
This to me is unequivocal proof that
science plus public awareness plus
crucially political action can equal
results. The only sobering thought is it
happened once and it doesn't feel like
it's going to happen again. If this same
situation was happening now in 2026,
would we all rally together in the same
way?
I'm not convinced. The success of the
ozone hole shows what humanity is
capable of doing when we all come
together for one unified cause. My worry
is that we don't do that enough. Let me
know what you think in the comments
about this ozone situation and whether
this is the only time that you can think
of as well that humanity's come together
for a wider, greater climate good cuz
I struggle to think of too many
examples. Thanks for watching and we'll
see you in the next one.
you want to do something right now to
help the planet, please do get involved.