����ý

This article was last updated in September 2019

We’re quite lucky that we live on Earth.

We’re in what’s known as the Goldilocks Zone, the habitable part of the Solar System that has just the right conditions for water to form, and for life to flourish. This zone really narrow, so it’s a stroke of luck that our planet falls in it. However, it’s not the only factor playing a part in sustaining on our planet.

One of those is the ozone layer. It’s basically the Earth’s sun cream - it protects the planet from harmful ultraviolet (UV) radiation, the kind that causes our skin to burn.

Once upon a time, the ozone layer was a hot topic in the news - everyone was told to chuck out their hairsprays for fear of damaging the planet.

But it’s not spoken about quite so much anymore, and there’s a good reason for that - it’s something of a success story.

But how does the ozone layer work?

The Earth’s atmosphere has six layers. In the second layer, the stratosphere, you can find the ozone layer, which is made up of a gas called (wait for it) ozone.

Ozone molecules are formed of three oxygen atoms, and is what’s known as a trace gas. This means that there’s not a lot of it in our air, however the amount there is essential.

Essentially the ozone layer absorbs the Sun’s most harmful UV rays - 98% of them in fact. This is why it’s so crucial that damage to it is limited, otherwise problems such as skin cancer could be much more likely. In fact, if there was no ozone layer at all, we wouldn’t be able to live on Earth.

What would happen without it?

To answer that, we only have to look at one of our closest neighbours, Mars. As far as we’re aware, life doesn’t exist on Mars, but the red planet also exists in the Goldilocks Zone, so by all accounts it should be habitable.

A large part of the reason why it’s not is due to the ozone layer, or lack of one. Without that barrier, UV rays fry pretty much every useful organic material and plant. That mean it’s hard for flora and fauna to sustain itself, and crucially no way to carry out photosynthesis which provides oxygen.

What damages the ozone layer then?

Chemicals called chlorofluorocarbons, which are made up of chlorine, fluorine and carbon atoms, are the biggest culprit in ozone depletion. More commonly known as CFCs, they can be found in fridges, aerosols and plastics.

When they’re released into the atmosphere and exposed to sunlight, the UV radiation causes the molecule to break down into their individual atoms. When chlorine is separated from the CFCs and reacts with ozone, it rips apart the ozone molecule, leaving the layer thinner than before.

How damaged is the ozone layer?

In 1974, two scientists from the University of California called Mario Molina and Sherwood Rowland discovered the threat CFCs posed to our ozone layer. In a nutshell, they discovered that there was a limit to how much chlorine the ozone layer could absorb, and once that limit was reached, we would no longer have one.

At the time, CFCs were used in lots of things. One of the biggest offenders were the fridges in our kitchens. CFCs were used as a refrigerant as they could absorb heat from around them, keeping your food cold.

The danger of CFCs was reiterated in 1985 by a group of Cambridge scientists. They found what was often called a ‘hole’ in the layer over Antarctica, and that it had been caused by the chemicals. In fact the hole was more like a very thin patch, and more were found across the globe in yearsto come.

This was extremely worrying. One atom of chlorine could destroy more than 100,000 ozone molecules, which meant that it was disappearing faster than it could replace itself, and scientists predicted that by 2050, it would be completely gone.

What was done about it, and did it work?

Luckily the world took notice, and something called the Montreal Protocol on Substances that Deplete the Ozone Layer (catchy) was signed by lots of countries around the world. This is a global agreement that stated all countries must phase out the use of CFCs in manufacturing and elsewhere, with the aim of eventually stopping their production altogether. It was signed in 1987 and came into force in 1989.

The effect it had was astounding. The US Environmental Protection Agency (EPA) estimated that since then the US has avoided:

• 280 million cases of skin cancer
• 1.6 million deaths from skin cancer
• 45 million cases of cataracts

Not only that, but it’s prevented further changes to our climate and weather, too. The chemicals are what are known as ‘super-greenhouse gases’, and if we had carried on releasing them into the atmosphere at the rate we were, one study from Columbia University found that hurricanes and cyclones would have tripled in intensity.

So, is it fixed?

No, but it seems to be getting there. In 2018, NASA found the first direct proof that the ozone layer was recovering. Their research showed that between then and 2005, ozone depletion was reduced by 20%.

If this is kept up, scientific assessments show that the ‘holes’ could be completely repaired by about 2060.

However, some scientists say that this isn't a reason to become less vigilant in our conservation efforts. Dr Jonathan Shanklin, who was one of the first people to discover the ozone layer was thinning, recently told ����ý News that the recovery cannot be taken for granted, and "we cannot be complacent".