ELI5: Holes in the Ozone Layer?

Have you ever heard someone spray some hairspray and then joke that they just made a new hole in the ozone layer? That joke is pretty bad, partly because it isn’t funny and partly because it’s inaccurate! Let’s find out why in this week’s Explain Like I’m 5: 

What is the ozone layer?

Earth’s atmosphere is made up of layers. The first layer is called the troposphere and it’s the one closest to the earth's surface. This is where weather occurs. All storms, hurricane winds, and fluffy clouds happen in the troposphere. The next layer up is the ozone layer. This layer is relatively thin and takes up the space about 9-18 miles above earth’s surface. The ozone layer is made up of ozone gas, or O3. Ozone is important because it acts like sunscreen for the planet and absorbs roughly 98% of harmful UV-B radiation from the sun. UV-B causes skin cancer, and also degrades ocean ecosystems and harms plants. In fact, there would be millions more cases of skin cancer in the US if the ozone layer didn’t protect us. 

There are holes in the ozone layer, right?

Not quite. The ozone layer is thin to begin with - as in, not very dense.  There are about 10,000,000 molecules of “air” in the troposphere for every 3 molecules of ozone in the ozone layer. When people talk about the hole in the ozone layer, they’re really talking about patches of the layer that are even thinner than usual. When the ozone layer gets too thin, more UV-B radiation gets down to earth’s surface, and that’s bad for everyone. 

So what causes the ozone layer to get too thin?

Scientists started noticing that the ozone layer was getting some alarmingly thin patches in the 1980s and connected the problem to CFCs, or chlorofluorocarbons. CFCs could be found mostly in refrigerants, but also in aerosols like hairspray, insecticides, and the type of whipped cream canisters in the photo. The picture for this article really should be an old refrigerator, but that’s not as cute as those whipped creams. When CFCs work their way up past the troposphere like a Trojan horse, the UV-B rays start to break them down into smaller molecules, including chlorine atoms, that can do a lot of damage. Chlorine gas is very unstable and HATES to be alone. So instead of staying alone, it breaks apart the ozone molecules and steals one of the oxygen atoms. The two leftover oxygen atoms are now just oxygen gas and don’t protect us from harmful UV-B rays. That’s bad enough, but it turns out that chlorine atoms are really fickle. Instead of just sticking with the one oxygen atom they already stole, they dump it and break up another ozone molecule looking for fresh meat. One atom of chlorine can destroy more than 100,000 molecules of ozone just by doing this over and over again. The main “hole” in the ozone layer occurs every spring over the South Pole (August - October). Springtime sun shines directly onto the South Pole and all that extra UV-B from the sun quickly degrades CFCs and the whole process ramps up.

What should we be doing to stop the ozone layer from thinning?

The good news is that we already have a great handle on this problem! In 1989, The Montreal Protocol called for countries to ban the production of ozone-harming substances like CFCs. All 197 member countries of the UN signed the agreement and the ozone layer has been recovering since. The fact that UN countries no longer make products with CFCs means that the old hairspray joke is even worse than it was to start with. According to National Geographic, the world would be at least 25% hotter now if the Montreal Protocol didn’t exist. Frankly, I find this to be an unbelievable claim and am taking it with a grain of salt until I can find the research behind that figure. Some developing countries still use CFCs in refrigerants, but the ozone layer is projected to have healed itself within the next 50 years. Now most countries use a new substance, hydrochlorofluorocarbons or HCFCs. These are much less damaging to the ozone layer, but they are a powerful greenhouse gas. Granted, HCFCs are a very small slice of the greenhouse gas pie, but we should still try to move away from them. In fact, an addendum to the Montreal Protocol in 2016 said that countries needed to reduce their use of HCFCs by 80% in the next 30 years. Scientists are already at work creating a newer generation of refrigerants that will be even better.

So there you have it! Not the biggest problem that we’re facing right now, but still a good one to be educated about. Have any questions? Feel free to drop them in the comments or start a discussion in the Troop 7B facebook group!