Lessons from the ozone hole

On September 22 (right), the hole in the ozone layer (blue and purple) above Antarctica reached its smallest maximum size in two decades, covering 21.2 million square kilometers. The largest ozone hole on record occurred on September 9, 2000 (left), measuring 29.9 million square kilometers. Credit: GSFC/NASA

On September 22 (right), the hole in the ozone layer (blue and purple) above Antarctica reached its smallest maximum size in two decades, covering 21.2 million square kilometers. The largest ozone hole on record occurred on September 9, 2000 (left), measuring 29.9 million square kilometers. Credit: GSFC/NASA

By Claire

I find that a lot of the time, I am quite negative when it comes to the prospects for future climate change. Most of my posts are quite pessimistic about the chances of reaching a global agreement on limiting carbon emissions in time to make any kind of significant impact on global temperatures. But, honestly, that’s what I believe, and it gets pretty depressing when I start to think about what our future might look like.

BUT… there is hope.

One great success story of the possibilities of global action to stem environmental degradation is that of the ozone hole. 

Now, before I go any further, I feel that I really need to say that the ozone hole is not a product of climate change. I quite often hear people lumping global warming and the hole in the ozone layer into the same sentence. They are two completely different issues – climate change being caused by carbon dioxide, and the ozone hole being caused by CFCs.

So, really simply, CFCs (a.k.a. chlorofluorocarbons) are a man-made chemical, made up of chlorine (Cl), flourine (F) and carbon (C). They were most commonly used in refrigerators and as aerosol propellants. CFCs are relatively unreactive chemicals, which is what made them so popular and widely used. Unfortunately, it was this property that also made them so harmful to ozone.

ozone_depletionWhen CFCs are released from these products, they are able to travel up into the stratosphere, where the ozone layer is situated. Here, the molecule is broken apart by UV light, to produce a free Cl atom:

CFCl3 + electromagnetic radiation → CFCl2 + Cl

This free Cl atom is very reactive, and unfortunately, it is ozone that it reacts with. Ozone is made up of three Oxygen (O) atoms (O3).

Cl + O3 → ClO + O2: The chlorine atom changes an ozone molecule to ordinary oxygen

ClO + O3 → Cl + 2 O2: The ClO from the previous reaction destroys a second ozone molecule and recreates the original chlorine atom, which can repeat the first reaction and continue to destroy ozone.

And so the cycle continues. A single CFC molecule can destroy as many as 100,000 ozone molecules, which has devastating impacts on the ozone layer, creating the hole we currently see over Antarctica.

So that was the problem. Human production and use of CFCs was creating a hole in the ozone layer.

What needed to happen was a reduction and eventual stop in the use of CFCs. And that’s exactly what happened.

Measured and projected CFC abundance in the atmosphere.

Measured and projected CFC abundance in the atmosphere.

Enter the Montreal Protocol. The Montreal Protocol is a global agreement to phase out the use of CFCs in order to limit the destruction of the ozone layer. The Protocol was opened in 1987  and put into force in 1989. CFCs were gradually phased out during the first two stages of the agreement, and were effectively banned in 1996.

The Montreal Protocol is hailed as the most successful international agreement to date.

Observations of the ozone hole taken last year indicate that it was at its smallest maximum extent since 1990. This is largely due to warmer temperatures seen over Antarctica, which help to limit the destructive properties of CFCs. The hole is projected to have completely disappeared by 2050.

So although the outlook for a global agreement on reducing carbon emission doesn’t currently look good, history tells us that the world is able to come together to address large-scale environmental issues, and I for one, am going to use that as a source of hope.

7 responses to “Lessons from the ozone hole

  1. Let’s not forget that an ozone hole formed in the Arctic last year. That may have been the result of extremely cold conditions in the stratosphere, though (that should not be confused with temperatures at the surface).

  2. Hi there! I have found my way to your blog via that of DA Hartley, and would like to introduce you to that of another blogosphere acquaintance of mine in Denver [CO]. He is an atmospheric physicist who is very keen on pointing out to anyone who will listen that the hole in the ozone layer is one of the main reasons why much of Antarctica is not warming as fast as the Arctic. For example: http://weatherdem.wordpress.com/2013/02/12/state-of-polar-sea-ice-february-2013-arctic-below-and-antarctic-above-normal/

    This then, like atmospheric pollution by particulates and aerosols is yet another facet to the problem of anthropogenic climate disruption. The better we get at reducing the cooling effects of some human activities (historic and ongoing), the more we will become aware of the scale of the problem our burning of fossil fuels has caused and is causing.

    I wish you all the best with your research but, sadly, I fear we are now all just shuffling the deckchairs on the Titanic.

    • Thanks for those links Martin. I think that the fact that the ozone hole over Antarctica can account for some of the cooling seen over the region is why people often mix up the ozone hole and climate change as the same issue. As you said, climate change is very complex with all kinds of feedbacks operating in different directions in different regions. It’s quite difficult to effectively communicate this complexity to people who don’t understand how the climate system works. Hopefully blog sites like this one, and the ones you link to help to sort out some of this complexity in peoples’ minds.

      • Hi Claire. The confusion in the minds of many (between CFCs and CO2, Acid Rain and Climate Change, etc) seems totally bizarre to me now but – this is just a variation on the “historians fallacy” – everything seems obvious once it has been explained to you! However, what really struck me from reading Weatherdem’s blog posts about Ozone is that, not only are these disting problems, one is reducing the effect of the other… Your blog looks excellent, so it is going to take me some time to appreciate it fully. Keep up the excellent and varied output.

      • Typo alert – “…not only are these distinct problems…”!

  3. Hi Claire, I work with a large refrigeration company; there have been a number of compromised solutions to finding the right refrigerant for fridges and freezers. CFC was developed because other alternatives were either toxic or flammable, the world then rushed to adopt CFCs also known as Freon without fully understanding its effect on the environment. When the effects were realised HCFCs were developed as a less ozone damaging alternative before later being replaced by HFCs both of which have dramatic effects on climate change in the order of hundreds or thousands times greater than CO2. C02 itself is a good alternative refrigerant to HFC, overcoming the initial technical challenges of higher compression required for it to work effectively. Hydrocarbons although flammable are also another good alternative as they are now able to be used in very small quantities, around an ounce for the average sized freezer, so they pose little risk. As you mentioned the world has come together to tackle damage to the ozone layer but in doing so they initially posed greater risks to climate change, however both issues are now being tackled but there is still a long way to go, particularly in developing countries.

    You can read more about these challenges here: What’s in your fridge?

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