The discovery of the Antarctic ozone hole

Kerri Smith

This is the Nature PastCast, each month raiding Nature’s archive and looking at key moments in science. In this show, we’re exploring a paper published in the 1980s.

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News report

And now, ozone in the news. Recently, scientists discovered a weak spot in the ozone layer over Antarctica. Satellite observations have confirmed a progressive deterioration in the Earth’s protective ozone layer above Antarctica, according to scientists…

Voice of Nature: John Howe

Nature, international weekly journal of science. 16^th May 1985. Letters to Nature, p207. Large losses of total ozone in Antarctica.

Jonathan Shanklin

The paper really changed the way people look at the environment.

Erik Conway

It provided an image of nearly global environmental damage that people could see.

Richard Stolarski

All of a sudden, you look at it differently – wow, we really can affect the planet as a whole.

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Voice of Nature: John Howe

J. C. Farman, B. G. Gardiner and J. D. Shanklin, British Antarctic Survey, Cambridge, UK.

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Jonathan Shanklin

What we discovered at our Antarctic station was quite curious. It seemed that each Antarctic spring – which for the Antarctic is September, October – ozone levels were dropping. I’m Jonathan Shanklin and I was one of the team of scientists that discovered the Antarctic ozone hole.

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Jonathan Shanklin

Concerns were raised, really, in the 1960s and 70s that substances that we were manufacturing, in particular chlorofluorocarbons – the CFCs – might put chlorine high into the atmosphere where it could then photocatalytically interact with the ozone and destroy ozone.

News report

Ozone is an invisible upper atmospheric gas that protects all forms of life on Earth from most of the Sun’s damaging radiation, radiation that can cause skin cancer, eye damage and suppression of the immune system. The harvesting of fish and plant life are also affected. A vast amount of aquatic life has its beginnings…

Jonathan Shanklin

When we were working up to publishing our paper, concerns had been expressed that these CFCs might destroy the ozone layer, that exhaust gases from Concorde might destroy the ozone layer, and the general thoughts were that any destruction would probably take place at high altitude in the tropics.

Richard Stolarski

My name is Richard Stolarksi, and I’m a research scientist who’s worked on ozone for many years. I’m now at the Johns Hopkins University in Baltimore, Maryland. We were looking for, at most, a few percent change in ozone and we weren’t necessarily looking in Antarctica. What they found in that paper was, during the springtime, a 40% or more decline and that that 40% only ten years earlier was not there, so this happened very rapidly. So, basically, it was more than an order of magnitude greater than we expected.

Erik Conway

My name is Erik Conway. I am the historian at NASA's Jet Propulsion Laboratory in Pasadena, California. So, when the British Antarctic Survey paper is published in 1985, a lot of people are rather shocked because during the early 1980s, they weren’t sure whether there was evidence of depletion and that’s because it’s a difficult question to answer. There is a great deal of variation in the density of stratospheric ozone – it varies by season, it varies by latitude – so there were claims of depletion but they weren’t widely accepted yet.

Richard Stolarski

The fluorocarbon-ozone theory was a theory. It’s just a theory. We can’t see it happening. Boom – look at it. There it is.

Voice of Nature: John Howe

Total ozone has been measured at the British Antarctic Survey stations, Argentine islands and Halley Bay since 1957. Whatever the absolute error of the recent values may be, the annual variation of total ozone at Halley Bay has undergone a dramatic change.

Richard Stolarski

Boom – look at it. There it is.

Jonathan Shanklin

One of the tasks that I had when I first joined the Survey was to process the missing data. We had a period of about ten years where the data hadn’t been reduced and doing it manually was quite time consuming. Computers were just coming in. I was given the task of writing the programmes, supervising the digitisation of the data and processing it. I started at the present and was going to work back, and my colleagues really didn’t believe that this was significant. They thought, well, just because you’ve got it one year, it doesn’t count. So, I eventually worked up all the missing years and was able to show it was systematic and if you’ve got something systematic, there has to be something real going on. I think I was probably the little thing in the background that made the difference and it was really a little voice from me being quite persistent that look, we’ve got to do something about this, that finally sort of drove them to right, well, we better write this up and better go to Nature because I think they had a better grasp of what a fundamental discovery this was than I did.

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Erik Conway

Many scientists told me that, in fact, they trusted the British Antarctic Survey people. In other words, they knew them to be good and rigorous scientists, so the initial questioning of those scientists was, well, how could they get such results because what they had found was ozone concentrations are far lower than anyone had ever seen on Earth.

Richard Stolarski

I was with NASA for 35 years, and I had just come off of a stint as a low-level manager and was just getting back into doing some real science, and we had people who had been taking satellite data of ozone. At the time, the amount of data was so massive it was overwhelming and very difficult to deal with. You had to learn how to find the right 9 track tape in a room full of tapes, and it’s really ironic to look at it today because the satellite was taking about 5 GB of data per year and at that time, when you said that, people were overwhelmingly impressed and now I think a lot of people probably run that through their smartphone every month. But at the time, it was an overwhelming amount of data.

Erik Conway

The Goddard team was scooped and they knew it. They went back to their own data and tried to figure out why this ozone hole wasn’t apparent, and it turned out that it was. Well, the Goddard folks had set quality control software to look at the data automatically as it came back from the satellite and mark as potentially bad data anything that showed levels below a certain amount, and these levels of the prediction of the Antarctic Surveys were below that amount. So, when the Goddard folks mapped all these flags of potentially bad data, they were all over the Antarctic, exactly where the British Antarctic Survey said it should be. So, they ultimately wound up corroborating the British Antarctic Survey’s story and getting a bit of egg on their faces too.

News report

It’s being called an unprecedented display of international cooperation to protect the world’s environment. The Montreal Protocol signed today aims at stopping the deterioration of the ozone layer in the atmosphere – that’s the layer which shields us from damaging ultraviolet radiation from the Sun. But there’s a lot of work ahead before…

Erik Conway

So, after the discovery of the 1985 ozone hole, there was already scheduled a set of negotiations over chlorofluorocarbons to reduce, but not ban, the production of chlorofluorocarbons, and what the discovery of the ozone hole does is demonstrate that there really is a problem and probably helped accelerate the negotiations that were already ongoing. The Montreal Protocol, as it’s initially written, was a 50% reduction in production of chlorofluorocarbons – it was not a ban. The ban actually took a number of more years to negotiate and became possible as more evidence that chlorofluorocarbons were actually responsible for the ozone hole was developed by the scientific research that was going on.

News reports

They have discovered a trend. Each spring, over Antarctica a hole in the ozone develops… Satellites photo show that a hole opens for a few months during Antarctica’s springtime…

Jonathan Shanklin

It was very clear when we first looked at the data that we’ve got an ozone decline and I think that’s probably the term we used – a decline in ozone above the Antarctic – and it wasn’t really until you got the satellite images that you could see oh, there’s a hole there. And yeah, with nice coloured graphics it hits you in the face.

Richard Stolarski

It is not clear to me to this day who coined the term ozone hole and when and where it was done. Some complained we shouldn’t use that term, but once you let that term out of the bag, there was no going back. It became the ozone hole and it seems to me that it certainly made it easier to reach a greater part of the public by having a simple key word that you could describe it by.

Erik Conway

The ozone hole was mentioned in newspapers and on TV quite commonly during the 1980s because the interest of environmental organisations kept it on the public radar, I think. The ozone hole actually still appears every year, and it has completely disappeared from public conversation. We have judged it a solved problem even though scientists don’t actually expect it to go away for another 80-100 years.

Richard Stolarski

I really think that the whole episode of the ozone hole discovery and all the subsequent things that happened, in terms of explaining it, mapping it etc., are a huge success story for the science of understanding the stratosphere. We were able, in a very short time, to put together a lot of pieces and to draw a much clearer picture of how this part of the Earth’s system works and what might affect it and what might not affect it.

Erik Conway

So, the legacy of the ozone hole story was that effective environmental action can be taken at the international level to resolve global environmental problems. A great many people compare the ozone depletion problem and the climate change problem.

Richard Stolarski

You have to remember that the ozone hole story was sort of simple and straightforward, and that CFCs had not been part of our economy for that long and they were not the same as carbon dioxide which is coming from our basic energy generation, so that the regulations that limited the CFCs could be handled by the economy quite easily. So, while there are lessons, I think with carbon dioxide we are dealing with a much more difficult problem that goes way beyond the parameters that were involved in the ozone hole.

Jonathan Shanklin

It’s been quite fascinating going back, particularly along the Antarctic Peninsula, on various trips. When I first went to Rothera, we used to get drinking water in the summer from a melt pool that formed on a patch of ice nearby. The last time I was at Rothera, we couldn’t do that because the ice level had dropped so much that the water just spilled out into the sea and I’ve seen the glaciers retreating, slowly, admittedly, but I can see that they’re going back and yes, change is very obvious along the Antarctic Peninsula. The ozone hole story clearly shows that if we have the will to do things, we can succeed. Climate change – the will isn’t there yet, and I fear it will take a disaster or two before that will appears. But once it does, we have the knowledge and the technology to do something about it.

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Voice of Nature: John Howe

Nature. Published by Macmillan Journals Limited, 4 Little Essex Street, London, WC2R 3LF. 16^th May 1985.

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Kerri Smith

You’ve been listening to the Nature PastCast, produced by Charlotte Stoddart and with contributions from Jonathan Shanklin, Richard Stolarski and historian Erik Conway. Next month, it’s back to the 1870s and the starring role of the gorilla in the quest to understand man’s place in nature.