Over a century of Antarctic observations have exposed the devastating effects our actions can have on the planet. Environmental disasters that can be directly attributed to human behaviour have widespread or long-lasting consequences and are rarely reversible. Science has uncovered a number of these, forcing governments to impose restrictions on businesses and encouraging us to change the way we live in the process. One stands out for its global impact, creating a worldwide consensus and pioneering environmental policy. The discovery of the ozone hole.
The year was 1985 and the world needed to act fast. Demonstrating the power of swift acting policy, a complete worldwide ban of the manufacture of chloroflurocarbons (CFCs) was implemented just five years later. The action is working – observations 30 years on predict that the hole will return to the same level as in the 70s by 2080.
CFCs were developed in the 1930s as a harmless alternative to the ammonia and sulphur dioxides used at the time in refrigerants and were employed extensively in coolants and spray-propellants. Initially advertised as safe and non toxic, one of the compound’s chemicals, chlorine, quickly built up in the ozone layer atmosphere where it is not naturally present. The quantity of chlorine in the ozone layer cannot be attributed to any natural sources.
Vital to all life on our planet, the ozone layer is located 12-19 miles above Earth and absorbs 97-99% of ultraviolet (UV) radiation from our Sun. UV rays have been directly linked to skin cancer in humans and genetic damage in other organisms. CFCs are broken down in the presence of UV radiation at ozone layer altitudes and chlorine is released as a free radical. One chlorine radical can break down some 100,000 ozone molecules in its 20-100 year stay in the atmosphere. A major loss of UV absorbers.
Over the Antarctic this depletion is severe enough to create a hole. The extreme cold of the polar regions aggravates the reaction resulting in ozone declines of up to 70%. In 1985 a group of British Antarctic Survey (BAS) scientists published the seminal paper in Nature describing this hole. The Montreal Protocol banning CFCs was drawn up just five years later.
Professor John Shanklin was one of the BAS team who penned this first paper. I contacted him from London whilst he was on board the RRS Ernest Shackleton en route to the Halley Research Station in the Antarctic.
NASA, NOAA data show significant antarctic ozone hole remains
This is your 19th trip to the Antarctic, are you working on the same projects each time you return? How have the bases changed since your first visit?
Each visit has been different, though all broadly cover my work in long term monitoring of the weather, particularly climate and ozone measurements. I first visited Halley in 1982, when the base was in steel tubes underground, with the bunk room temperature below freezing. Since then the stations have steadily become more comfortable, so that some have shared en-suite bunk rooms. I’m here to supervise the move of our climate and ozone monitoring equipment to the new Halley 6 station. This should be more comfortable than the present station, though not to the extent of having en-suite rooms!
You’d just graduated from Cambridge University with a degree in natural sciences when you first visited Halley, what data were you working on when you determined the hole in the ozone?
The first visit was really to see what the station was like, and to install a new Dobson ozone spectrophotometer. I did a comparison against the existing instrument and showed that they gave the same results. This gave us confidence that it wasn’t an instrumental problem that gave the low ozone readings, and I then followed this up by showing that the readings were dropping systematically each spring.
What advantages does Halley have as an observational base over others in the Antarctic and how did this contribute to BAS publishing its results before NASA?
Halley is one of the longest running Antarctic stations, and moreover has a continuous record of ozone since 1956. We have used the same type of ozone measuring instrument throughout this period, although the actual instrument has changed every decade or so. The one from 1982 has been refurbished and is temporarily back at Halley to allow us to set up the ozone monitoring room at the new station. Other advantages that Halley has are that it is usually well within the circumpolar vortex that forms around Antarctica in the ozone layer during the winter. It is this region that sees the worst ozone depletion making it easier to spot changes. Halley is further north than the South Pole, so the sun rises earlier here, meaning that we can start ozone observations well before South Pole, who can’t start until the ozone hole is past its deepest.
Joesph Farman, Brian Gardiner, and Jonathan Shanklin of the British Antarctic Survey
The publication of your original ozone paper in Nature looks unassuming. Did you have any idea at the time of the global impact your discovery would have?
We never really expected an international treaty to be signed by every one of the UN member states! It was more an interesting scientific curiosity that confirmed predictions of ozone depletion due to CFCs, but in a completely unexpected part of the atmosphere.
What would’ve happened if provisions such as the Montreal Protocol were not implemented?
The Earth would be a lot hotter! The ozone destroying substances are powerful greenhouse gases and in fact the Montreal Protocol has done more than the Kyoto Protocol to combat the threat of global warming. In addition we would have much lower ozone levels on a global basis, and this would have significant impact on human health through increased UV leading to cancers, cataracts etc.
In your opinion, was public pressure or (inter)national policy more effective in changing the laws concerning CFCs?
It was a combination of things. First holes are bad and have to be filled in! The link between ozone and skin cancer was a powerful driver of public opinion. It was also relatively easy to find substitutes, so it did not require any change in lifestyle, and manufacturers were quite happy to create alternative products.
As I understand it, the hole will “heal” in 2080 or so. How can we avoid a repeat occurrence and will there be a “scar” or irreversible impact of the hole?
The amount of ozone depleting substances (ODS) in the atmosphere is slowly declining, and as they decrease so too will the size and depth of the ozone hole, though in any one year the actual size and depth will depend on meteorological conditions in the ozone layer. Although we are clearly past the peak of ODS, because of the meteorological variability it is still too soon to say that we have had the worst ever ozone hole. This year’s was in fact one of the worst and set records for size for some dates. By 2080 the level of ODS will be down to those of the mid 1970s, so in theory the last ozone hole will have been seen. The Montreal Protocol provides the best hope to prevent a recurrence, but some natural events could lead to widespread ozone depletion – perhaps a super-volcano going off or a giant meteorite exploding in our atmosphere such as happened over Tunguska in 1908. For many places the future world will see a thicker ozone layer, as although the surface of the earth will warm, the ozone layer will become colder with increasing levels of greenhouse gases. This will change the rate of chemical reactions involving ozone and give a slightly thicker ozone layer.
All the Antarctic research stations are conducting a variety of long term observations. Is it harder to get funding for these projects? Has the ozone hole discovery helped convince funders and the public of the importance of long term studies?
Long term monitoring was certainly threatened before we made the discovery, and it went a long way to securing better funding for such studies over the last 25 years. I sense that this is now coming to an end and that future funding is being squeezed. Without a good baseline however it will be much harder to confirm the damage that we are doing to the planet.
You mentioned in your Reflections on the ozone hole article of May 2010 that you swapped the axes and scale of the graph showing ozone loss against CFC concentration. Whose idea was this and do you think it increased the impact of your work?
I can’t honestly remember who did it that way, or even if it was particularly deliberate. It certainly made the result very convincing. Indeed the theory that Joe Farman proposed (involving gas phase chemistry) in the paper turned out not to be correct. Yes it was CFCs, but the process involved surface chemistry on the surface of stratospheric clouds, which usually are only widespread during the Antarctic winter. This March some did form over the Arctic, resulting in the lowest every Arctic ozone values.
Is this a common occurrence in science research?
I think sub-consciously everyone tries to make their graphs portray the results of measurements in an easy to understand way. Sometimes this is done by fitting curves to the data, and others it involves choosing the scales.
Professor John Shanklin’s current visit to the Antarctic in 2012 can be viewed here.
The Halley Research Station in its sixth reconstruction and is expected to be completed in all its mobile glory this month.
Photo credits: Podknox on Flickr, NASA and the British Antarctic Survey