Scientific data reveal startling atmospheric changes.
A small team from the British Antarctic Survey (BAS) published a paper in the scientific journal Nature in May 1985 that led to significant changes in our management of planet Earth. The story begins in the previous decade.
I went to school at King's School, Chester, then a direct grant school, and one where pupils were pushed to study hard. This preparation took me to Magdalene College, Cambridge to read Natural Sciences. I specialised in experimental physics, with practical classes and lectures at the Cavendish Laboratory. Here I was taught to look at data with an unbiased view and both school and university were instrumental in preparing me for what was to come. A third strand was ringing church-bells in the mathematical patterns of change-ringing. This requires the ringer to quickly pick out patterns, something that also applies to scientific data.
Having completed my university course, my maths wasn't good enough to follow my dream of becoming a professional astronomer, so instead I took a one-year teacher training course to teach physics. The requirement of having to teach the same syllabus to pupils of whatever ability rather put me off teaching, though the training proved useful when it came to communicating the science of ozone and climate change to a wider audience.
I saw an advert for the British Antarctic Survey, who sought a physicist with an interest in meteorology and programming skills in Fortran. I ticked the boxes and was called up for an interview. I was number two on the shortlist, but fortunately (at least for me) the first person turned down the job offer. The job initially involved quality control of meteorological data coming back from the Antarctic, quality control of solar intensity measurements and processing the ozone data. Some of the quality control for the meteorological data had been automated by my boss, using computer programs he had written in a language called IMP on a PDP11 computer. The computer lived in a large air-conditioned room and was less powerful than the average mobile phone of today. The program would throw up checks, I would query the Antarctic observers via telex, using abbreviations similar to texting as there was a tight limit on the number of characters you could use. They would often come back disagreeing with the check, so I kept pressing for the chance to go to Antarctica to see for myself.
In the meantime I was also writing programs to start processing all the ozone data. Measurements from the Dobson ozone spectrophotometer at the Antarctic stations were written down on sheets of paper. Calculating an ozone amount from the measurements using log tables and a slide rule would take 10 minutes or so, and with up to a dozen measurements being made every day, quite a backlog had built up.
My first task was to supervise two colleagues who were digitising the records on the sheets. The quality control for this showed several common issues: the Antarctic observers might have written down the wrong time or type of observation; the digitisation team might have jumped columns on the sheets and occasionally there was an error in the measurements. Even with the obvious things corrected there were still occasional problem observations and it wasn't until some 30 years later that I finally discovered the cause. Many people are slightly dyslexic and swap pairs of numbers when they write them down, for example 1101 became 1011.
In parallel with this, I was writing computer programs that would calculate the ozone amount from each observation. The Dobson instrument makes solar intensity measurements at two wavelengths of ultra-violet light. One wavelength is strongly absorbed by ozone in the atmosphere and the other only weakly absorbed. Knowing the ozone observation coefficients and the elevation of the Sun (a calculation of three-dimensional trigonometry), the amount of ozone necessary to cause the difference in intensities can be calculated. In addition, the exact calibration of the instrument needs to be determined and this is found on sunny days by taking measurements at different times of day. If the instrument is well calibrated, the measured amount of ozone during the course of an average day should be constant. If it appears not to be, then the calibration values may need adjustment. After much refinement consistent ozone measurements were available, but there was still a backlog to work through.
About this time we were going to have an open day at the Cambridge headquarters to show the latest Antarctic science to eminent scientists, politicians and the public. There had been concern in the scientific journals that exhaust gasses from Concord, or chlorofluorocarbons (CFCs) from spray cans, might damage the ozone layer.
Being a naïve young scientist with a physics background I thought this unlikely, so decided to present that years' data and compare it with values my boss had computed from a decade earlier. I expected them to be the same, so Concord would be able to keep flying and the public could keep using their spray cans. The only problem was — they weren't the same. My boss thought that this might be a one off, but I wasn't sure. This provided an impetus to continue working up the backlog, but it was slow progress and in the meantime I got my chance of a visit to Antarctica.
Halley Station is on a floating ice-shelf some 100 metres thick
There were two aims of the trip: to install a brand new Dobson instrument at Halley Station and compare it against the existing one, and to get a feel for the weather observing at all the stations. I left England in mid-December 1981 and spent Christmas in the Falkland Islands. One highlight was the Boxing Day races at Stanley, where there were more land rovers in one place than I'd ever seen before. From the Falklands our ship sailed first to South Georgia, then back to the Falklands before finally heading south towards Halley Station. Seeing the first icebergs and then 'ice-blink' in the sky from the pack-ice on the horizon was quite a thrill and made me wonder what early explorers must have thought when they encountered these phenomena for the first time.
Halley Station is on a floating ice-shelf some 100 metres thick, which is buffered by a stretch of 'fast ice' of frozen sea-water attached to it. We were offloaded onto the fast-ice, then travelled in an open sledge up to the top of the ice-shelf, which sticks up some 30 metres above the 'fast ice'. From there we transferred into a sno-cat for the ride of some 15 kilometres to Halley Station. Our stay was a short one, so I had to cram in all the comparisons between the old and new Dobsons, as well as get a feel for the routine meteorological work. All too soon it was time to leave and head back to the Falklands and then north to Mar del Plata, an Argentine port and naval base.
Some of my colleagues headed back to Cambridge, but I stayed on board the Royal Research Ship Bransfield for the second part of my trip to visit Faraday and Rothera stations on the coast of the Antarctic Peninsula. This was originally intended to be a relatively short trip, but I persuaded my boss that it would be useful to spend some time at Faraday in order to become really familiar with the station routine and the range of weather conditions experienced. So having crossed the Antarctic Circle to get to Rothera, I returned to Faraday and stayed there whilst the ship headed towards Punta Arenas to collect supplies and a member of the wintering team at the station.
By now it was late March, and we were hearing concerns about the political situation between Great Britain and Argentina, though having just visited Argentina we could scarcely believe it. On 1 April the station radio operator woke us early to say that Stanley radio in the Falklands was broadcasting news of an invasion and playing patriotic music. We heard the invasion proceed live, with the sound of shells arching over the town towards the Marine's barracks a few miles away. Eventually the station was closed down, but we could still contact some of the Falkland islanders using amateur radio.
Eventually the Bransfield sneaked out from Punta Arenas and came back to Faraday to collect me, travelling on to Signy Station and finally heading towards South Georgia. The UK military persuaded the captain that it wasn't helpful to rescue the British scientists, so we then sailed all the way up the middle of the Atlantic, docking next to the QEII in Southampton. A few days later she sailed, doing the journey that had taken us a month in just 10 days. It was wonderful to see the green of early May in England, a colour that is largely lacking from Antarctica and the Atlantic Ocean.
With this experience behind me I continued work on reducing the ozone data and I worked backwards in time until I had finished all the backlog. When I plotted the minimum springtime ozone amount on a sheet of graph paper the conclusion was clear — there was a systematic decline in the amount of spring ozone and it certainly wasn't a one-off. I then wrote up the work in a draft paper, and plonked it on the desks of my bosses (and their boss). The top boss came back with lots of suggestions for improving the paper, and clouds of tobacco smoke emerged from my pipe-smoking boss's door. Eventually he came up with a possible chemical mechanism to explain the observations, something that he thought essential for a paper to appear in 'Nature'. Around Christmas 1984 the paper was in a fit form to send off to 'Nature', who accepted it and it was published in May 1985.
the ozone hole was forming over Antarctica because of CFCs and … the atmospheric conditions
It provided a considerable shock to the world. The theory then prevailing had suggested that if ozone depletion was to happen because of CFCs, it would start at high altitude over the tropics. The American satellite operators went back to their data and said: "Yes there is a large hole in the ozone layer over Antarctica". They had missed it, in part because they hadn't looked at the data their quality control system was rejecting, in part because they hadn't taken any note of a letter that I had written to them, and in part because the computer technology of the 1980s didn't have the graphics visualisation capability that we take for granted today.
Very quickly the scientific community mobilised its resources and found that the ozone hole was forming over Antarctica because of CFCs, and specifically because of the atmospheric conditions during the Antarctic polar winter. Antarctica is a mountainous continent surrounded by open ocean, and the wind system in the ozone layer between about 14 and 20 kilometres is relatively simple. Over Antarctica the air in this part of the ozone layer cools below -78°C during the winter, and clouds form in it. On the surface of the clouds chemical reactions take place, converting the chlorine from the CFCs into an active form, which breaks down ozone when the sun comes back in the spring. The ozone depletion only happens where these clouds are present. In the north the Arctic Ocean is surrounded by mountainous continents, which give rise to a more complex wind system, with winter temperatures in the ozone layer on average about 10° warmer than in the Antarctic. That is all the difference needed to make ozone depletion over the Arctic a relatively rare phenomenon.
Our discovery and the confirmation that the culprit was indeed the CFCs quickly led to the Montreal Protocol, which seeks to limit the introduction of ozone depleting chemicals into the atmosphere. It has proven to be remarkably successful. Every UN Member State has signed up, and the treaty is working. The amount of ozone depleting material in the atmosphere is going down, but it will be another 50 years or so before we finally have the last ozone hole. Recovery may be slowed by unauthorised release of ozone depleting chemicals as was shown by the recent discovery of a slow-down in the rate of decline, linked to the use of CFCs in building insulation foam in China.
Recovery over Antarctica is also likely to be slowed by what else we are doing to the atmosphere with the introduction of gasses such as carbon dioxide and methane. Whilst these act to warm the surface of the Earth, higher up in the ozone layer they produce a drop in temperature and hence make the clouds more likely to form. Events outside our control may also play a part, whether it is a massive volcanic eruption or a giant meteor strike, either of which could affect the ozone layer.
Every year since our discovery an ozone hole has formed over Antarctica during the spring. Whilst it mostly stays over Antarctica and is circular, sometimes it becomes elliptical and can stretch north far enough to cross the tip of South America and the Falkland Islands. As summer comes, the air warms, the stratospheric clouds disappear and the ozone hole fills in. The hole has never extended as far as Australia and New Zealand, but the ozone layer over the Pacific does thin as a consequence of the ozone depletion over Antarctica. In addition, the Earth is closer to the Sun in the southern summer than it is in the northern summer, so inhabitants of the Southern Hemisphere receive a greater exposure to ultra-violet light and thus experience a greater risk of skin cancer.
In many ways the problem of the ozone hole was relatively easy to solve. The name 'ozone hole' gave a graphic description of the phenomena and there is a perception that holes need to be filled in. With a thinning ozone layer there was the risk of greater exposure of people to ultra-violet light and hence a greater risk of skin cancer. These points were enough to make it a concern to voters. In parallel, industry was very willing to produce alternative chemicals and so there was no need for a change in lifestyle if CFCs were phased out. In addition there was strong political support from the top, as Margaret Thatcher was trained as a chemist and therefore understood the science. Greenhouse warming is very different — it sounds pleasant and dealing with it and all the other environmental issues that face us will require changes in lifestyle.
climate change … is only one of many symptoms that affect our planet
The discovery of the ozone hole presents several lessons, which are often ignored in today's political climate. There is the need for continuous long-term monitoring of our planet — its atmosphere, land, oceans and living things so that we know what is changing. There is a need to listen to the scientific evidence and act upon it — it is not always black and white, but the balance of probability should be biased towards the precautionary principle of 'doing no harm'. The rapid appearance of ozone depletion over Antarctica gave clear evidence of how quickly we can change our environment — it only took 10 years for the ozone layer to go from normal to one third depleted.
Today the focus is on climate change, but this is only one of many symptoms that affect our planet. Just as when a doctor treating a patient considers all the symptoms before deciding on the underlying cause, so too must we. The ozone hole, climate change, ocean plastics, soil degradation, water shortages, decline in biodiversity and many other symptoms have one underlying cause — ourselves. If we aspire to retaining our beautiful planet we must change, otherwise we are likely to be changed.
The National Library of Scotland has significant collections of science publications, covering the subject of science about environmental change and ozone layer depletion. We also subscribe to numerous scientific eResources including Brill, Karger, SpringerLink, and Web of Science. To read more about polar history, the Library's mountaineering and polar collections contain material relating to the Antarctic at the start of the 20th century.