Joe Farman had only ever published a handful of research papers. He was one of the foot soldiers of science, running instruments monitoring the atmosphere above the UK’s Halley Bay research base in Antarctica. But one of his rare excursions into print is among the most famous by an environmental researcher. In October 1983, Farman discovered that a huge hole had opened up in the ozone layer over Antarctica – and that it was man-made. , they caused a sensation – and major embarrassment at NASA. For while NASA’s satellites had been monitoring ozone levels around the world 24/7, Farman had found the hole with an ageing instrument wrapped in a quilt. Twenty-five years on, NASA has challenged the accepted version of events. So what really happened?
IN THE early 1980s, scientists thought they understood the ozone layer – and they thought its future was secure. Fears that CFCs and other synthetic chemicals might be eating into the ozone layer seemed unfounded. In 1984, the US National Research Council reported that rates of ozone loss were less than anticipated – fractions of 1 per cent. “The ozone layer isn’t vanishing after all,” proclaimed The Wall Street Journal that year. Many environmental groups seemed to agree and dropped the issue.
Enter Joe Farman, chief atmosphere-watcher at the British Antarctic Survey (BAS). While others thought the panic over CFCs was over, he was increasingly alarmed by data coming from one of his prize instruments. His 25-year-old Dobsonmeter calculated the thickness of the ozone layer by measuring ultraviolet radiation penetrating the atmosphere and it showed that ozone levels had dipped sharply for several weeks in October 1982. Then, in October 1983, says Farman, “it just went haywire; the levels really fell away”. Half the ozone layer had vanished.
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Fearing his ageing Dobsonmeter might be on the blink, Farman sent out a replacement. But by October 1984, the new one was showing an even deeper hole. When Farman’s findings finally appeared five months later, they caused a sensation, especially Farman’s suggestion that the hole was not natural but the result of ozone-destroying reactions triggered by CFCs in the stratosphere.
The following year, a research plane flew through the hole and detected the reactions Farman predicted were taking place on the surface of frozen particles in stratospheric clouds over the South Pole. This discovery led directly to the tough new rules on CFCs and other ozone-eating chemicals agreed at Montreal in 1987 – the Montreal protocol.
Farman’s success was the result of brilliant intuition and dogged research. He had been quietly measuring the ozone above Halley Bay since he first took the Dobsonmeter south during the International Geophysical Year in 1957. Farman’s triumph was a significant blow for NASA, though. With satellite instruments monitoring ozone levels round the world 24/7 and archiving 140,000 readings a day on magnetic tape back at NASA HQ, why hadn’t its researchers spotted the hole?
In a radio interview a couple of years later, NASA’s Richard Stolarski explained that although NASA’s satellite monitors revealed very low ozone levels across Antarctica, software analysing the data dumped the low readings as obviously false. For years, that was the accepted version of events. Today, however, . Richard McPeters, one of NASA’s ozone scientists back in the 1980s and still on the team, gives his account of what happened on NASA’s website. “It makes a great story to talk about how NASA ‘missed’ the ozone hole, but it isn’t quite true. In 1984, before publication of the Farman paper, we noticed a sudden increase in low values from October 1983. We had decided that the values were real and submitted a paper the following summer when Joe’s paper came out, showing the same thing.”
“NASA’s software dumped the low ozone readings as false”
The implication is clear: Farman may have published first, but NASA knew what was going on all along. “We were right behind him,” McPeters told 91av. But that is not how the British remember it. “It’s all a long time ago, but I have never heard anyone from NASA who was actually involved claim they knew anything before I pointed it out,” says Farman. “Some of the people who came later now say they found the ozone hole first. But it’s simply not true.”
So what really happened? According to Pawan Bhartia, who was processing the satellite data, strictly speaking NASA is right to say its software didn’t destroy the data. What it did was “flag it up” – identifying it as unreliable. The computer, he told 91av, then substituted “fill values” that it thought more likely. The effect was the same: the “unreliable” data was buried and the researchers had no reason to think anything was amiss. They might have re-examined the raw data sooner but for a second mishap. NASA had its own Dobsonmeter at the South Pole, which had been recording low ozone levels in 1983. But in what Bhartia calls “a clerical error”, the data was misread.
The British say NASA missed another opportunity to spot that something odd was happening above Antarctica when Jonathan Shanklin, Farman’s colleague at the BAS, wrote to two NASA contacts in late 1983 about the British team’s startling measurements. “I didn’t receive any reply that indicated that they had even looked at the data we were sending them,” he says. According to Bhartia, the data never reached his team.
It was only in September 1984 that NASA researchers first realised ozone might be disappearing over Antarctica – a year after its Nimbus satellite recorded the drop in ozone. At a conference in Greece, they heard Japanese researchers report low ozone values from their Antarctic Dobsonmeter. After that, Bhartia recalls, weeks of frantic checks at NASA finally revealed that “data over large areas of Antarctica were being discarded” and that the low ozone readings were “real”.
Now NASA made another error. Extreme meteorology was known to make spring ozone levels over Antarctica extremely variable. “We thought the low ozone readings were an intensification of this phenomenon,” says Bhartia. So still no alarm bells. It was only when Farman’s paper finally appeared in May 1985 that the penny dropped: the ozone hole was not a natural phenomenon. “Farman was the first person to recognise that what was happening may be related to chlorine chemistry,” says Bhartia.
NASA had only been collecting ozone measurements for five years, so it was understandable that its team took a while to realise the annual ozone thinning was increasing. But Farman, who had been taking measurements since 1957, realised something dramatic was happening, and that it couldn’t be blamed on the local weather. Finally, and most crucially, he was also the first to imagine the chemistry of what was happening. “It was a brilliant analysis, and has turned out to be essentially correct,” says Bhartia.
Without Farman, the truth might not have been discovered for several years or more. But he couldn’t have done it without his trusty Dobsonmeter, first assembled in a shed outside Oxford more than 50 years earlier by another dogged researcher, .
The odd thing about the Dobsonmeter is that for a quarter-century it was an instrument without much use. It finally came into its own during the International Geophysical Year of 1957, when researchers decided to make global measurements of the ozone layer. They put in an order for around 50 Dobsonmeters with the London instrument maker, R. & J. Beck.
Farman remembers going to Oxford to pick up his machine from Dobson in 1956. “Even after 25 years, they hadn’t completed the instruction manual,” he recalls. “That only arrived the following year.” Farman still has his original copy. For best results, it recommends wrapping a quilt round the instrument to keep it warm.
Only about 120 Dobsonmeters were ever made, of which some 50 remain in use. Each is known by its number. Dobson’s original, No 1 (far left), is in London’s Science Museum. Farman made his discoveries with Nos 37 and 51. Probably the oldest still in use is No 8, now 73 years old and sitting on the roof of the Norwegian Polar Institute in Svalbard. Dobson died in 1976, so he never saw his instrument’s finest hour.
The ozone hole still forms above Antarctica each austral spring. The Montreal protocol and its successors have drastically reduced the ozone-eating compounds reaching the stratosphere, but healing the hole is proving a slow process, says Farman, because the greenhouse effect increases stratospheric cooling by trapping more heat near the Earth’s surface. So there are no plans to retire the Dobsonmeters yet. And we’d probably be well advised to keep a few researchers like Farman – dogged, unspectacular and unfashionable – just in case.
