The ozone hole 25 years on: a budget cut nearly thwarted the discovery of the gaping ozone hole over the Antarctic, and it was revealed almost by accident, writes DICK AHLSTROM

YOU WOULD think that something the size of North America couldn’t possibly go unnoticed. But it did and remained hidden for many years before British scientists told the world a massive ozone hole had opened up over Antarctica.

That discovery reached the journal Nature25 years ago, in the process sparking an international effort to find a way to close the hole. The result was the Montreal Protocol, the most successful international treaty yet agreed.

The report in Naturein 1985 almost never arrived however. The device that recorded the data was there not to measure ozone but to help predict the weather. And it was nearly shut down as unnecessary when researchers from the British Antarctic Survey (BAS) faced cost cuts.

Yet the discovery was made and against the odds. “It was a whole string of coincidences and a lucky break for us,” says Jonathan Shanklin, who with group leader Joseph Farman and Brian Gardiner carried out the research that confirmed the springtime opening of a hole in atmospheric ozone.

Scientists during the 1970s were already aware that atmospheric ozone was being damaged. Concerns arose because ozone layers between 10km and 35km up are essential to protect us from 90 per cent of the sun’s harmful ultraviolet rays. Loss of ozone would leave us at much greater risk of skin cancers and cataracts, and so research was launched to assess the danger.

The US National Aeronautics and Space Administration had been flying ozone-measuring satellites over the Antarctic and other places too. One theory at the time held that ozone loss would occur not at the poles but in the tropics, says Shanklin. Although the satellites detected variability in Antarctic ozone levels, there was no pattern and so the satellite data did not ring alarm bells.

Experimental physicist Shanklin meanwhile had joined the BAS in 1977. "I had no background in meteorology and no preconceived ideas of how the atmosphere behaved," he writes in a special feature published this morning in Nature.

This allowed him to look with a completely unbiased eye at ozone records taken since 1957 at the BAS’s Halley research station.

BAS planned an “open day” for the public in 1983 and Shanklin was to review the Halley data. Initially he thought the data would “reassure the public”, showing that ozone levels by the mid-1980s were no different to levels from 20 years earlier.

He immediately saw however that levels during Antarctic springtime could be unusually low. The research team thought it might be because of weather variability but when they replotted the data it was obvious the decline in ozone was “systematic”, says Shanklin.

There was a consistent pattern, with large-scale losses in springtime ozone levels year after year.

They measured the losses at about 70 per cent down on the levels from the early 1970s, says Shanklin. They had identified the ozone hole. Then luck intervened, something that helped the BAS team get the discovery out first.

Shanklin wrote to the satellite ozone analysis centre at the University of California in Livermore, asking whether the satellites were also seeing this springtime decline. He got no answer and so wrote again but there was no reply. The team then published their results in 1985, capturing the distinction of being the first research group to do so.

Two years later the Montreal Protocol agreed an international phase out of the chemical cause of ozone depletion, CFCs. While governments accepted the need for a worldwide response to ozone loss, Shanklin does not believe an agreement on climate change will be as easy to achieve.

Defeating it will force unpalatable lifestyle changes and cost a great deal raising public resistance no matter its importance, he says.

The discovery of the ozone hole also tells another story, he believes. “What it demonstrates is how fragile our environment really is.” It took less than 20 years for humans to have this profound effect on the planet’s atmosphere.

“My worry would be for the future. Are there other tipping points that will cause problems in the future? We have got to follow the precautionary principle.”

dahlstrom@irishtimes.com

Twitter: @dickahlstrom