It seems unlikely that a coffin-sized machine that instructed its users to wrap it in a quilt to keep it warm could beat the most advanced NASA satellites to the discovery of one of the world’s greatest environmental crises.
Yet, in 1982, the Dobson meter, whose readings had to be sent by ship from the Antarctic to a team of researchers in the UK, revealed what those monitoring NASA’s satellites had apparently missed and what some scientists had long feared: a mysterious dip in ozone levels.
News that harmful gases accumulating in the Earth’s atmosphere had cleaved a large hole in the ozone layer shocked the world and led to fears of a worldwide spike in skin cancer.
Realising the danger that a hole in this shield presented, the world rallied and began to gradually phase out chlorofluorocarbons (CFCs), which contain the chlorine that harms the Ozone, under an international treaty known as the Montreal Protocol. The protocol has since been universally ratified by 196 nations and the European Union.
The result of this international effort is one of the environmental movement’s greatest success stories, highlighted by strong evidence published in the journal Science last week that shows the hole in the ozone layer is finally beginning to heal.
“This is a very positive story,” said Dr. David Fahey, Director of the Chemical Sciences Division at the US National Oceanic and Atmospheric Administration’s Earth System Research Laboratory, and a co-chair of the Scientific Assessment Panel of the Montreal Protocol. “The whole world has participated in the control of ozone-depleting substances. All the behind the scenes work has paid off. We are slowly reversing the trend.”
The role played by the Dobson Ozone Spectrophotometer – a delicate beast of a machine invented in the 1920s – cannot be underestimated. The odd readings it provided gave the world the first scientific evidence that CFCs, which were widely used in aerosols and refrigerators at the time, were rapidly accumulating in the atmosphere, ripping a large hole in the ozone layer. The potential consequences for the health of humans, animals and plants were devastating.
The ozone layer acts as a protective shield that blocks most of the sun’s high-frequency ultraviolet rays, which can cause skin cancer and cataracts in humans and trigger reproductive problems in fish, crabs, frogs and even phytoplankton.
With Thursday’s news that the Ozone layer is starting to heal, scientists say it is clear that this phase out of ozone-depleting substances is working.
“A best estimate is that about half of the healing is due to Montreal Protocol bringing changes in chlorine,” said the author of the last week’s research paper, Professor Susan Solomon of MIT. The other half of the healing may be caused by seasonal meteorological changes over Antarctica although scientists say that more research is needed to determine the cause of these variations.
Prof Solomon and the scientists behind the latest findings say that the hole shrunk by an area about the size of India between 2000 and September 2015 – roughly four million square kilometres in 15 years. The researchers say that, while other studies have shown the declining abundance and influence of CFCs on the ozone layer, this new study is the first to show “the first fingerprints of healing”; that the ozone layer is actually starting to grow again.
To date, more than 98 per cent of chemicals that thin the ozone layer – about 2.5 million metric tonnes – have been phased out globally under the Montreal Protocol, which is the first universally ratified treaty in the history of the United Nations. As a result of this reduction, the Antarctic ozone hole is expected to return to pre-1980 levels by around the middle of this century.
One of the key substitutes that have been replacing ozone-depleting substances is hydrofluorocarbons (HFCs), a group of chemicals that have high global warming potential. These so-called “super greenhouse gases” are mainly used in refrigerators and air conditioning units. The parties to the Montreal Protocol have agreed that they will work within the Montreal Protocol in 2016 to an HFC amendment by first resolving challenges and generating solutions. .
An HFC phase-down would avoid 0.4°C of warming by 2100 – a crucial contribution to climate change mitigation and to the implementation of the Paris Agreement to hold global temperature increase this century below the agreed dangerous limit of 2°C.
“The success of efforts to heal the ozone layer provides some really direct encouragement to a world facing multiple environmental problems,” said Dr. Fahey. “It means that there is hope that the world can act together as a group and fix the next big problem – climate change.”