by Katia Ferrante

MONACO.  The web headlines recently read like an international eco-thriller about the so named “Ozone Hole”. Last November NASA and NOAA scientists reported that 2019 Ozone Hole is the smallest on record since its discovery. And, according to a recently released UN-backed report, ozone-depleting substances are continuing to decrease more than three decades after a major international agreement phased out their production.

Scientists from NASA and NOAA work together to track the ozone layer throughout the year and determine when the hole reaches its annual maximum extent. This year, unusually strong weather patterns caused warm temperatures in the upper atmosphere above the South Pole region of Antarctic, which resulted in a small ozone hole.
Credits: NASA Goddard/ Katy Mersmann

In 1985 British scientists announced the discovery of a shocking decline in atmospheric ozone concentrations high above Antarctica. The “ozone hole,” as it became known, was caused by ozone-eating chemicals called chlorofluorocarbons (CFCs) used as refrigerants in air conditioners and propellants in aerosol spray cans. The discovery galvanized public opinion, particularly over concerns about the risk of skin cancer, cataracts, and sunburn associated with increased exposure to ultraviolet radiation. The world came together to fix it. Scientists and politicians persuaded the USA President Ronald Reagan and the then British prime minister, Margaret Thatcher, to take action. Although many uncertainties over the science remained—which were eagerly exploited by the chemical industry – Ronald Reagan and Margaret Thatcher, who had been a research chemist in her early life, recognized the danger posed by the ozone hole and vigorously backed international negotiations to ban CFCs, including CFC-11.

Margaret Thatcher and Ronald Reagan at Camp David in November 1986.Credit…Ronald Reagan Presidential Library/European Pressphoto Agency

Their vigorous leadership was crucial during the negotiations of a treaty. On January 1 1989, the Montreal Protocol on Substances that Deplete the Ozone Layer became law. Former UN secretary general Kofi Annan, said that it constituted one of the most successful international agreements ever seen.


It was a model of cooperation.

In his signing statement, Reagan heralded the Montreal Protocol as “a model of cooperation” and “a product of the recognition and international consensus that ozone depletion is a global problem.” It remains his signature environmental achievement. The success of the Montreal Protocol holds lessons for today’s efforts to confront human-induced climate change.

The protocol began modestly and was designed to be flexible so that more ozone-depleting substances could be phased out by later amendments. Developing countries were also provided with incentives and institutional support to meet their compliance targets.

But perhaps the most important lesson is the need for action, even when the science is not yet conclusive. “We don’t need absolute certainty to act,” says Sean Davis, a climate scientist at the US National Oceanic and Atmospheric Administration. “When Montreal was signed, we were less certain then of the risks of CFCs than we are now of the risks of greenhouse gas emissions.”

Several decades later, it’s hard to disagree. The 2019 Scientific Assessment of Ozone Depletion comes five years after the last report, showing trends continuing to head in the right direction. Concentrations of both total tropospheric chlorine and total tropospheric bromine have waned since the 2014 assessment. That massive hole we were worried about is also continuing to thicken. Outside of the polar regions, stratospheric ozone has increased by between 1 and 3 percent per decade since the year 2000. What this means is we can expect the layer of ozone covering the Northern Hemisphere’s mid-latitude will be back to 1980s levels sometime in the 2030s, and the South Pole Hole to more or less fade by the 2060s.


Those efforts still require careful monitoring, especially in the face of occasional illegal production of ozone-attacking pollutants. But the science does say we’ve accomplished one impressive U-turn. Over the years, the protocol has been amended in light of new scientific findings. In 2016, delegates came together in the Rwandan capital of Kigali to once again tweak its requirements, this time taking into account the global warming properties of hydroflourocarbons. In Kigali, delegates worked tirelessly day and night to negotiate and reach a deal on a timetable that would mandate countries to phase down the production and usage of hydroflourocarbons (HFCs). HFCs are man-made chemicals that are primarily used in air conditioning, refrigeration and foam insulation, and are powerful greenhouse gases that can be thousands of times more potent than carbon dioxide in contributing to climate change.

This time-lapse photo from Sept. 9, 2019, shows the flight path of an ozonesonde as it rises into the atmosphere over the South Pole from the Amundsen-Scott South Pole Station. Scientists release these balloon-borne sensors to measure the thickness of the protective ozone layer high up in the atmosphere.
Credits: Robert Schwarz/University of Minnesota

“The Montreal Protocol is one of the most successful multilateral agreements in history for a reason,” said the head of UN Environment, Erik Solheim. “The careful mix of authoritative science and collaborative action that has defined the Protocol for more than 30 years and was set to heal our ozone layer is precisely why the Kigali Amendment holds such promise for climate action in future.”

Following many years of continuous consultations, Parties to the Montreal Protocol struck a landmark legally binding deal to reduce the emissions of powerful greenhouse gases in a move that could prevent up to 0.5 degrees Celsius of global warming by the end of this century, while continuing to protect the ozone layer.

On the other hand, a new report by the Intergovernmental Panel on Climate Change (IPCC) suggests if we’re to have any hope of limiting global warming to a rise of just 1.5 degrees Celsius, we’ll have to act like we’ve never acted before.

“Limiting warming to 1.5 C is possible within the laws of chemistry and physics but doing so would require unprecedented changes,” said Jim Skea, co-chair of the IPCC Working Group II.

Next year the Kigali Amendment will be ratified, and signatories will be required to go back and work out how they’re going to cut back on the production and usage of yet another polluting gas.

Buoyed by signs of improvement on the ozone layer, we might have good reason to think this might be a boon for global warming. Closing that ozone hole was the warm-up exercise. The real test is yet to come, and failure really isn’t an option.


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