Cause and Effect | How the Montreal Protocol paved the way from climate crisis to climate action
The groundbreaking agreement signed in 1987 has played a pivotal role in addressing the depletion of the ozone layer caused by ozone-depleting substances
September 16 marked 36 years since the Montreal Protocol came into effect. The day is observed as World Ozone Day, signifying the success of the only climate treaty ratified by every country in the world.
The Protocol, signed in 1987, is a "landmark multilateral environmental agreement" that helped regulate the consumption and production of nearly 100 man-made chemicals -- ozone-depleting substances (ODS).
The protocol was not only one of the earliest steps taken to address the “triple planetary crisis of climate, nature and pollution”, it also marked a turning point in environmental history.
Speaking of the role it has played in climate action, Meg Saki, executive secretary of the United Nations Environmental Programme's Ozone secretariat, said in 2021, "When sound science is the basis for universal action, we can overcome what may seem insurmountable global environmental challenges.”
What is the Ozone layer?
First, the science of it.
The Earth’s atmosphere is composed of several layers. The lowest, troposphere, extends from the Earth’s surface up to about 10km in altitude. For reference, Mt Everest is only about 9km high. So, all of human activity is happening in this layer.
The next is the stratosphere, which continues from 10km to about 50km. For reference, most commercial planes fly in the lower part of the stratosphere.
Most atmospheric ozone — a naturally occurring gas comprising three oxygen atoms — is concentrated in a band in the stratosphere, some 15-30km above the Earth’s surface.
Now for better understanding: The stratospheric ozone forms a gas shield acting as a natural sunscreen for all life forms on the Earth against ultraviolet radiation.
How did it gain attention?
In the mid-1970s, scientists issued a warning that chemicals in everyday products like aerosols, foams, refrigerators and air conditioners were harming the ozone layer. The scale of the problem was unknown at the time.
The emergence of the hole was confirmed when a team of scientists in 1987 flew a Nasa research aircraft into the hole.
On September 16 that year, as the scientists analysed data, they saw that as a chemical called chlorine monoxide increased in the Antarctic stratosphere, ozone decreased.
This provided conclusive evidence that chlorine monoxide and chlorofluorocarbons were causing the ozone hole.
“The world's natural sun shield, which protects humans, plants, animals and ecosystems from excessive ultraviolet radiations, had been breached," the United Nations Environment Programme said in a dramatic recollection of the tumultuous 1980s.
Its impact was nothing short of dramatic.
The ozone layer blocks the Sun's UV radiation, not just the kind that sunscreen commercials would have you protect yourself from. But also the kind that damages all living tissue causing skin cancers, cataracts, and damaging plants and crops and ecosystems.
“If there were no ozone layer, the Sun would sterilise Earth’s surface,” said Paul Newman, chief scientist for Earth Sciences at Nasa’s Goddard Space Flight Center. Newman was among the scientists who proved the role of CFCs in ozone depletion.
What happened next?
Governments had already adopted the Vienna Convention for the Protection of Ozone Layer in 1985, when the issue was first flagged. This provided a framework for the Montreal Protocol.
While Nasa’s data would not be published until later, by the end of that momentous day in 1987, 27 nations had agreed to the Montreal Protocol on Substances that Deplete the Ozone Layer.
“It was basically signed without knowing for sure what was causing the Antarctic ozone hole,” David Fahey, director of NOAA’s Chemical Sciences Laboratory and co-chair of the Montreal Protocol’s scientific assessment panel who was among the scientists, told Scientific American.
The protocol came into effect in 1989 and by 2008, it was the first and only UN environmental agreement to be ratified by every country.
The results have been equally dramatic.
In January this year, the UN-backed Scientific Assessment Panel to the Montreal Protocol on Ozone Depleting Substances quadrennial assessment report, published every four years, said that the phase-out of nearly 99% of banned ODS was successful, with the Ozone layer expected to recover to 1980 values by around 2066 over the Antarctic, by 2045 over the Arctic and by 2040 for the rest of the world.
What was the climate impact?
The Ozone Treaty was signed at a time when developing nations were just acquiring a lot of the technology that had already thrived in the West, particularly air conditioners and refrigerators. The treaty then helped prevent a further surge of super-pollutants into the atmosphere.
A study in 2007 showed that without the Montreal Protocol, CFCs would have had a greenhouse gas content nearly equal to half the carbon dioxide emissions from all other sources by 2010.
“I think the estimates are something on the order of an extra 2 degrees by the middle of the century,” Susan Solomon, a professor of environmental studies at the Massachusetts Institute of Technology, told Scientific American.
The next steps.
Faced with new risks, the Protocol has been updated. In 2016, the Kigali Amendment was adopted to phase down hydrofluorocarbons, potent greenhouse gases often used as replacements for the banned ODSs in refrigerators and air-conditioners.
The Scientific Assessment Panel said the amendment is estimated to avoid an additional 0.3-0.5 degree Celsius of warming by 2100.
The amendment has been ratified by 152 countries so far.
In a first, the Scientific Assessment Panel also examined the impact of the intentional addition of aerosols into the stratosphere, known as stratospheric aerosol injection (SAI).
A geoengineering process, SAI has been proposed as a potential method to reduce warming by injection sulphate aerosols in the atmosphere to reflect the sunlight back, thereby reducing the amount of heat that enters the troposphere.
But, according to the panel, this method “could also affect stratospheric temperatures, circulation and ozone production and destruction rates and transport”.
The unique success of Montreal.
The Montreal Protocol was not only signed at a time when the real cause of ozone depletion was not conclusively known, but it is also an agreement whose success has not been replicated in any other climate treaty, regardless of the urgency.
At the last COP summit, experts and activists again left the venue disappointed at the toning down of language on fossil fuels. As they did after the recently concluded G20 Summit.
Scientists involved with the Montreal Protocol have said that all other agreements rely on voluntary commitments with no penalties for breaking them.
Montreal is universal with 197 member countries, legally binding with penalties for countries that flout provisions, and it is fully funded, providing assistance to poorer countries that might not have been able to meet targets.
As a prime example, British Prime Minister Rishi Sunak is considering weakening some of his government’s key commitments for a “more proportionate” net zero by 2050.
“Our success in phasing out ozone-eating chemicals shows us what can and must be done – as a matter of urgency – to transition away from fossil fuels, reduce greenhouse gases and so limit temperature increase,” said WMO Secretary-General Prof Petteri Taalas.