How do we recover the ozone layer, and what does it teach us to fight global warming


In 1985, the world was facing a major environmental crisis. After years of studies, scientists warned that the ozone layer was becoming more fragile and in danger of disappearing.

The ozone layer is an area of ​​the stratosphere that absorbs between 97% and 99% of the Sun’s high-frequency ultraviolet radiation – which can cause a lot of harm to living beings. The layer is between 15 km and 50 km in altitude and contains 90% of the ozone present in the atmosphere.

After the warning that the layer was so fragile that there were “holes” in some parts of it, the world went into alert – and a series of actions unprecedented in history were taken.

Governments signed the Montreal Protocol, considered a milestone in environmental protection. But more than signing the agreement, governments, scientists, world leaders and companies actually put the measures into practice and worked together to ban chlorofluorocarbons (CFCs), chemicals that were depleting the ozone layer.

Since the protocol’s entry into force on January 1, 1989, CFC emissions have dropped to minimum levels.

In 2018, NASA announced that the amount of ozone-depleting chemicals was decreasing and that it was recovering.

How was this success possible? And most importantly, is it possible to reach a similar agreement to contain climate change?

“What’s interesting is how hundreds of nations involved in the protocol came to actually implement an agreement that was convenient for everyone,” says Carlos Méndez, vice president of the UN Intergovernmental Panel on Climate Change (IPCC).

However, the process of saving the ozone layer was not an easy one. Since scientists discovered that CFCs interacted with ozone and destroyed the ozone layer in the atmosphere in 1974, there has been much reluctance on the part of the chemical industry.

What can we learn from the history of the Montreal Protocol?

scientific evidence

In 1973, Mexican chemist Mario Molina joined Professor Frank Sherwood Rowland’s working group at the University of California, USA.

Molina’s chosen line of research was the impact of CFCs, chemical substances that accumulated in the atmosphere but were believed not to cause significant effects on the environment.

At first, the research didn’t seem particularly interesting. Molina focused on what could destroy CFCs in the atmosphere, but nothing seemed to affect them.

Until he discovered that the sun’s ultraviolet rays can break down CFCs, releasing chlorine and triggering a chemical reaction that destroys ozone in the atmosphere.

If the ozone layer weakened, ultraviolet rays would reach the Earth’s surface without any kind of filter, multiplying cases of skin cancer, eye problems and causing irreversible damage to the environment.

It was then that Molina and Sherwood realized the magnitude of the problem. They published their findings in the scientific journal Nature in June 1974 and shared the results not only with scientists but also with politicians and through the press.

As today, there were skeptical people who questioned the scientific evidence and predicted economic ruin. CFCs were everywhere: they had very useful applications in a wide variety of everyday objects and processes.

Popular for their low toxicity, practicality and price, CFCs were used primarily in the refrigeration industry, in refrigerators, freezers, air conditioning systems, aerosols and heat insulators. Its main prosecutor, chemist Thomas Midgley, died thinking he had done mankind a great favor.

According to David Doniger, strategic director of the US Natural Resources Defense Council’s Clean Energy Program, the way CFC makers reacted to the news is much like the oil and coal industry’s reaction to global warming.

They have acted against changes they may contain to contain the environmental tragedy by questioning science, attacking scientists and predicting economic disasters.

But by 1985 the evidence of harmful effects on the ozone layer was so great that measures were taken.

The studies by Molina and Sherwood were followed by those by Joseph Farman, Brian Gardiner and Jonathan Shanklin of the British Antarctic Survey, who found that there was a hole in the ozone layer at the south pole.

Molina and Sherwood won the Nobel Prize in Chemistry in 1995 for their findings related to the subject.

political will

“Every new information that comes out confirms that the ozone layer is being damaged by CFCs and other chemicals, and that if we don’t slow down and reverse this process, our health and way of life will suffer,” said British Prime Minister Margaret Thatcher during the 1990 London Ozone Layer Conference, just over a year after the Montreal Protocol entered into force.

“The Montreal Protocol was a historic achievement,” she continued. “It provided the first real evidence that the world was willing to cooperate to solve major environmental problems. And it was a big step forward.”

Even the then president of the United States, Ronald Reagan, whose government showed no interest in environmental issues, ended up accepting the scientific evidence.

Countries have gradually begun to phase out CFCs and replace them with other less ozone-depleting chemicals. There was no quick and easy solution.

Even part of the replacements for CFCs are hydrofluorocarbons (HFCs), which are less harmful to the ozone layer, but contribute to the greenhouse effect, which causes global warming and climate change.

Greenhouse gases accumulate in the Earth’s atmosphere and absorb infrared energy from the Sun, contributing to the increase in the planet’s global temperature.

Despite this problem, in terms of its main objective – recovering the ozone layer – the global effort was a great success.

In 1988, total emissions of substances that deplete the ozone layer reached their highest peak: 1.46 million tons. The following year, total releases dropped to 1.41 million tonnes. And in 2000 they were already at 260 thousand.

Researchers estimate that by 2030 the ozone layer will have fully recovered in mid-latitudes and by 2050 in the southern hemisphere. In the polar regions, it should be fully recomposed by 2060.

“The Montreal Protocol is one of the most successful multilateral agreements in history for one reason: its careful combination of science and collaborative action established to heal our ozone layer,” said Erik Solheim, executive director of the United Nations Program for the Environment, in 2018 .


The Montreal Protocol demonstrated that nations can unite in a common goal for the benefit of all. So why is it taking so long to reach a similar deal to contain climate change?

The planet failed to reduce CO emissions2, despite international agreements such as the Kyoto Protocol, whose objective was to reduce the emission of six greenhouse gases.

The Kyoto Protocol was signed in 1997 and entered into force in 2005, but its objectives have not been met.

In fact, documents leaked last week and to which the BBC had access show strong lobbying by some countries to change an important scientific report on how to deal with climate change before the 26th United Nations Conference on Climate Change (COP26), which will be held in November 2021 in the city of Glasgow, Scotland.

Countries are expected to make significant commitments to contain climate change at the summit. It’s the only way to keep global warming at 1.5°C – above that, the consequences are even more serious.

However, the leak revealed that Brazil, Saudi Arabia, Japan, Australia and Argentina are among the countries that have asked the UN to minimize the need to quickly stop using fossil fuels.

For Méndez, there is a fundamental question to understand why it has been so difficult for us to reach an agreement: the planet’s current economy and way of life derives in large part from the burning of fossil fuels.

“We see that, in the case of climate change, these gases (of the greenhouse effect) are involved in a series of processes that define the current way of life on the planet”, he says.

“This greatly increases the complexity, especially the economic implications,” emphasizes Méndez. In that sense, the Montreal Protocol was much easier. CFCs were produced by very specific chemical companies that reached replacement agreements with governments.

Doniger explains that there must be a transition period to move from burning fossil fuels to a greener economy, similar to that of CFCs to the chemicals that have replaced them.

“We can’t banish overnight. We need to transition,” he says.

“It will be more difficult to regulate fossil fuels, but the dynamics are the same.”

In this transition process, there may not be a single consensus. In this transition period, he emphasizes, it will be necessary to see how each country can contribute.

“Developed countries are the ones that emit the most (greenhouse gases), but they are more prepared to fight climate change than developing countries,” he says.

“There has to be a transfer of technology from developed countries to the poorest so that together we can fight climate change. But for that we will have to bear the costs.”

“This is perhaps the most important thing we’ve learned from Montreal. Nations had the political will to shoulder the cost and ban CFCs. It’s the kind of will we need for climate change.”


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