Saving the ozone layer has also reduced global warming

In 2003, Kofi Annan, then Secretary General of the United Nations, defined the Montreal Protocol as “perhaps the most successful international environmental agreement so far”.

Created in 1987, this treaty decreed the elimination of substances that deplete the ozone layer (ODS), a total of 96 chemicals used in aerosols and refrigeration, that were causing a hole in the stratosphere layer that protects the Earth from ultraviolet rays.

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• The ozone layer begins to recover

The Montreal Protocol was signed to protect life on Earth and human health as well, since the UV rays that this layer protects us from can cause skin cancer. Now, a joint study of scientists from the United Kingdom, New Zealand and the United States reveals that the treaty has also played a vital role in the fight against climate change and has slowed down global warming. Protecting the ozone layer has prevented ultraviolet radiation from damaging the tissue of our planet's trees and plants, limiting photosynthesis and, therefore, the biosphere's ability to absorb tons of carbon dioxide from the atmosphere. The study has been published in the prestigious journal

, with climate scientist Paul Young (Lancaster University) leading the investigation: “The conclusion of the study is that, at the end of this century, around 2100, the excess carbon dioxide that would have reached the atmosphere would have caused the 0.8 degree increase in the earth's temperature. But in addition, ODS are also greenhouse gases, that is, they alone would have triggered 1.7 degrees more ”. The scientist explains that, if we add these two figures, the study concludes that the Montreal protocol has prevented an additional 2.5 degrees of global warming. This protocol is the only UN text that has been ratified by all the countries of the world and, thanks to it and its subsequent amendments, the ozone layer is in the process of recovery.

To arrive at this estimate, the scientists connected five different computer models to create this alternate world where ODS had not been banned in 1987 and, on the contrary, would have grown at a rate of 3% each year. Chemicals that deplete the ozone layer, such as chlorofluorocarbons, were on the rise in the 1980s, and were used in aerosols, refrigeration (refrigerators, air conditioners), solvents, foams and even food: some soft drinks were made with non-toxic gases and the resulting bubbles were ODS. Without the Montreal Protocol, scientists have calculated that the ozone layer would have collapsed by the middle of our century, with dire consequences for human health. One of the countries that would have suffered the most is New Zealand,According to its Ministry of Health, it has the highest rate of skin cancer in the world (82,000 new cases each year). The study published in

has the contribution of meteorologist Olaf Morgenstern of NIWA, the Institute for Oceanic and Atmospheric Research in New Zealand. "Thanks to the Montreal protocol, the level of ODS in the stratosphere began to decline in 1997," he says. Although there have been some illegal emissions in China, the ozone layer continues to recover and, according to Morgenstern, the scientific community "expects it to be fully restored around the year 2060."

It is the first time that the effect that the increase in UV rays would have on the biosphere has been investigated on a global scale. The analysis published in

concludes that the destruction of the ozone layer would have decimated food production, as the radiation would have damaged crops. Furthermore, if vegetation loses the capacity to absorb carbon dioxide produced by human activity, scientists estimate that, without the Montreal Protocol, by the end of our century the atmosphere would have accumulated between 40% and 50% more carbon dioxide. carbon, or an extra 580,000 million of CO2. The extra warming that the planet would have suffered would make it impossible to meet the objective of the Paris agreement of limiting the increase in the earth's temperature to 1.5 degrees compared to pre-industrial levels.

The meteorologist Olaf Morgenstern is aware of what this would mean in the fight against climate change: “This is a very relevant figure.

The latest report from the IPCC [Intergovernmental Group of Experts on Climate Change] that was published in early August, warns of the difference that half a degree of temperature can represent for the planet.

If we add to this temperature the extra 0.8 degrees that the carbon not absorbed by the biosphere would have produced, this means that it would be impossible to limit global warming to 1.5 degrees, as required by the Paris Agreement ”.

Scientists estimate that, without the Montreal protocol, by the end of our century the atmosphere would have accumulated between 40% or 50% more carbon dioxide, or 580,000 million extra CO2

The Montreal Protocol was not born as a treaty against climate change, but according to a study published in 2019 by the Institute of Physics in the United Kingdom, it has been eight times more effective than other agreements specifically designed to reduce greenhouse gas emissions. greenhouse, like the 1997 Kyoto Protocol. According to Paul Young, governments can learn many lessons from the Montreal Protocol: “It is true that the ozone layer is a different problem than climate change. When it comes to ozone, we are talking about a small group of chemicals produced by a small group of companies. Although at that time there were no substitutes, the same companies were able to produce them. Instead, when we talk about CO2, it is the foundation of our entire economy and cannot be replaced.It is a much more difficult conflict to resolve ”. At the same time, the scientist reflects, we can draw a positive conclusion from the Montreal protocol: “The scientific community discovered that there was a problem, and the world agreed to deal with that problem as urgently as possible. It is a victorious example of international cooperation based on scientific knowledge ”.

The Montreal protocol would not have been possible without the contribution of two scientists who in 1974 published a study in the journal

on how ODS were destroying the ozone layer, the Mexican Mario Molina, and the American Frank Sherwood Rowland. At that time, every household in the United States had an average of 15 aerosols containing ODS. Although the chemical industry denounced the authors of the study for years, science ended up overcoming economic interests. In 1995 the Swedish Academy of Sciences awarded the two scientists the Nobel Prize in Chemistry, together with the Dutch Paul Crutzen, for their legacy in the fight to save the ozone layer.

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