In the 1970s, scientists sounded the alarm: the ozone layer was deteriorating. This protective barrier that filters ultraviolet (UV) rays from the sun is gradually disappearing over Antarctica. A few years later, in 1987, twenty-four countries and the European Economic Community took note of this alert and signed a historic agreement aimed at protecting this gaseous envelope. This treaty, called the Montreal Protocol, bans substances that destroy the ozone layer, such as chlorofluorocarbons (CFCs), used in the refrigeration industry. Forty years later, all the countries of the planet have ratified this agreement.
An international team of scientists has sought to find out what the state of our planet would have been if this historic event had not existed. This scenario, published on August 18 in the scientific journal Nature, depicts a vision of an Earth where CFCs are still relevant. “We wanted to know if the Montreal Protocol had been effective, says Paul Young, a climate scientist at Lancaster University and the study’s first author. The best way to do this is to model a world where this protocol never existed and compare it to a world where it exists. “
This parallel planet, scientists call it World Avoided, or the “avoided world”. Their work reveals that if ozone-depleting chemicals had not been controlled, their continued use would have contributed to a global temperature rise of 2.5 ° C by the turn of the century.
The impact of ultraviolet light on plants
According to the study, the ban on CFCs protected the climate in two ways. First of all by reducing the greenhouse effect of these gases, which would have contributed to an increase of 1.7 ° C. But also by protecting plants from ultraviolet radiation. “UV has a direct impact on the growth capacity of plants and on photosynthesis, explains Paul Young. High UV means less carbon is absorbed by plants. Less carbon in plants means more carbon in the atmosphere. “ This would have resulted in a temperature increase of 0.8 ° C.
“A number of studies have appeared on World Avoided and the collapse of the ozone layer, explains Sophie Godin-Beekmann, research director at CNRS and president of the International Commission on Ozone, which did not participate in the study. But this is the first time that a study has gone further and assessed the effects of increased UV radiation on plants. “
You have 53.44% of this article to read. The rest is for subscribers only.