The ozone layer begins to recover

Hole in Antarctica has shrunk 4 million square kilometers since its peak in 2000

It has been three decades of uncertainty since almost all countries in the world signed the Montreal Protocol, which prohibited the use of gases that destroy atmospheric ozone, and last October there was a fright when the hole in the ozone layer over Antarctica returned to grow. But things started to come together. Evidences have been found that in these days ozone layer is recovering.. Since 2000, when it reached its historic maximum (25 million square kilometers), the hole on the southern continent has been reduced by four million square kilometers, almost half of Brazil.

MORE INFORMATION

End of deforestation will not save the Amazon rainforest
Sea level rise brings several Pacific islands
The biologist who unlocks the latrines of the Olympic River
The researchers also show evidence that the main cause of recovery was the Montreal protocol, that is, the ban on chlorinated organic compounds (chlorofluorocarbons, CFCs) that were used in dry cleaning, refrigeration and sprays. The substitution of these compounds for others equally effective, but harmless to the atmosphere, was, therefore, of major importance.

There are also natural phenomena that damage ozone, such as temperature in the upper layers of the atmosphere and, above all, volcanic eruptions. This has complicated the measurements so far. In fact, the increase in the ozone hole that was recorded last October was due, scientists now think, to the eruption of the Calbuco volcano in southern Chile. Volcanoes do not emit CFCs, but a large number of small particles that rise into the atmosphere and favor reactions that destroy ozone.

Susan Solomon, a geologist at MIT (Massachusetts Institute of Technology) who pioneered research on ozone depletion for 30 years, presents the results in Science with colleagues at the National Center for Atmospheric Research in Boulder (Colorado) ), and the University of Leeds, UK. The work combines observations by balloons and satellites with advanced mathematical models.

Solomon is elated. "Now we can believe that the things we are doing have put the planet on the path to healing," he says. “It says a lot about us, doesn't it? Aren't we amazing, humans, that we created a situation after we collectively decided, as a world, that we were going to eliminate these molecules? We eliminated them, and now we are seeing that the planet responds. ”

Ozone loss has direct effects on health, because this gas is, in the upper layers of the atmosphere, the most important natural protection against ultraviolet radiation from sunlight, which causes skin cancer, cataracts and damage to the immune system. The United Nations estimates that the Montreal Protocol will prevent two million cases of skin cancer since its entry into force until 2030. Ozone loss affects all latitudes, but is more severe at the poles, and especially in Antarctica, which is where the magnitude of the hole is measured.

The hole in the ozone layer was discovered in the 1950s, and its gravity was confirmed in the 1980s. Measurements have been made since then in the months of October, when spring creates conditions conducive to the destruction of ozone in the upper layers. Solomon and his colleagues now show the benefits of measuring it in September, shortly after Antarctica began to emerge from the dark southern winter. Light is needed for reactions that damage ozone.