The fight for the preservation of the ozone layer continues, and reducing one of its largest holes has been one of the greatest challenges. But how are you currently? How has it been recovered? From Eltiempo.es, it shelled in seven questions the basic aspects to understand its importance.
The ozone layer is an atmospheric strip located in the stratosphere, about 25 kilometers high, and is denser at high latitudes, reaching its highest density near the poles.
1. How is it formed and destroyed?
Ozone forms naturally in the stratosphere by the combination of oxygen atoms and molecules, and in the presence of other molecules, such as nitrogen, abundant in the atmosphere.
Just as it is created, it can be destroyed: By absorbing ultraviolet radiation, it decomposes back into molecular oxygen and atomic oxygen. Ozone can also break down when it collides with other elements, such as nitrogen, hydrogen or chlorine atoms. Therefore, the ozone concentration in the stratosphere can vary naturally.
2. What is the ozone hole?
This decrease in layer thickness was more intense over Antarctica, in the southern hemisphere, and occurred as ozone destruction increased in this region.
For several springs ozone concentrations in Antarctica were exceptionally low and the hole in the ozone layer formed caused by anthropogenic action.
3. Why is it produced?
First you have to understand where it happens. The stratosphere over Antarctica has one of the highest concentrations of ozone of the world. And, most of it is formed over the tropics and carried to Antarctica by stratospheric winds.
During the long, dark Antarctic winter, which runs from June to September, the temperatures inside the vortex they can drop as low as -85 ° C. Forming polar stratospheric clouds, which contain reagents that destroy ozone.
With the arrival of spring in the southern hemisphere, sunlight returns to these regions facilitating chemical interactions that break down ozone.
4. Why was this process accelerated?
Although it is a natural reaction, this is when emissions come into play of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), caused by humans.
These long-lived compounds are some of the main ozone destroyers, but before they were banned they had multiple uses. They were used for refrigeration and were present in deodorants or hairspray.
5. How was a solution to the problem found?
In 1974, F. Sherwood Rowland and Mario J. Molina, warned that some compounds could be the causing ozone destruction. In 1985 the great hole was discovered and already in 1987 the Montreal Protocol of 1987 was created with a calendar for the reduction of emissions and the use of these compounds.
The hole in the ozone layer reached its maximum extent in September 2000. Currently, various studies indicate that ozone levels will return to pre-1980 values by 2050. The only exception is Antarctica, where ozone concentrations are likely to remain low until about 2070.
6. Is it due to climate change?
No, it is not. Although these compounds also favor global warming, their impact on the ozone hole is not associated with climate change. Once the use of these compounds was banned, the ozone hole began to slowly recover.
7. Is there an ozone hole in the Arctic?
While the ozone hole over Antarctica is observed annually, over the Arctic you rarely have a similar phenomenon. This is because the polar vortex in the northern hemisphere is not as intense and temperatures are typically above -78ºC. This prevents polar stratospheric clouds from forming and less or no ozone destruction.
That is why it was especially striking the strange ozone hole that appeared over the Arctic last March 2020. The very low temperatures of winter allowed the formation of polar stratospheric clouds and the subsequent loss of ozone, of up to 30%.