Human actions have consequences. It takes years for humankind to acknowledge a certain problem and start working on a solution for it. When it was discovered in the 80s, the ozone depletion became one of the biggest environmental threats and one of the best-known symbols of the human capacity to cause damage to the environment unintentionally. The loss of this high layer of the atmosphere -stratospheric molecules consisting of three oxygen atoms – is related to the increase of skin cancer cases because it acts as a filter for harmful ultraviolet rays (UV).
Image source: Slideshare
The main cause of the advancement of this big hole over Antarctica was the chlorine present in these high layers of the atmosphere from molecules called chlorofluorocarbons (CFC). At the time, these were issued by the sprays, cooling systems and products for dry cleaning. For this reason, in 1987, almost all the countries of the world jointly signed a protocol in Montreal (Canada) to eliminate the use of CFCs for the sole purpose of recovering the ozone layer.
Image source: io9.com
Today, almost 30 years later, it is a global effort that has paid off. The ozone layer is recovering, and the gaping hole over Antarctica has shrunk more than 4 million square kilometers since 2000, according to the recently published research in the journal Science. Work has also been led by the prestigious researcher at the Massachusetts Institute of Technology (MIT), Susan Solomon, who discovered in 1986 the relationship between the presence of chlorine, the incidence of light and the low temperature of the atmosphere as key factors which initiate the disappearance of stratospheric ozone.
Susan Solomon. Image source: news.mit.edu
The combination of chlorine, sunshine, and low temperature creates the polar stratospheric clouds in the chemistry of chlorine that is produced, so it is lethal to the ozone layer. For that reason, the period of greatest destruction begins in August, when Antarctica begins to emerge from its dark austral winter and reaches its maximum size hole in October. Hence, measurements have always been taken during the month of October. However, Solomon and her colleagues, who include US and British researchers, thought that perhaps some years the conditions of September would be more favorable to measure the effects of chlorine on the ozone. Time has proved them right.
The authors have demonstrated, for the first time, chlorine levels descended as a result of the ban on CFCs and the rate at which the ozone hole increases in September has slowed down between 2000 and 2015. Compared to the moment of maximum ozone loss in 2000, the size of the hole shrank more than 4 million square kilometers in 2015, further reducing comparable to the size of India and Spain together. That year, despite the steady reduction of atmospheric chlorine, the ozone hole reached a new record of maximum size. What was happening then?
Solomon immediately returned to the data to try and understand what was happening until she realized that this new peak in reducing ozone was mainly due to the eruption of the Chilean volcano Calbuco, which had its last major eruption during April of 2015. It is true that volcanoes emit a large amount of chlorine into the atmosphere; these are small particles, increasing the presence of polar stratospheric clouds that create the ideal environment for active chlorine. That is why there is reason to think that, regardless of volcanic eruptions, reducing the presence of chlorine in the stratosphere shrinks the hole slowly.
There are still many years ahead of trying to fix the damage that our kind has caused to the planet, but the first positive results give us the hope and will to continue finding new solutions and ways to heal it, thinking of the future of humankind.