NASA has confirmed that the hole in the Earth’s ozone layer, which first appeared above Antarctica in the 1980’s, is shrinking thanks to a ban on damaging chemicals. In 1989 the world came together in the Montreal Protocol, which banned ozone-depleting chemicals called chloro-flurocarbons (CFC’s). At the time these CFC’s were widely used in aerosols, refrigerators and air conditioning. It was thought that they were the cause of the shrinking ozone layer because the chlorine gas that they give off damages ozone. Last year satellite images seemed to show that the ozone hole had begun to close up, but it was not clear that this was due to the ban on CFC’s.
The latest research has found that the amount of chlorine in the planet’s atmosphere has significantly declined as a direct result of the CFC ban. According to Dr Susan Strahan of Nasa’s Goddard Space Flight Centre (US): “This is evidence that the Montreal Protocol is working – the chlorine is decreasing in the Antarctic stratosphere, and the ozone destruction is decreasing along with it.” What exactly is the Ozone Layer? The Earth’s stratosphere stretches roughly 10 to 40 kilometres above the surface. It contains this layer of ozone which acts like a sunscreen – shielding the planet from potentially harmful ultraviolet radiation that can cause skin cancer and also damage plants.
CFC’s are broken down by the sun’s ultraviolet radiation when they rise into the stratosphere, releasing chlorine atoms that destroy ozone molecules. Since 2005 NASA has been monitoring the hole in the ozone layer with its Aura satellite. This new study used Aura readings of the chemical composition of the hole to prove that there has been a 20% drop in chlorine since the Montreal protocol came into effect, and a corresponding 20% decrease in the size of the hole. Dr Strahan cautions that, “CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time. As far as the ozone hole being completely gone, we are looking at sometime between 2060 and 2080.”