For the first time, scientists have shown through direct satellite observations of the ozone hole that levels of ozone-destroying chlorine are declining, resulting in less ozone depletion.
We all know about the international ban on chlorine-containing manmade chemicals called chlorofluorocarbons(CFCs). Measurements show that the decline in chlorine has resulted in about 20 percent less ozone depletion during the Antarctic winter than there was in 2005. It was in 2005 measurements of chlorine and ozone were taken for the first time during the Antarctic winter by NASA’s Aura satellite.
We all have studied about CFCs in our school, right? Yes, CFCs are long-lived chemical compounds that eventually rise into the stratosphere, where they are broken apart by the Sun’s ultraviolet radiation, releasing chlorine atoms that go on to destroy ozone molecules. We can never ask why we need to bother about this ozone molecules as the ozone protects life on the planet by absorbing potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and damage plant life. So Ozone is like our planet’s protective shield. We can’t let anything happen to it.
Have you ever heard of the Montreal Protocol? Well, two years after the discovery of the Antarctic ozone hole in 1985, nations of the world signed the Montreal Protocol on Substances that Deplete the Ozone Layer, which regulated ozone-depleting compounds. Later amendments to the Montreal Protocol completely phased out production of CFCs.
Past years many studies were done to check if changes were taking place in the ozone hole’s size. This study used measurements of the chemical composition inside the ozone hole to confirm that not only is ozone depletion decreasing, but that the decrease is caused by the decline in CFCs. The study was published on Jan 4 in the journal Geophysical Research Letters.
Let’s see how the scientists carried out these studies? To determine how ozone and other chemicals have changed year to year, scientists used data from the Microwave Limb Sounder (MLS) aboard the Aura satellite, which has been making measurements continuously around the globe since mid-2004. The change in ozone levels above Antarctica from the beginning to the end of southern winter — early July to mid-September — was computed daily from MLS measurements every year from 2005 to 2016.
Results were amazing as they found that ozone loss is decreasing, but they needed to know whether a decrease in CFCs was responsible for this or not. Now let’s understand how they came to a conclusion.
Actually, when ozone destruction was ongoing, chlorine was found in many molecular forms, most of which were not measured. But after chlorine has destroyed nearly all the available ozone, it reacts instead with methane to form hydrochloric acid, a gas measured by MLS. By around mid-October, all the chlorine compounds are conveniently converted into one gas, so by measuring hydrochloric acid they got a good measurement of the total chlorine,
You might have heard of Nitrous oxide which is also a long-lived gas that behaves just like CFCs in much of the stratosphere. The CFCs are declining at the surface but nitrous oxide is not. If CFCs in the stratosphere are decreasing, then over time, less chlorine should be measured for a given value of nitrous oxide. By comparing MLS measurements of hydrochloric acid and nitrous oxide each year, they determined that the total chlorine levels were declining on average by about 0.8 percent annually.
The scientists stated that the Antarctic ozone hole would continue to recover gradually as CFCs leave the atmosphere, but the complete recovery will take decades. CFCs have lifetimes from 50 to 100 years, so they linger in the atmosphere for a very long time. They think that by 2060 or 2080 the ozone may recover but even then there might still be a small hole.
See how our reckless activities are causing wounds on our planet which can never be healed. Let’s try to live better on the planet and leave a better place for the coming generations to live on and pass on.
