Scientists from NASA’s Goddard Space Flight Center established that the ozone layer has not begun to recover despite the ban on the use of ozone-depleting chemicals. With the help of satellite data, the team was able to monitor changes in size of the second largest ozone hole located over Antarctica, and found that meteorological conditions have created the false belief that the ozone hole has stopped growing.
CFC, or chlorofluorocarbon, has been known for its ability to break down ozone in the stratosphere. As soon as this was established, the world banned its use with the Montreal Protocol agreement, and since then scientists have been monitoring closely the changes in chlorine concentrations in the stratosphere, where the ozone layer is found. Until now, studies have shown that indeed the ban has worked, and the already formed ozone holes have stopped enlarging, but unfortunately two new studies proved that this is not true.
Susan Strahan and her colleague Natalya Kramarova from NASA Goddard presented the results from a study they conducted at the yearly meeting of the American Geophysical Union, held in San Francisco. They showed a series of maps indicating changes in amount of ozone with altitude, produced with data acquired by the NASA-NOAA Suomi National Polar-orbiting Partnership satellite. The results indicate that winds carry ozone across the stratosphere, creating the false impression that the hole is not expanding. The confusion, according to the scientists, have occurred because previous studies base their findings on total ozone values, which do not explain the processes fully.
In the past, Strahan has also monitored another two major ozone holes, aiming to identify reasons to why they have formed. Relying on satellite data, this time from the NASA Aura satellite’s Microwave Limb Sounder, the researcher was able to monitor concentrations of ozone-depleting substances and found that although chlorine was present in different amounts, the holes were still of the same size. In a study submitted to the journal of Geophysical Research Letters, Strahan and team again demonstrate that different amounts of ozone are transported by winds each year, causing the greater ozone destruction when more ozone is present and vice versa.
Srahan concludes that although the ban on CFCs has been imposed more than 20 years ago, the drop in concentrations of the substances is way too small to have triggered ozone layer recovery.
Iamge (c) NASA/NOAA