Ozone layer berhole is shrinking: NASA

In a positive development on the environment front, satellite measurements reveal that the hole in the earth's protective ozone layer is shrinking and has shriveled to its smallest peak since 1988, NASA scientists said.

The hole had become the largest this year at 7.6 million square miles wide, about two and a half times the size of the US, in September, but was still 1.3 million square miles smaller than last year, scientists said, and has shrunk more since September.

The shrinkage is due to the warmer-than-usual weather conditions in the stratosphere since 2016, as the warmer air helped to keep away chemicals such as chlorine and bromine that eat away at the ozone layer, scientists said. However the reduction could be traced to global efforts since the mid-1980s to ban the emission of ozone-depleting chemicals.

''Weather conditions over Antarctica were a bit weaker and led to warmer temperatures, which slowed down ozone loss,'' said Paul Newman, chief Earth scientist at NASA's Goddard Space Flight Center in Maryland. ''It's like hurricanes. Some years, there are fewer hurricanes that come onshore ... this is a year in which the weather conditions led to better ozone (formation).''

Balloon-based measurements by the National Oceanic and Atmospheric Administration (NOAA) also showed the least amount of ozone depletion above the continent during the peak of the ozone depletion cycle since 1988. The NOAA in collaboration with NASA also monitors the growth and recovery of the ozone hole every year.

''The Antarctic ozone hole was exceptionally weak this year,'' said Newman, NASA reported. ''This is what we would expect to see given the weather conditions in the Antarctic stratosphere.''

The international community signed the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987 and started regulation of ozone-depleting compounds. According to experts, the ozone hole over Antarctica is expected to gradually shrink as chlorofluorocarbons, chlorine-containing synthetic compounds once frequently used as refrigerants continue to decline. Scientists expect the Antarctic ozone hole to recover to the 1980 levels around 2070.