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Ozone hole modest despite optimum conditions for depletion: Scientists

IANS  |  Washington 

Although colder-than-average temperatures in the created ideal conditions for destroying in 2018, declining levels of the depleting prevented the hole from being as large as it would have been 20 years ago, scientists from the NASA and (NOAA) have revealed.

The findings showed that the hole that forms in the upper over each September was slightly above the average size in 2018.

"This year's colder temperatures would have given us a much larger hole if chlorine was still at levels we saw back in the year 2000," said Paul A. Newman, for Earth Sciences at NASA's in Greenbelt,

According to NASA, the annual ozone hole reached an average area coverage of 22.9 square km in 2018.

NOAA scientists said colder temperatures in 2018 allowed for near-complete elimination of ozone in a deep, 5km layer over the South Pole. This layer is where the of ozone occurs on polar stratospheric clouds.

"Even with this year's optimum conditions, ozone loss was less severe in the upper altitude layers, which is what we would expect given the declining chlorine concentrations we're seeing in the stratosphere," added NOAA

Nations of the world began phasing out the use of ozone-depleting substances in 1987 under an international treaty known as the Montreal Protocol.

The 2018 ozone hole was strongly influenced by a stable and cold vortex -- the stratospheric low pressure system that flows clockwise in the above

In 2016 and 2017, warmer temperatures in September limited the formation of polar stratospheric clouds and slowed the ozone hole's growth. In 2017, the ozone hole reached a size of 19.7 square km before starting to recover.

In 2016, the hole grew to 20.7 square km.

However, the current ozone hole area is still large compared to the 1980s, when the depletion of the ozone layer above was first detected. Atmospheric levels of man-made ozone-depleting substances increased up to the year 2000.

Since then, they have slowly declined but remain high enough to produce significant ozone loss.

--IANS

rt/mag/sed

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)

First Published: Sat, November 03 2018. 13:42 IST
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