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Ozone hole grew this year, but still shrinking in general

The Antarctic ozone hole last week peaked at a moderately large size for the third straight year — bigger than the size of North America — but experts say it’s still generally shrinking despite recent blips because of high-altitude cold weather.

The ozone hole hit its peak size of more than 10 million square miles on Oct. 5, the largest it has been since 2015, according to NASA. Scientists say because of cooler-than-normal temperatures over the southern polar regions at 7 to 12 miles high where the ozone hole is, conditions are ripe for ozonemunching chlorine chemicals.

“The overall trend is improvement. It’s a little worse this year because it was a little colder this year,” said NASA Goddard Space Flight Center chief Earth scientist Paul Newman, who tracks ozone depletion. “All the data says that ozone is on the mend.”

Chlorine and bromine chemicals high in the atmosphere eat at Earth’s protective ozone layer. Cold weather creates clouds that release the chemicals, Newman said. The more cold, the more clouds, the bigger the ozone hole.

Climate change science says that heat-trapping carbon from the burning of coal, oil and natural gas makes Earth’s surface warmer, but the upper stratosphere, above the heat-trapping, gets cooler, Newman said. However, the ozone hole is slightly lower than the region thought to be cooled by climate change, he said. Other scientists and research do connect cooling in the area to climate change.

“The fact that the stratosphere is showing signs of cooling due to climate change is a concern,” said University of Leeds atmospheric scientist Martyn Chipperfield. The worry is that climate change and efforts to reduce the ozone hole get intertwined.

Decades ago atmospheric chemists noticed that chlorine and bromine were increasing in the atmosphere. In 1987, the world agreed to a landmark treaty, the Montreal Protocol, that banned ozone-munching chemicals, often hailed as an environmental success story.

—The Associated Press

NASA image, the blue shows the hole in Earth’s protective ozone layer over Antarctica on Oct. 5. It generally has been shrinking but grew to a moderately large size this year because of weather conditions.







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