Antarctic ozone hole expands to near-record size
According to atmospheric scientist Professor David Karoly from the University of Melbourne, its size fluctuates greatly when it emerges each spring.
"Each springtime over the last now nearly 35 years, there's been a depletion of stratospheric ozone over Antarctica primarily due to two really important factors," he said.
"It's the increase in ozone-depleting chemicals in the atmosphere and a very special cold conditions that occur in winter and spring over Antarctica which provide a special, if you like, catalytic ozone destruction vessel that allows the ozone to be rapidly deployed by the higher concentrations of chlorofluorocarbons — ozone-depleting chemicals that have occurred in the stratosphere due to human activity."
The UN's weather and climate agency said this year's seasonal ozone hole peaked on October 2, covering an area over Antarctica of 28.2 million square kilometres — close to four times the size of Australia or the size of Russia and Canada combined.
The Antarctic ozone hole widened to one of its largest sizes on record earlier this month, the U.N.'s World Meteorological Organization (WMO) announced Thursday.Scientists warn of higher UV levels as Antarctic ozone hole expands - The Globe and Mail
The hole's large size was due to unusually cold temperatures in the stratosphere, the level of the atmosphere where the ozone hole and ozone layer are located, the agency said.
"This shows us that the ozone hole problem is still with us and we need to remain vigilant. But there is no reason for undue alarm," Geir Braathen, a senior scientist in WMO's Atmospheric and Environment Research Division, said in a statement.
Ozone depletion - Wikipedia, the free encyclopediaA widely hailed international accord in 1987 to phase out use of ozone-depleting chemicals has underpinned hopes for recovery of stratospheric ozone worldwide by 2070. WMO and NASA say the hole had been levelling off and even shrinking a bit, and hope this year’s one-off expansion of the ozone hole will have little to no impact on the overall trend toward that goal.“There is no need for undue alarm because we are on a course to recovery, but we have not observed it yet,” said WMO scientist Geir Braathen, who wrote the bulletin. “CFCs (chlorofluorocarbons), they have a long life in the atmosphere ... many, many decades. It takes a long time for these molecules to get out of the atmosphere.”“We are suffering now from the sins of the past,” he added.
Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% in the total volume of ozone in Earth's stratosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone around Earth's polar regions. The latter phenomenon is referred to as the ozone hole. In addition to these well-known stratospheric phenomena, there are also springtime polar tropospheric ozone depletion events.