Few days back, scientists from the National Oceanic and Atmospheric Administration (NOAA) and NASA announced that the Antarctic ozone hole was much larger this year than in recent years; a near-record hole. At the beginning of October, the ozone hole expanded to its peak of 10.9 million square miles/28.2 million square kilometers, or an area roughly the size of North America. This is about 2 million square miles above the 21st century average.
But, UN scientists insist ozone is recovering despite huge hole. “There is no reason for undue alarm,” said meteorologist Geir Braathen. So, are you confused?
Actually, this is true. While the hole in the ozone layer overall is actually shrinking, the size of the hole can fluctuate widely from year to year. This year, unusually cold temperatures and weak atmospheric dynamics in the stratosphere are likely responsible for the larger hole. The World Meteorological Organization, the UN’s weather agency, blamed the larger than usual hole on “colder than usual high-altitude (stratospheric) meteorological conditions.”
Wait, so unusually COLD temperatures are responsible for the hole??
Yes, here’s how ozone works. O3, which is what ozone is molecularly (remember that oxygen is O2), is produced and attracted by a combination of heat and the suns radiation. So wherever there is more heat and solar radiation, that’s where you find more ozone. It typically lives in the Stratosphere, but you can get ozone at the surface as well on really hot days, that’s why you will sometimes hear of ozone advisories in some of the big cities across the globe during the heart of the summer.
Unfortunately, ozone is toxic to humans when breathed, so we need it to shield us from the sun, but we also don’t want to breathe it. There is always more heat and radiation near the equator, so the stratospheric ozone levels are huge around the equator and often very small in the North and South Pole regions. But with even colder than normal temperatures in the South Pole this winter (Northern Hemisphere summer) even more ozone was lost to the equator than normal leaving a bigger hole.
So, coming back to the question whether the ozone layer over Antarctica is expanding or shrinking? Well, here is what the researchers have to say…
Despite the hole’s expanded size, researchers say the ozone’s continued recovery is not in jeopardy. “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,” said Geir Braathen, a senior scientist with WMO’s Atmospheric and Environment Research Division.