NASA and NOAA scientists reported this week that they have observed the smallest ozone hole since 1982 — the year that it was first discovered.
While this is excellent news, the scientists do point out that the reduced ozone depletion this year was caused by abnormal weather conditions.
The ozone hole is continuously fluctuating. It usually reaches its peak size in or around October.
This year, that peak was reached on Sept. 8 when the hole was measured at 6.3 million square miles, a NASA blog post says. It then shrank to less than 3.9 million square miles (10 million square kilometers) for the rest of September and October, according to NASA and NOAA satellite measurements.
In years with normal weather conditions, the ozone hole usually grows to a maximum area of about 8 million square miles at around the same period.
"It’s great news for ozone in the Southern Hemisphere,” said Paul Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center.
“But it’s important to recognize that what we’re seeing this year is due to warmer stratospheric temperatures. It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery.”
A rare occurrence
In the last 40 years, there have been three recorded incidents where warm temperatures have limited ozone depletion, said Susan Strahan, an atmospheric scientist at NASA Goddard, in the NASA post.
Similar weather patterns occurred in the Antarctic stratosphere in September 1988 and 2002, and these also produced smaller ozone holes, she explained.
“It’s a rare event that we’re still trying to understand,” said Strahan. “If the warming hadn’t happened, we’d likely be looking at a much more typical ozone hole.”
While NASA scientists are still trying to understand the exact effects of warm temperatures on ozone depletion, they say there is no known link between these unique patterns and climate change.