The ozone hole over Antarctica grew to the size of North America in September, the fifth-largest since satellite records began in 1979, the Natiocnal Oceanic and atmospheric Administration said.
The ozone hole is primarily caused by manmade compounds known as chlorofluorocarbons, NOAA said today. Colder-than-average temperatures in the stratosphere may also have allowed a larger ozone hole to develop this year than in 2007, the agency said.
“Weather is the most important factor in the fluctuation of the size of the ozone hole from year-to-year,” said Bryan Johnson, a scientist at NOAA’s Earth System Research Laboratory in Boulder, Colorado. “How cold the stratosphere is and what the winds do determine how powerfully the chemicals can perform their dirty work.”
Record-breaking ozone loss in 2006 occurred as ozone thickness plunged and the hole stretched over 11.4 million square miles at its peak. Last year’s ozone hole was average in size and depth.
The ozone layer acts like a giant umbrella, blocking some of the sun’s ultraviolet rays. NASA satellites measured the maximum area of this year’s ozone hole at 10.5 million square miles and four miles deep on Sept. 12.
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