Ozone Hole update

The antarctic ozone hole is a loss of stratospheric ozone in springtime over Antarctica that peaks in September each year. The hole first opened up in 1979, and has been proven to be the result of human emissions of large quantities of chlorofluorocarbons (CFCs) and other ozone-depleting substances into the atmosphere. The 2008 hole was the fifth largest on record, according to NASA. On September 12, 2008, the hole reached it maximum size of 27 million square kilometers, which was 12% larger than the 24 million square kilometers of the 2007 hole. The 2008 hole was larger than North America, which is 25 million square kilometers. Record ozone holes were recorded in both 2000 and 2006, when the size of the hole reached 29 million square kilometers. The 2008 hole was bigger than the 2007 hole due to the fact that the jet stream was quite stable over Antarctica this September, which allowed very cold air in the so-called "polar vortex" over Antarctica to remain isolated from the warmer regions farther to the north. As a result, when sunlight began shining on the Polar Stratospheric Clouds (PSCs) in the Antarctic during their spring (September), the resultant chemical reactions were able to destroy more ozone than in 2007.


Figure 1. Antarctic ozone hole size over the past few years. Image credit:NOAA's Climate Prediction Center.

Thanks for an international agreement called the Montreal Protocol in 1987, emissions of ozone-depleting gases have been sharply curtailed. NASA estimates that levels of ozone-depleting substances in the stratosphere peaked in 2000, and had fallen by 3.8% by 2008. The ozone hole is expected to disappear by 2050. The wunderground Ozone Hole page has more information.

--Jeff Masters, filling in for Ricky Rood this week.