NASA finds largest-ever ozone hole

GREENBELT, Maryland (CNN) -- Scientists at NASA's Goddard Space Flight Center said they have located the largest ozone hole ever recorded, an area approximately three times the size of the United States.

In a report released Wednesday, NASA said satellites observed an 11.5 million square-mile hole --actually a severe thinning of Earth's protective ozone layer-- last month over Antarctica.

Scientists blamed a combination of the usual suspects -- chloroflourocarbons (CFCs) and other ozone-eating chemicals -- and an upper-level wind called the polar vortex, which swirls around Antarctica. This year, the vortex's swirl is bigger than usual, "and so the fact that it's a little bit bigger creates a bigger ozone hole," said NASA's Paul Newman.

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NASA said atmospheric levels of CFCs have leveled off in the wake of the 1987 Montreal Protocol, which aims to phase out production of ozone-destroying chemicals. But the chemicals can stay in the atmosphere for decades, so it will be a long time before a chemical crackdown on earth will translate to changes in the stratosphere.

The depletion of the ozone layer allows more of the sun's harmful ultraviolet rays to reach Earth. Researchers say that leads to higher rates of skin cancer. They are also worried about the ocean around Antarctica because plankton, the base of the food chain there, may be vulnerable to higher levels of ultraviolet radiation.

Scientists also are trying to determine whether there is a relationship between the formation of ozone holes and global warming, the theory that certain kinds of pollution create an atmospheric blanket that warms the Earth.

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Air Resources Laboratory
Montreal Protocol
Journal of Geophysical Research
ozone depletion and human health effects
EPA's page on ozone
NASA's Total Ozone Mapping Spectrometer
Air Resources Laboratory
Peering into the Ozone Hole