Oct. 19, 2006  -- The so-called "hole" in the earth's protective ozone layer is at a new record -- 10.6 million square miles of sky around the South Pole -- even though most nations agreed back in 1987 to phase out the chemicals that cause it.

The number was reported today by U.S. government scientists, who said protecting the ozone layer was still clearly the right thing to do, but that it's taking longer than originally expected for the ozone layer to heal. A 10.6 million mile gap in it is about the size of North America.

"It's going to be like this for the next decade," said Paul A. Newman, a senior research scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "And then it will start tipping over, and decreasing, and be gone around 2070."

That's a delay of 15-20 years. Early computer models had shown the ozone layer would be back to normal around 2050.

Ozone Layer Vital to Life

Ozone molecules, which form in the upper atmosphere and waft around approximately 12-20 miles above the Earth's surface, protect us from the harmful ultraviolet rays of the Sun.

If ozone is destroyed, scientists say there would be multiple effects -- increased rates of skin cancer and cataracts; and death of tiny plankton in the oceans, which form the base of the world's food chain in many cases.

Scientists gave the world a shock in the 1970s and 1980s. They realized that commonly-used chemicals -- the CFCs and halons used in everything from air conditioners to fire extinguishers to spray cans -- were escaping into the stratosphere. Through complex reactions, they were eating away at the amount of ozone there.

What was more, they found that in the early spring in the southern hemisphere -- September and October -- a giant ozone "hole" formed in the swirling air currents over Antarctica, and often spread over South America, Australia and New Zealand.

The response was a 1987 treaty called the Montreal Protocol, calling for the phase-out of CFCs and other chemicals. The treaty has been hailed as a model of international cooperation; to date, 189 countries have signed it.

New Measurements from Orbit

But new readings, provided by the Ozone Measuring Instrument aboard NASA's earth-observing Aura satellite, show what scientists suspected -- that even if CFCs are no longer made, molecules of the gases survive in the upper atmosphere for 40 to 100 years.

So the ozone hole has appeared again, bigger than ever.

"These numbers mean the ozone is virtually gone in this layer of the atmosphere," said David Hofmann, director of the Global Monitoring Division at the NOAA Earth System Research Laboratory, in a statement. "The depleted layer has an unusual vertical extent this year, so it appears that the 2006 ozone hole will go down as a record-setter."

Does that mean the Montreal treaty has been a failure? Hardly, say the scientists who have worked on the issue -- if nothing had been done, the ozone loss would be much greater.

But they say people need to recognize how complex the chemistry of the atmosphere is, and be patient.

"It's very clear what happened over Antarctica, and why it happened," said NASA's Newman. "There's absolutely no question at all about the causes of the ozone hole."