Scientists from NASA, the National Oceanic and Atmospheric Administration and the National Center for Atmospheric Research in Boulder, Colo., have developed a new tool, a math-based computer model, to predict more accurately when the ozone hole will recover.

The Antarctic ozone hole is a massive loss of ozone in the stratospheric layer of the atmosphere that occurs each spring in the Southern Hemisphere.

The ozone hole is caused by chlorine and bromine gases in the stratosphere that destroy ozone. These gases come from human-produced chemicals such as chlorofluorocarbons, also known as CFCs.

The ozone layer blocks 90 percent to 99 percent of the Sun's ultraviolet radiation from making contact with Earth. That harmful radiation can cause skin cancer, genetic and eye damage, and can harm marine life.

The new computer model combines estimates of future Antarctic chlorine and bromine levels with current amounts, as observed by NASA satellite observations, NOAA ground-level observations, NCAR airplane-based observations.

The model calculates future levels based on the time it takes for the transport of emissions into the Antarctic stratosphere, and on assessments of future weather patterns over Antarctica.

The model has accurately reproduced the ozone-hole area in the Antarctic stratosphere over the past 27 years. Based on those calculations, researchers think the ozone hole will recover in 2068 - not in 2050 as previously predicted.

"The Antarctic ozone hole is the poster child of ozone loss in our atmosphere," said lead researcher Paul Newman, of NASA's Goddard Space Flight Center.

"Over areas that are farther from the poles like Africa or the United States, the levels of ozone are only 3 percent to 6 percent below natural levels," Newman added.

He said over Antarctica, ozone levels are 70 percent lower in the spring. "This new method allows us to more accurately estimate ozone-depleting gases over Antarctica, and how they will decrease over time, reducing the ozone-hole area."

The Montreal Protocol and other international agreements have banned the production of most chemicals that destroy ozone, but the research shows the ozone hole has not started to shrink much as a result.

The scientists predict the ozone hole will not start shrinking a lot until 2018, although by that year, the recovery will make better time.

Related Links
Ozone data at NASA