Sunday, July 2, 2006

Stratospheric Ozone -- hole expected to close by mid-century....well, 2068

Science Daily reports on further delays in closing the hole:

The Antarctic ozone hole's recovery is running late. According to a new NASA study, the full return of the protective ozone over the South Pole will take nearly 20 years longer than scientists previously expected. 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 better predict when the ozone hole will recover....For the first time, a model combines estimates of future Antarctic chlorine and bromine levels based on current amounts as captured from NASA satellite observations, NOAA ground-level observations, NCAR airplane-based observations, with likely future emissions, the time it takes for the transport of those emissions into the Antarctic stratosphere, and assessments of future weather patterns over Antarctica.  The model accurately reproduces the ozone hole area in the Antarctic stratosphere over the past 27 years. Using the model, the researchers predict that the ozone hole will recover in 2068, not in 2050 as currently believed.  "The Antarctic ozone hole is the poster child of ozone loss in our atmosphere," said author Paul Newman, a research scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. And lead author of the study. "Over areas that are farther from the poles like Africa or the U.S., the levels of ozone are only three to six percent below natural levels. 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."  International agreements like the Montreal Protocol have banned the production of most chemicals that destroy ozone. But the researchers show that the ozone hole has not started to shrink a lot as a result. The scientists predict the ozone hole will not start shrinking a lot until 2018. By that year, the ozone hole's recovery will make better time.

original 8/23/05 post: The World Meteorological Organzation reports that even though the winter ozone hole above Antarctica is larger than last year, it is still smaller than the largest hole recorded in 2003.  With ozone-depleting substances banned and concentrations of those substances leveling off, the hole is expected to grow bigger for a few more years and then gradually disappear by mid-century.

As reported in Reuters: OZONE

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Comments

The Antarctic ozone hole develops each year between late August and early October. Regions with higher levels of ozone are shown in red. Ozone depletion means that ozone loss is exceeding ozone creation. Putting additional ozone-destroying compounds such as CFCs into the atmosphere is like increasing the size of the holes in our "bucket" of ozone. The larger holes cause ozone to leak out at a faster rate than ozone is being created. Consequently, the level of ozone protecting us from ultraviolet radiation decreases.

Posted by: George | Jul 25, 2008 2:06:08 AM

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