Thursday, 13 May 2010

Statistics

▪ Lowest ozone in 1994
• Arctic ozone depletion is highly variable and difficult to predict, but a future Arctic polar ozone hole similar to that of the Antarctic appears unlikely.
• Ozone concentrations in the lower stratosphere over Antarctica will increase by 5%–10% by 2020 and return to pre-1980 levels by about 2060–2075, 10–25 years later than predicted in earlier assessments.
• Detectable recovery by 2024
• Antarctic hole recover in 2068


Graph Showing Ozone Depleting Substances — and a larger predicted future usage in developing countries



Changes in Ozone-Depleting Compounds
▪ In the troposphere observations show that the total abundance of ozone-depleting compounds continues to decline slowly from the peak that occurred in 1992-1994.
▪ Observations in the stratosphere indicate that the total chlorine abundance , bromine abundances and HCFCs

Changes in the Ozone Layer over the Poles and Globally
▪ Springtime Antarctic ozone depletion due to halogens has been large (40-50%; exceptionally 70%) throughout the last decade.
▪ In some recent cold Arctic winters during the last decade, maximum total column ozone losses due to halogens have reached 30%, but in warmer winters Arctic ozone loss is small.
▪ Ozone remains depleted in the midlatitudes of both hemispheres. The global-average total column ozone amount for the period 1997-2001 was approximately 3% below the pre-1980 average values.
▪ Models capture the observed long-term ozone changes in northern and southern midlatitudes.

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