Past studies have used statistical analyses of changes in the ozone
hole's size to argue that ozone depletion is decreasing.
The minimum value of total ozone in the ozone
hole was the second highest level in two decades.
If bromine concentrations peaked in the lower atmosphere in 1998, then they should soon be declining up in the ozone
layer, if they aren't already.
For two decades, an ominous hole in the ozone
layer has ballooned over Antarctica, alarming scientists.
Even in the ozone
layer, Earth's highest natural ozone concentration, only about 3 molecules of ozone occur for every 10 million molecules of air.
Scientists estimate that every one percent decrease in the ozone
layer increases ultraviolet light intensity at the earth's surface by two percent.
This also means that the seasonal holes in the ozone
layer over the Arctic and Antarctic would represent nothing more than normal fluctuations in the ozone
The ring design of the annulus test piece (inside diameter exactly 1/2 the outside diameter) allows a continuous range of strain observations (0 to 100%) when the test piece is mounted in the ozone
test chamber apparatus.
Ten years later, when another scientist detected a "hole" in the ozone
layer over Antarctica, people began to heed Molina's warnings.
Ozone holes - regional thinnings in the ozone
layer - have developed over the Antarctic continent each September since the late 1970s.
That weakening in the ozone
layer would let some 6 to 12 percent more ultraviolet light reach Earth's surface, raising the risk of skin cancer, cataracts and damage to animals and plants.
Most chlorine in the ozone
layer comes from chlorofluorocarbons and other forms of pollution.
The hole is a reduction in the ozone
layer that normally shields Earth's surface from much of the sun's ultraviolet rays.
Schoeberl, an atmospheric scientist with NASA, also notes that chlorine monoxide (ClO)--a principal chemical active in the ozone
destruction--was not always present at altitudes that would account for the low ozone levels.