Slashdot Mirror
Antarctic Ozone Hole Leveling Off
twistedfuck writes: "An Irish Time article reports that the size of the hole in the antartican ozone layer is levelling off and should begin reducing in size. It seems like it should be welcome news but it is tempered by the fact that more UV radiation will reach the southern hemisphere this year because the hole will persist longer. Unfortunately I can not find any details regarding the NOAA report on their website." Update: 11/06 17:31 GMT by H :Thanks to Isaac Lewis, NOAA Sysadmin and Slashdot reader, for pointing out more information, as well as pointing out the ozonelayer site.
Sunlight naturally converts some oxygen to ozone in the upper atmosphere. Problem is that when CFCs and other chemicals are present, they eat up ozone far faster than it is typically produced.
Ozone is harder to produce and easier to break down when it is cold, which is one reason ozone is at its lowest levels over the poles in winter (also when there is a deficit of sunlight). The poles are also especially vulnerable because global wind patterns circle around them rather then refreshing the air. Even the most stubborn air pollutants will break down or become absorbed by the environment if we stop pumping them out and give the Earth time to get back to normal.
Which volcano in the Phillipines poured out CFCs? I'd be very interested in hearing about a volcano that poured out chemicals that do not naturally occur! CFCs are manmade - they are no naturally occuring CFCs.
The hazards we now associate with CFCs were discovered in the 1960s when a British chemist (Lovelock) was interested in tracing the motions of air masses. He was using CFC's to do so, as they were ideal for tracing air motions, being chemically stable and not naturally-occurring (they are only man-made) so their presence in an air mass could not be confused with CFC's coming from natural sources.
Perhaps you are thinking of the theory that volcanic chlorine caused ozone depletion? There are a number of problems with this:
(1) There was significant O3 loss in the 1980's, but no major volcanic activity then.
(2) There has been major volcanic activity since O3 monitoring began in the 1950's, but it was not necessarily associated with declines in O3. That is, O3 losses and volcanic activity appear to be uncoupled in time (lack temporal consistency)
(3) Measures of hydrogen chloride in the stratosphere after the relatively recent eruptions of Mt. Pinatubo and El Chicon showed less than a 10% increase in stratospheric HCl following those eruptions, while stratospheric HCl has increased steadily across recent years. Furthermore, it is estimated that 1% of the Cl released by the eruption of Mt. Pinatubo Cl made it to the stratosphere, judged by the increase in HCl in the stratosphere following the eruption and the estimated release of Cl by the volcano.
(4) Stratospheric hydrogen fluoride has also increased steadily in parallel with HCl, as would be consistent with CFC sources.
(5) Much of the HCl produced by volcanoes (or Cl from sea salt) is injected into the troposphere and very little of that makes it to the stratosphere, as it is washed out first. Volcanic emissions include abundant water vapor, and HCl and NaCl are quite soluble in water, while CFC's are not.
(6) Most of the HCl that does make it to the stratosphere is rapidly washed out -- that is the major removal mechanism for Cl from the stratosphere.
(7) After volcanic eruptions, scientists find enriched sulfate in ice caps, suggesting that the eruptions inject sulfate into the stratosphere, where it gets widely distributed before being washed out. However, ice caps are not enriched with Cl following volcanic eruptions, suggesting that most Cl doesn't make it to the stratosphere where it could get dispersed as sulfate does.