Although there is very little ozone in the stratosphere it is a vitally important trace gas. Its role in filtering out ultraviolet radiation from our sun is well known, but by adsorbing ultraviolet and longer wave radiation, it also warms a part of the atmosphere which would otherwise be extremely cold.
The warmer stratosphere forms an inversion layer over the colder part of the upper troposphere acting as a structure, a top, or a kind lid, on the air below. As ozone has been measured disappearing, more ultraviolet rays from the sun are believed to be penetrating further down into the atmosphere taking warmth along. For a number of reasons, including natural variation, changing levels of sunlight, clouds, and fear of losing grants, scientific confirmation of an increase in ultraviolet radiation is lacking.
Since ozone is important to the energy balance of the stratosphere, any change in its concentration should also change the structure and climate of the stratosphere. And, if the stratosphere changes, the lower atmosphere, the troposphere, and our weather systems, should also change. Easy to say, hard to show.
A recent study shows the decline in stratospheric ozone and temperature over the last eleven years are related based on an analysis of measurement by U.S. scientists. "Nature: the international journal of science", Volume 382, #6592 "Fingerprint of ozone depletion in the spatial and temporal pattern of recent lower stratospheric cooling."
What is so striking about this study is that it appears to demonstrate an effect of human activities within a very short time scale: that is, just eleven years. There is no detailed discussion as to what and how much this change is related to changes in weather and climate as we experience it where we live.
When geoscientists, who usually work within time frames of millions of earth years, talk about "rapid change" they usually mean over several centuries. The ozone layer is at least a thousand million years old. The interminable Global Warming wrangling is framed in a time period of 50 to 100 years. Now, the measured cooling of the stratosphere in 10 years comes as something of a disturbing surprise. The problem is here-right now- today-and it cannot easily be ignored !
Linking ozone depletion with climate change has never been promoted in the popular press, or, for that matter, scientific journals. The ozone layer has been represented as something static, as a "protective shield against harmful ultraviolet radiation." The concept of a "top" on the lower atmosphere was first mentioned by the English Science writer John Gribbin in his book "A Hole in the Sky" (Bantam, 1988), but this effect was ignored and overshadowed by concerns that the build up of heat trapping or greenhouse gases would induce disruptive climate changes in from 50 to 100 years.
While the last twenty years have included the warmest on record, accurate records date back only a 150 years, and there is no way to determine if the warming is not the result of some natural variation or trend. Warming has occurred, but the average is small, and averaging something as complex as or earth's weather is daunting. It is hard to connect changes with human activities. But with ozone depletion, the case is clearer.
What the scientists have done is to feed the measured decline in ozone into an established computer model that simulates the atmosphere. They found the model's results compare well with the actual measurements. They can also continue to update and refine their model.
In another study, scientists at Imperial College U.K. report on ozone depletion and stratospheric cooling and its effects, in Geophysical Research Letters (Nov. 1, 1996). These articles may indicate that the recognition of the role of ozone depletion in climate change is itself changing.
What effect these changes in the vertical temperature structure of the atmosphere have on our weather at this point is open to speculation. The large scale movements of rising and descending masses of air defines our weather and, our weather over time, defines our climate.
CFCs warm the lower and help cause cooling of the upper atmosphere. Ozone is a pollutant heater and irritant in the lower and a "shield" and "heater" in the upper. Large numbers of commercial jet aircraft fly near the structural boundary of the upper and lower atmosphere. When they are all added up, it would seem obvious to anyone, even a freshman Republican, that the earth's life support system has to change in some way-and the changes may be disruptive.
Scientists expect to be able to observe the "recovery" of the ozone layer in the coming years if the restrictions on the production and use of CFCs are obeyed. However, a multi-million dollar illegal trade in heat trapping and ozone destroying CFCs continues to grow in the U.S. Smuggling these substances is now surpassed only by the importation of illegal drugs (New Scientist, 26, October, 1996).
But if our atmosphere is, or will soon enter recovery, there does not appear to be an honest assessment of how we got here, no sincere acknowledgment of a desire to reform, no reparations and certainly no pledge to abstain from the destructive practices which got all of us in this jam.
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