One thing that is clear from this thread is that there is a need to clarify the difference between ozone depletion and greenhouse effects.
Ozone (O3) exists in the stratosphere as a result of UV light interacting with oxygen molecules (O2). It was thoroughly documented about twenty years ago, that the ozone layer was being attacked by flourine ions that resulted from disassociation of CFCs in the UV at this altitude. As CFCs are extremely stable, except in UV light, any CFCs vented to the atmosphere eventually end up in the stratosphere. The ozone layer provides a shield that prevents most of the UV light from reaching the surface, and so is quite important from a human and animal health point of view. The problem was quickly recognised as being man made, and international action was rapidly taken to alleviate the situation, and production of CFCs has now virtually ceased, although it will take several centuries for all those in the atmosphere to work their way through the system.
The Greenhouse effect is a totally unrelated situation. The temperature of the earth is maintained at its current level by the greenhouse effect, where the atmosphere is less transparent to infra red radiation than it is to visible light, so that the earth's net radiation balance is positive. This effect is due to a variety of gases in the atmosphere of which the most important is carbon dioxide. The concern is that a manmade increase in the amount of carbon dioxide in the atmosphere will cause a rise in global temperatures.
Certainly, the amount of CO2 in the atmosphere has increased in the last two hundred years as a result of the industrial revolution, and there is also some evidence that it has increased over the last ten thousand years as a result of the development of farming.
There is also good evidence that temperatures world wide have increased in the last fifty years, and appear to be still increasing.
But that is about where the agreement ends. It is almost impossible to have any proof of worldwide temperatures further back than about fifty years, as data collection was not good enough. There are various ways of estimating temperatures in the past but they are all subject to various objections.
To try and see what is likely to happen in the future, computer models are constructed to match past temperatures and greenhouse gas measurements, and extrapolated into the future. The problems with these models are multiple - to run on existing computers they have to be a gross simplification; the historical data they are based on is suspect; the mechanisms that affect greenhouse as distribution are not well understood; all existing models largely ignore the southern hemisphere; and other problems.
Contrary to the general media presentations, Australia's contribution to greenhouse gas emissions are almost negligible - a result of the small population by world standards. Anything that could be done by Australians, even total depopulation and return to bush, would not make a significant difference, even though the per capita consumption is high, mainly the combination of a high standard of living plus relying on coal for power generation. Of comparable nations the US is higher per capita, and Europe lower, largely because of high energy prices and the use of nuclear power.
Despite this, reduction in greenhouse gas emissions would seem to make sense (largely as an example to the main contributors - US, China, India, Europe), although the most effective way to do this is not the obvious one.
For a start, the largest contribution to CO2 emissions is power generation - and the obvious way of reducing this is to reduce power usage - do without airconditioning by improving insulation for example, reduce purchases of new everything and so on - and increase the cost of power!
John
Last edited by JDNSW; 11th February 2008 at 08:35 PM.
Reason: Correct grammar
John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
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