Best wishes
Keith
An important point which often gets missed is that we are adding to the
atmosphere gases of known properties: they cause the atmosphere to retain
heat.
And, if the atmosphere didn't already contain gases which retain heat,
the Earth would be very much colder than it is.
There are many secondary effects of adding these gases; but for the last
140 years of calculations, the secondary effects tend to balance out and
the net effect resembles the primary effect.
There is a separate question which is: is there a trend of actually
increasing temperature of the Earth's surface, due to the gases we have
added, detectable through the normal variation of weather year to year.
In 1988 Dr, James Hansen said yes, and since then his opinion has become
the scientific consensus as more and more information has come in and more
analysis has been done.
As of 1988, Environment Canada estimated that CO2 was responsible for
about half of the total warming influence of gases added to the atmosphere
by humans. As I recall, flurocarbons like Freon, and its chlroflurocarbon
replacemnets, accounted for about a quarter, wuth methane and some lesser
gases providing another quarter. I surmise that CO2 probably accounts for
more than half now, as methane losses in the former Soviet Union have
reportedly decreased considerably.
A rough chronology of climate science and CO2 goes something like this:
1824 - Fourier in France pointed out that the atmosphere must be retaining
heat.
1858 - John Tyndall in Britain made the first measurements of the heat
retaining properties of CO2 and water vapour.
1862 - Tyndall published and pointed out the role of these gases in
retaining heat in the atmosphere.
1898 - Svante Arrhenius (Sweden) pointed out the burning coal might
eventually modify the climate through CO2 emissions
1920's - Milankovic (Serbia) published his calculations on the effect of
cycles in the Earth's orbit on climate.
For more see
Simple models of climate (history)
http://www.aip.org/history/climate/simple.htm
Bibiliography
http://www.aip.org/history/climate/bibdate.htm
Books
Global warming: the complete briefing
by John Houghton
Cambridge University Press, 2nd edition 1997
Our threatened climate: ...
by Wilfrid Bach
Dordrecht, Boston: D. Reidel Pub. Co. (Kluwer Academic), 1984
The Ages of Gaia
by James Lovelock
1988
It's true that the Earth's climate is a complex and ill-understood system.
The evidence of past climates has shown wide variations, some extremely
fast and "turbulent". It seems that climate may have a couple of extreme
states between which it oscillates. Human imfluences are superimposed on
this "natural" variation. Buildup of peat and methane hydrates in cold
periods may tend to provide the wherewithal for prolonged increase
of temperature once it exceeds some critical value. The Sun is very
gradually increasing its heat output and the long term trend of Earth's
temperature appears to be up. This may eventually put an end to life on
Earth even before the Sun's expected red-giant phase. To me it doesn't
seem like a good idea to try to hurry this process along, but this is
what "business as usual" is doing.
As Dr. Wallace Broecker has put it, "The climate is an angry beast,
and we are prodding it with sticks."
Doug Woodard
St. Catharines, Ontario, Canada
On Wed, 23 Feb 2005, Greg Harbican wrote:
[snip]
> I personaly am not 100% sure, that CO2 and other green house gasses are the
> cause of global warming, in fact that I am totaly 100% certian about global
> warming, because I perceve ( correcly or incorrectly ) varables, that I
> don't know have been accounted for. I am not saying that I am a better
> person, amd know more, than the scientest that support the theory of global
> warming. I just have lingering doubts, because I know the mistakes that
> science makes, and after all the science of global warming is
what, 10-15 or
> so years old? OTOH, I am sure, that there is currently a disturbing
> trend, that needs to be delt with, be it short term or long term.
[snip]
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