"Bjørn Sørheim" wrote in message
...
On Wed, 15 May 2013 10:18:42 +0100, "Alastair McDonald"
wrote:
.
.
.

But there is a greater danger. Here you can see another chart of
temperature
against CO2 over the last 600 M yrs
http://deforestation.geologist-1011....mperatures.png
where the temperature makes step changes. That is my concern. Will CO2
pass
a tipping point where after a period of stability the global temperature
then jumps into a new extreme state.

What is causing the the leveling around 22C when the CO2 level
reaches very roughly 1000 ppm or higher? Why don't further increases
rise the temperature any higher?
Is it all snow/ice gone therefore no possibility to further reduce the
reflection of solar energy into space by white surfaces?

Bjørn Sørheim


Where did you read that global temperatures would reach 22C at 1000 ppm
concentration of carbon dioxide (cCO2), and then go no higher even if cCO2
continued to increase? I have not heard that before.

However, the CO2 band is saturated, which should mean that if cCO2 increases
then no more heat will be trapped. In fact the band is made up of a series
of lines and although each line is saturated when cCO2 increases the lines
become broader and the space between the lines becomes narrower so more heat
IS trapped. Eventually the spaces all become filled in and the more heat is
only trapped at the edges of the band.

There has just been a paper published in Weather, the monthly magazine of
the UK Royal Meteorological Society, where they showed that a weak CO2 band
in the IR window would become effective at about 10,000 ppm cCO2.
http://onlinelibrary.wiley.com/doi/1....2072/abstract
But that is another story.

I can't comment much further without knowing your sources, which, even if
you could only give me a clue, I would be very interested in investigating.

Cheers, Alastair.