"Dave Ludlow" wrote in message
news
On Mon, 13 Oct 2003 15:52:59 +0100, "Alastair McDonald"
k wrote:

If I am correct we are not at the end of one of those phases. We are at
the beginning. Climatic disasters will continue to occur each year until
the Arctic ice has gone completely and the climate has settled into a
new patern of clouds.

Playing devil's advocate, do we understand these processes so well
that we can discount the following scenario?

Melting ice/increased wv/ increased global temperatures prompt a much
more rapid increase in cloudiness than anticipated, a cloudiness
"flip" or overshoot, if you lke. This quickly increases the overall
albedo, overwhelming the initial relative warmth... and is followed by
rapid global cooling.

--
Dave

IMHO the scenario you suggest is impossible. If increased
cloud causes cooling, then the Arctic ice will reform and the
system would return to the state it was in before, not to a
cooler state. Moreover we know from Antarctic ice cores
and deep sea sediment cores that global temperatures
during the last interglacial were warmer than today, and in fact
warmer than at any time during the Holocene. Therefore I
think it is safe to say that there is no reason to believe that
increased cloudines will protect us from rising temperatures
initiated by increasing the greenhouse gas concentrations.

OYOH you are correct to say we don't understand these
processes well. That is why I did not claim that clouds will
increase because temperatures increase. What I did write
was that the temperatures will increase until the clouds
increase. If the cloud does not increase, the oceans will boil
away. Since this has not happened in the past it is
unlikely to happen in the near future, I hope! So I am arguing
that the clouds will increase, probably when the Arctic polar
vortex is no more. In other words when there has been a major
reorganisation of the climate system, with the Ferrel cells
disappearing because there is no longer a source of cold air
in the Arctic to undercut and lift them.

It ia all quite simple really. The reason no one has thought of
it before is because it is unthinkable!

Cheers, Alastair.