With ice sheets evidently on the move in the Arctic and Antarctic - in
terms of moving from one area to another - it occured to me on the way
into work today that surely deserts must do the same and there must be
accounts from subsistence farmers in the central African basin with
accounts that...
"The Sahara desert used to start here - now this area is well
irrigated and is being reclaimed by the savannah / jungle - the desert
is now three miles further north..."

During some research I came up with this very interesting ...


Here is an extract from the article...

"Historical climate research indicates that climate change does not
follow a pattern that people seem to expect (the climate always
gradually and slowly changing over the course of a long time). Rather,
the evidence indicates that the planet can suddenly flip from one
climatic condition to a new equilibrium in about ten years. (so then
climate change can be said to resemble the flipping of the earth's
magnetic poles, which also takes place abruptly). What this suggests
is that climate change only requires that the ecosystem reach
'critical mass' and then the 'climate flips' and the world reaches a
new equilibrium and a new climatic state prevails.

The accumulating evidence I have been gathering suggests that this
process is now underway. Research indicates that enough CO2 has been
released into the atmosphere over the last century to raise the global
temperature between one and two degrees. The result is that the
climate is now unstable, and therefore we are in the midst of one of
those sudden decade long climate shifts. In fact, given the increasing
tempo of change taking place on the Sahara (the signal environment) we
are actually coming up to the end of this ten year period, and in the
immediate future the climate will become stable in new equilibrium."

You'll find the full text at...

http://southafrica.indymedia.org/news/2003/09/4551.php

Very off topic in terms of UK weather - but I wondered if anybody has
any comments on this.

Cheers,

Scott Whitehead

There is now growing momentum to the theory that climate in the past has
gone through dramatic and abrupt shifts, 10C changes in 10 years, which puts
our 1-2C changes over the last 150 years or so into some sort of
perspective. Maybe we are approaching one of these 'flips' soon, though I
feel that something dramatic has to happen first such as major volcanic
eruptions, to start the change in the first place. I doubt whether 1 to 2
degree increase in temperature over the last few hundred years is enough.

Also, time and time again, evidence is gained that the temperature of this
planet is directly affected by atmospheric carbon dioxide concentrations.
During ice ages, carbon dioxide levels were very low, conversely, during
warm periods, carbon dioxide levels were high. What causes these large
changes in CO2 concentrations, in my opinion, is still open to debate.

_________________________________
Nick

Wine is fine but whisky's quicker.....

On 13 Oct 2003 05:12:18 -0700, Scott Whitehead in
. com wrote:
snip

"Historical climate research indicates that climate change does not
follow a pattern that people seem to expect (the climate always
gradually and slowly changing over the course of a long time). Rather,
the evidence indicates that the planet can suddenly flip from one
climatic condition to a new equilibrium in about ten years. (so then
climate change can be said to resemble the flipping of the earth's
magnetic poles, which also takes place abruptly). What this suggests
is that climate change only requires that the ecosystem reach
'critical mass' and then the 'climate flips' and the world reaches a
new equilibrium and a new climatic state prevails.

snip
Very off topic in terms of UK weather - but I wondered if anybody has
any comments on this.

This idea of a "sudden flip" was suggested by Edward Lorenz back in the
1960s. He never discounted other causes of climate change, but added the
*possibility* the atmosphere can exist in two (or more) stable states, with
a rapid transition between them possible. He cited the long forgotten
Fultz dishpan experiments, which simulated the long wave behaviour of the
upper troposphere in a rotating tank. Fultz found that at certain rotation
rates of the pan (analogous to the speed of rotation of the earth), both a
4 or 5 wave pattern were possible - each persisting for a long time until
there was some external disturbance. He found a flip from 4 to 5 and back
was possible. David Fultz died last year and here is a URL about his life:

http://www-news.uchicago.edu/release...31.fultz.shtml

--
Mike posted to uk.sci.weather 13/10/2003 12:42:09 UTC
Coleraine
Seeking information about the Internet and the way it works? - Subscribe to
news:uk.net.beginners

"Scott Whitehead" wrote in message
snip
Very off topic in terms of UK weather - but I wondered if anybody has
any comments on this.

If you'd just been digging in my garden what purports to be rich soil (lots
of compost added over the years), you could be forgiven for thinking that
the Sahara has reached as far as 52 degrees north.

So not off topic at all.

Jack

"Scott Whitehead" wrote in message
om...
With ice sheets evidently on the move in the Arctic and Antarctic - in
terms of moving from one area to another - it occured to me on the way
into work today that surely deserts must do the same and there must be
accounts from subsistence farmers in the central African basin with
accounts that...
"The Sahara desert used to start here - now this area is well
irrigated and is being reclaimed by the savannah / jungle - the desert
is now three miles further north..."


Snip ...

There is no doubt that the anonymous Christian writer is correct when
he states that;
"Historical climate research indicates that climate change does not
follow a pattern that people seem to expect (the climate always
gradually and slowly changing over the course of a long time). Rather,
the evidence indicates that the planet can suddenly flip from one
climatic condition to a new equilibrium in about ten years.

The transactions of a meeting held at the Royal Society to discuss this
matter have just been published. See;
http://www.catchword.com/rsl/1364503...0/contp1-1.htm

The meeting was organised by oceanographers, hence the emphasis
on switching of ocean currents as the cause of these rapid changes.
However, papers by Wood, and by Gildor & Tziperman both point
to the trigger being sudden ice sheet changes altering the global
albedo which in turn is then amplified by the greenhouse effect of
water vapour. The contraction of the Arctic ice sheet, which has been
dramatic during the last two summers, could well trigger yet another
rapid change.

Without the Arctic sea ice present during the summer, that region
will warm, leading to more evaporation, water vapour, and greenhouse
warming from the increased water vapour which will have a positive
feedback effect. The warmth from the Arctic will spread south, as
it has done this summer, and will cause global temperatures to rise.
This will lead to more water vapour globally and a global temperature
rise leading to an abrupt climate change. Temperatures will rise until
the climate regime settles into a new state where the cloud cover has
increased such that its new albedo equals the loss in albedo from the
lost Arctic ice, and the global heat balance is restored.

What this new climatic regime will be like is anyone's guess, but it
probably will entail widening of the tropical zone with the sub tropical
deserts moving towards the poles. This summer has seen fires
on the northern coast of the Mediterranean and in north America.
These could have been made possible by drier regimes in those
regions caused by the subtropical deserts stretching their influence
northwards.

The writer of the article you quote says;
... In fact, given the increasing
tempo of change taking place on the Sahara (the signal environment)
we are actually coming up to the end of this ten year period, and in the
immediate future the climate will become stable in new equilibrium."

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.

HTH,

Cheers, Alastair.

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

"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.