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uk.sci.weather (UK Weather) (uk.sci.weather) For the discussion of daily weather events, chiefly affecting the UK and adjacent parts of Europe, both past and predicted. The discussion is open to all, but contributions on a practical scientific level are encouraged. |
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#1
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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 |
#2
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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..... |
#3
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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 |
#4
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![]() "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 |
#5
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![]() "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. |
#6
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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 |
#7
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![]() "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. |
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