Subject: FWD: "The Great Climate Flip-flop" Date: Wed, 10 Dec 1997 07:01:40 -1000 From: "Jay Hanson" Organization: GST Data Services, Inc. Newsgroups: sci.environment, sci.energy, sci.econ ----------------------------Original messagee---------------------------- >My cover story for The Atlantic Monthly's January 1998 issue is about >climate flips and how they might be triggered by our current global >warming. "The Great Climate Flip-flop" is now available at > http://WilliamCalvin.com/atlantic >and its bibliography is at http://WilliamCalvin.com/climate >We now know that global climate can undergo a very rapid change in just >a decade. Abrupt coolings and warmings happened dozens of times in the >last ice age, and a severe cooling even occurred during the last warm >period like today's (another one ended it). It seems likely that >CO2-induced greenhouse warming could trigger another >such episode, which would be a far more serious problem than the >greenhouse concerns thus far identified. > > William H. Calvin Calvin@WilliamCalvin.com > University of Washington http://WilliamCalvin.com Hi, Thanks for the reference to a very interesting article. It is items like this that make the net worth the trouble. I think it well known from various sources that the climate has "switched" between a "warm" and a "cold" state at least several times during the Pleistocene resulting in 4 glacial periods separated by three extended warm periods (and we are in the 4th warm one now). While the transition between these states is "fast" on a geologic time scale, it is not clear that it is fast on a human scale. But I think his idea that in increase in warming due to increased CO2 can/will be the "trigger" for the next ice age is unlikely. I would bet the exact opposite. To refresh our memories on "recent history": a period of glaciations started about 20 million years age. No generally accepted reason as to WHY. The Himalayan mountains were formed starting about 25 million years ago, as the result of a collision between two of the "drifting" plates on the earth's surface. There has been some speculation that these two events are related: that the rise of the mountains CAUSED the ice ages. But the first attempts to explain just how, based on changes in air circulation caused by the new mountains, could not (using computer models) cause enough of a change in climate to do the job. But the models did indicate that enhanced monsoon rains in southeast Asia are due to the Himalayan mountains. Could the greater rain eroding the newly exposed mountain rocks have caused the ice ages? If you watched the Nova program on Cracking the Ice Ages, recall that the attempt to explain the connection between the glaciation and the rise of the mountains failed when the model was based just on the air circulation changes. Right DIRECTION, but the effect was much too small. It was only when loss of CO2 due to the weathering of the mountains was introduced into the model that glaciation was predicted. (I don't recall that they even said whether or not they included the water-vapor amplification factor). Far from a 3rd order or side effect, CO2 is a major player. Erosion of the newly exposed rocks removes CO2 from the atmosphere, by chemically reacting with it. About a hundred years ago chemist Savante Arrhenius had proposed that reduced atmospheric CO2 could cool the earth enough to cause an ice age, and that increasing the CO2 level could end the ice age. But he had no explanation of what would/could cause the CO2 level to change. He suggested maybe the weight of the ice caused volcanic eruptions, and the CO2 from them caused tropical plants to grow and consume the CO2. But that didn't sound very convincing. But with the acceptance of Plate Tectonics during the 1960's there is a mechanism to explain the glaciations. Plate collisions make new mountains, and their erosion sucks the CO2 from the atmosphere, cooling the earth and triggering an ice age. But the "cold" (low CO2) state kicks over into "short", unstable warm spells of about 15,000 year duration. We are in (near the end!) of one of these now. But by this analysis, far from trying to REDUCE greenhouse gases, we should be trying to increase them, to stave off a return of the next glaciation that the Pleistocene will soon be throwing at us. Note that these major glaciations are not the same as the various "little ice ages" that I discuss in my web page file "CO2 and Global Warming", but the Calvin article does provide a possible link between them. Maybe the "little ice ages" of recorded history, and the bigger ones of 12,000 and 8,000 years ago, were the "chatter" that the unstable "warm but low CO2" state is showing as it prepares to flip back to the "cold low CO2" state. Maybe we need to get the earth into the "warm high CO2" state that IS stable. If we have to pick between "glaciation" and "global warming", then for most people, it's "go for the warm". And note that not every expert in this field thinks CO2 is a problem. Richard S. Lindzen for example, and he is the Alferd P. Sloan Professor of Meteorology at M.I.T. ,,,,,,, _______________ooo___(_O O_)___ooo_______________ (_) jim blair (jeblair@facstaff.wisc.edu) Madison Wisconsin USA. This message was brought to you using biodegradable binary bits, and 100% recycled bandwidth. Subject: Re: FWD: "The Great Climate Flip-flop" Date: Wed, 10 Dec 1997 18:05:15 -0500 From: "J. Preston Bye" Organization: Erol's Internet Services Newsgroups: sci.environment, sci.energy, sci.econ Climate can change swiftly going from warm to cool in a period of about 20 years, as you point out. Broecker has a theory that it is ocean circulation changes that cause these climate changes and he may well be right. Whatever the reason, one should carefully study Broecker's Figure 3 in his Science paper. All of the big abrupt changes occur when the climate is initially cooler than present except for one very small excursion that occurs about 8000 years ago (this excursion is about 25% of the size of the other excursions). During the interglacial periods, such as the one we are living in now, the variations in climate are very much reduced. At the end of the last interglacial, called the Eemian, there was a long gradual decline in temperatures followed by an abrupt (20 year) cooling event that started the ice age. The present interglacial has shown the same long term gradual cooling (as shown in Broecker's Figure 3). To me this suggests that the abrupt climate changes are more probable and more severe when the climate is colder. This line of reasoning argues that a cooling could be dangerous and if there is a way to avoid such cooling, then it should be pursued. Perhaps greenhouse gases are warming the Earth and this warming is preventing another abrupt climate cooling from occurring. The empirical data strongly suggests this scenario is true. Just some food for thought.