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Politics : The Environmentalist Thread -- Ignore unavailable to you. Want to Upgrade?

To: Thomas A Watson who wrote (12580)	5/16/2007 1:40:47 PM
From: maceng2	Read Replies (2) \| Respond to of 36918

Here is one of the "climate myth" links you definely need to read. Climate myths: Chaotic systems are not predictable 17:00 16 May 2007 environment.newscientist.com NewScientist.com news service Michael Brooks You cannot predict the exact path a ball will take as it bounces through a pinball machine. But you can predict that the average score will change if the entire machine is tilted. Similarly, while we cannot predict the weather in a particular place and on a particular day in 100 years time, we can be sure that on average it will be far warmer if greenhouse gases continue to rise. While weather and to some extent climate are chaotic systems, that does not mean that either are entirely unpredictable, as this demonstration neatly illustrates. The unpredictable character of chaotic systems arises from their sensitivity to any change in the conditions that control their development. What we call the weather is a highly detailed mix of events that happen in a particular locality on any particular day – rainfall, temperature, humidity and so on – and its development can vary wildly with small changes in a few of these variables. Climate, however, is the bigger picture of a region's weather: the average, over 30 years (according to the World Meteorological Association's definition), of the weather pattern in a region. While weather changes fast on human timescales, climate changes fairly slowly. Getting reasonably accurate predictions is a matter of choosing the right timescale: days in the case of weather, decades in the case of climate. Dynamic interactions Climate scientists sometimes refer to the effects of chaos as intrinsic or unforced variability: the unpredictable changes that arise from the dynamic interactions between the oceans and atmosphere rather than being a result of "forcings" such as changes in solar irradiance or greenhouse gases. The crucial point is that unforced variability occurs within a relatively narrow range. It is constrained by the major factors influencing climate: it might make some winters bit a warmer, for instance, but it cannot make winters warmer than summers. Put the other way round, two or three warmer winters in a row could be due to unforced variability rather than global warming, just as two or three high scores in pinball do not necessarily mean the table is tilted. But the more warmer winters there are, or more high scores there are on a certain pinball machine, the less likely it is to be due to the chaos inherent in the system. To account for the influence of chaos, climate scientists run the models repeatedly, with slightly different starting conditions. The difference in outcomes gives scientists an indication of the uncertainty in any given prediction, of the range of possible outcomes.