Robert, You seem to be missing the point. Short term and locally, weather appears chaotic. Longer term and globally, climate is much more stable.
Your previous reference to the Younger Dryas period is one example. The cause of that event has been almost nailed down to being the result of the flooding of the North Atlantic by one or more melt water pulses as the lakes trapped behind the melting glacier broke thru to the ocean. Yet, you seem to think that this is an example of chaotic behavior of climate, when the cause is well documented. That cause is gone and can not be repeated in today's world. However, a similar result may obtain as the result of other mechanisms which freshen the waters in the Nordic Seas. That may lead to a threshold type shutdown in the THC. Rind mentions this, if you read his commentary. Newer information about the THC suggests that there is some short term variation in the strength with time, which adds another variable as a possible cause of the atmospheric variation which you seem to think is purely unknowable chaos. On Jan 29, 8:28 pm, Robert Indigo Ellison <[email protected]> wrote: > It is very difficult to forecast abrupt climate change and there are > no precise techniques. But there are equilibria – states that tend to > last for 20 to 30 years - or interannual shifts such as ENSO. Thus it > can be said that the current ‘cool planet’ phase might last another > decade or 2. It is a matter of assuming that the next climate shift > will occur with a quasi regularity. > > There are repeated challenges in this forum to identify scientific > departures from the so called ‘consensus’. There is a whole field of > science that says that climate is dynamic and nonlinear – classically > ‘chaotic’ – rather than simply driven by ordered forcing. > > Have a look at the Rind (1999) article ‘Climate and Complexity’ I have > linked to on the site: > > http://pubs.giss.nasa.gov/docs/1999/1999_Rind_1.pdf > > “Is the climate system “complex,” and does it matter for long-range > (decadal-scale) climate forecasts? The answer to the first question is > definitely “yes”; the very concept of complexity originally arose in > concert with atmospheric processes. To the second question, we have to > answer “we don’t know.” If it is important, it will just make > predictions of the anticipated climate change of the next century that > much more difficult." > > "Questions concerning the future climate in general will probably > continue to be dominated by uncertainties in the radiative feedbacks. > These feedbacks may be influenced by the system’s nonlinearities and > the future patterns of variability, but we do not know by how much. On > the regional scale, the nonlinearities might play a larger role; they > also might be extremely difficult to forecast. Climate, like weather, > will likely always be complex: determinism in the midst of chaos, > unpredictability in the midst of understanding.” Note that Rind does not say climate it is not possible to determine climate, only that it is more difficult to decipher climate on a regional scale. Given our understanding of the historical data, much of the long term climate variability can be attributed to single events, such as the rate of volcanic eruptions. And, we know that the Earth underwent a basic change in climate around 3 million years ago, thus the climate of previous years, while interesting, may not tell us much about our present system. > In 2010 some of us know the answer to the second question. So far, you have not demonstrated that you have such an answer, only asserting without proof that past climate looks to be chaotic. Their indices are not predictive, as near as I can say, since they do not include any physical reason for the variations. Tsonis and Swanson's work does not get to the root cause of their presumed correlations. They mention volcanic eruptions, which has a well defined impact, but do not attempt to remove their short term impact from the long term data sets they which they compare. There's little support for their claim that the Earth is in a period of cooler conditions, indeed, the Arctic sea-ice trend is pointing to further decline in the yearly minimum at the end of the melt season. Did you view Alley's AGU lecture yet? He discusses many of the questions you have thrown out. http://www.agu.org/meetings/fm09/lectures/lecture_videos/A23A.shtml E. S. --- -- You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/globalchange
