Dear Eric, The science consensus supports the notion of earth climate as a complex and dynamic system at scales ranging from ENSO to ice ages and beyond. The answer to the first question of Rind - you recall - is emphatically yes. Climate bounces around like a spinning top on a rough surface. There are multiple equilibria - multiple point (b)'s in the simple mechanical analogy - and constant more or less eccentric departures. I am afraid climate is not stable at all - but there does seem to be some consistency with ocean temperature +/- 5 degrees keeping the planet survivable.
I sure you can do it - forget simple cause and effect and a single cause for every event. Imagine energy cascading through the cyrosphere, atmosphere, hydrosphere and biosphere. The earth climate system doesn't respond simply to a single factor - there are mulitple feedbacks operating simultaneaously and many degrees of freedom. Adams 'cascade of powerful mechanisms'. Small changes in initial conditions cause system flucuation - or abrupt change in the sense of the National Academy of Science definition of being out of proportion to the initial forcing. There is an interesting read at the QEN - http://www.esd.ornl.gov/projects/qen/transit.html - already linked to. The Younger Dryas is one amongst many warming and cooling periods in the Quaternary with multiple possible contributing factors. I have described Tsonis' climate shift papers in some detail - nothing to do with causal links at all and everything to do with synchronous chaos. Forget Tsonis for a while - try reading some stuff on ENSO variability - particularly the 1976/1977 'Great Pacific Climate Shift' - and get a feel for real physical variability in oceans. There is plenty about on the internet. The 'averaging' of the evolution of global temps only ever worked (and this was known going in) if there was no abrupt climate shift in the interim. There is nothing new in Alley's lecture - assume I have looked at anything linked to in discussion and if I don't respond I simply can't be bothered disccussing it. I have fixed a link and added some resources - http://www.earthandocean.robertellison.com.au/ You should make this paradigm shift from simple cause and effect to complex systems in order to more correctly imagine global climate outcomes. I included the Rind link because it is a good and simple explanation. Read Rind again and Adams at the QEN site. You don't have to accept that climate is 'complex' - it would be a bit of a flat earth stance but not my problem. Cheers Robert On Jan 30, 12:57 pm, Eric Swanson <[email protected]> wrote: > 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. 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