The changes are unpredictable - and THC is one of the many factors potentially involved - see chapter 3. Indeed, according to Chapter 3 of the NAS report a major problem with the THC theory is that it would result in a localised cooling rather than the more generalised cooling the data suggests.
'As discussed in Chapter 2, the Younger Dryas is the most studied example of an abrupt change and provides insights about possible mechanisms. In many ways the Younger Dryas serves as a defining event that embodies the notion of abrupt climate change. Heinrich and Dansgaard/Oeschger events are generally thought to be governed by physical laws that are closely related to those involved in the Younger Dryas; indeed, many consider the Younger Dryas to be just an unusually big Heinrich or Dansgaard/Oeschger event. However, there are potentially many types of abrupt change, as described in Chapter 2, so we need to consider the full array of possible processes, rather than only those currently in favor for explaining the Younger Dryas and Dansgaard/Oeschger events.' 'These examples suggest that abrupt climate change can occur in (at least) three fundamentally different ways: Abrupt climate change can be the response to a rapidly varying external parameter or forcing. If one views only the atmosphere-ocean system, massive sudden discharges of freshwater from disintegrating ice sheets on land would be an example of a sudden external influence. Nonlinearity in the atmosphere-ocean system is not a prerequisite for such behavior, whose time scale is dictated essentially by that of the forcing. Slow changes in forcing can induce the crossing of a threshold and result in the transition to a second equilibrium of the system. The evolution of such a change would be governed by the system dynamics rather than by the external time scale of the slow change. In considering the whole earth system rather than just the oceans and atmosphere, massive discharges of freshwater from disintegrating ice sheets would be a result of threshold-crossing. Slow melting at the end of the last ice age produced ice-marginal lakes. When the ice margin reached a particular location, such as the path of a former river that the ice had dammed, a threshold was crossed, the ice dam broke, and the water was released rapidly (Broecker et al., 1988). Regime transitions can occur spontaneously in a chaotic system. In this case, external triggers for transitions are not required, so a series of regime changes could continue indefinitely or until slow changes in external forcing or system dynamics removed the chaotic behavior.' You are looking at the big changes exclusively. It is the 'smaller and less persistent' abrupt changes that has political implications which you are continuing to not understand. You simply continue to call me a 'denialist' ignoring the data. Forget global warming. If unpredictable abrupt changes leads to a lack of warming or even a cooling - there will never be a case in the mind of the general public for reducing CO2. This may already be the case. >From my perspective - it is the result of otherwise well meaning and intelligent people making simple connections and then assuming that this was the entire explanation for a horrendously complex system on which we have the most partial and conflicting science imaginable. There are so many examples of scientific hubris in history that a whole school of philosophy of science arose to warn us against this. I don't think I'm blind - I think I have one eye in a world of the blind. Maybe I flatter myself. On Apr 23, 8:59 am, Eric Swanson <[email protected]> wrote: > Robert, > > Since you steadfastly refuse to discuss the issues I raised, I think > you should not refer to me as "the problem". I certainly recognize > the facts about abrupt changes in climate as found in the paleo data. > However, these changes, such as the Younger Dryas event, while > interesting, have no direct bearing on the present situation, since > the cause of the YD event no longer exists. Your reference to the NAS > report clearly points this out, if you would care to read Chapter 3. > > Also, the abrupt changes discussed are not the result of chaos within > the atmosphere/ocean climate system, but other ituations. Since they > were not, you must not use them as examples of potential abrupt > changes which we may presently face. However, the mechanism within > the climate system which resulted in the YD cooling appears to be the > Thermohaline Circulation, which can be a cause of future abrupt > changes, but thru other forcings, such as the slow freshening of the > surface waters of the Nordic and Labrador Seas. > > But, you don't appear interested in that problem, even though it was > discussed in the NAS book you linked to. Curious, isn't it? You > claim to be worried about abrupt climate change, yet are ignoring the > most likely path by which such might happen. Skepticism doesn't allow > one to ignore the data, which is what the denialist tend to do. > > One wonders why it is that you are so worked up and yet remain so > blind. Haven't you read Chapter 4 of the NAS report? > > http://www.nap.edu/openbook.php?record_id=10136&page=107 > > What sort of abrupt changes are you worried about? > > E. S. > ----------------------------- > On Apr 21, 11:01 pm, Robert I Ellison <[email protected]> > wrote: > > > > > > > I don't know how much clearer 'the science' can get - but unless > > people start understanding abrupt change in the climate system the > > 'inevitable surprises' are going to continue to undermine rational > > emmissions control. I am not the problem here. Eric is the problem > > with a dogmatic and rather silly insistence of Holocene climate > > stability, David is the problem with a confident, unsupported and > > misguided insistance that the conditions for abrupt change no longer > > hold, you are the problem because you have no appreciation of > > scientific uncertainty, the limits of knowledge or the value of > > scientific scepticism. You merely insist that I don't take climate > > change seriously because of some unspecified bits of properly > > formulated science - hardly a conceptually dense > > proposition. > > > We need to move on but cannot. I was wondering if step by step > > education of activists might be the way to permeate the zeitgeist with > > an abrupt climate change meme. It does seem to be righter than the > > stable climate idea and is a sceptic standard - albeit with a > > different risk assessment than that of US National Academy of Science > > quoted above. So it is not really a difficult concept if the sceptics > > get it. I don't understand the resistance to this idea at all - other > > than with vague notions of cognitive dissonance - but it is resistance > > that is not well founded. > > -- > 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 > athttp://groups.google.com/group/globalchange- Hide quoted text - > > - Show quoted text - -- 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. 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