Robert, I'm very much concerned about the possibility of rapid climate change. So are many others who study climate. The ultimate question is, are we in the process of CAUSING such a dramatic shift and,f if so, could such a major shift be prevented or even reversed?
Robert Indigo Ellison wrote: > 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. Climate has been relatively stable over the Holocene. Of course, we know that there were repeated periods of colder conditions called Ice Ages. this might lead one to conclude that there are only a few stable conditions, that is, Ice Age or Not Ice Age. The problem is, what if increases in CO2 in some way CAUSE the Earth to flip back into the Ice Age condition? > 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. One reason that apparently small changes, such as the Milankovitch orbital variations, produce larger changes is the apparent positive feedback within the climate system. http://en.wikipedia.org/wiki/Milankovitch_cycles Alley discusses this in some detail in his lecture to which I pointed. Do you agree with his emphasis on CO2 as the driving mechanism for those changes? If so, why would you not be worried about mankind's increasing emissions of CO2 and other greenhouse gases? > 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. The Adams paper is dated 1999 and is a bit out of date with respect to the latest findings. Here's a link to a PDF of the paper, which is a bit easier to read: http://ethomas.web.wesleyan.edu/adamsetal99.pdf The Younger Dryas started with a well known single event, a flood of fresh water related to the melting of the glaciers over Canada. That event is not repeatable in the present situation, thus it is not part of some chaotic oscillation, or what ever you are trying to claim it is. That said, there appears to be an ongoing change in salinity in the Nordic Seas, which may result in a shutdown of the THC. It is thought that the abrupt climate change seen in the Younger Dryas switch was the result of a shutdown of the THC. Therefore, it is reasonable to assume that should the freshening of the Nordic Seas continue, which is likely to be a result of global warming, could produce another cold period similar to the Younger Dryas event. I think that the Younger Dryas event should be taken as a warning of the potential danger hidden within the problem of AGW. 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
