REPLY Climate change (SD6242)

[System Dynamics Mailing List]

Posted by  Tom Forest <tforest at prometheal.com>

With respect to David Corbin's advocacy of a MUCH longer timeframe for the 
model, and notwithstanding my affection for such models, I think that the 
dynamics of interest here are indeed captured in the geologically 
minuscule intervals of human lifetimes: punctuated equilibria. In 
particular, there is a loop dominance shift that takes places in ten years 
or less, according to the ice core samples from Greenland among other 
sources. David says "This fact alone should set alarm bells ringing for 
any system dynamicist worth their salt." Speaking of salt, in "The 
Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future," 
(Princeton University Press, 2000 ISBN 0-691-10296-1) Richard B. Alley 
discusses the global thermohaline circulation as a keystone to our current 
balmy interglacial. It is possible that human-caused global warming will 
turn off the thermohaline circulation and plunge us into the next full 
glacial--the most counterintuitive of outcomes for global warming but the 
sort at which SD excels in illuminating. On p. 110-1, describing the 
"Younger Dryas, the last cold gasp of the Ice Age between about 12,800 and 
11,500 years ago," Allen says of changes in the ice cores at the end of 
that period that they are "most directly interpreted as a twofold change 
in three years, with most of that change in one year, and with a 'flicker' 
when the climate bounced up and down." By that he means that the Greenland 
snow levels typical of cooler climate shifted to those typical of warm 
climate in three years or less.

I also think that mass extinctions (Permian/Triassic, Cretaceous/Tertiary, 
and the human-influenced Pleistocene/Recent) are driven by finely-grained 
transition dynamics, and am working on a model to articulate that point.

David, if you want to build a long timeframe model, Alley's book is a good 
starting point. I'd like to see it, and will help if I can!

Tom Lum Forest
Forest Grove, Oregon
Posted by  Tom Forest <tforest at prometheal.com>
posting date  Mon, 5 Feb 2007 13:58:25 -0500