Re: Ice Ages
pete (VINCENT@reg.Triumf.CA)
3 Oct 1996 20:30:57 GMT
Yousuf Khan (ykhan@achilles.net) sez:
`It seems almost entirely like as if the Earth had no glaciers or cold
`weather of any kind during the age of dinosaurs. Yet in the age of mammals,
`we have glaciers and ice ages (humans came into the Americas because of
`this feature).
`So what happened? Did the Earth start orbiting farther from the sun? Did
`the sun get colder? Why do I now freeze for half the year at a location at
`a latitude that's only 45N (Ottawa, Canada), whereas only a few hundred
`million years ago I could have been working on my tan even at the south or
`north poles?
This is not a question with a simple answer, and I don't think there
is a universally accepted one. what you must understand is that the
global climate system has many feedback mechanisms, and appears to
be capable of inhabiting several different metastable equilibria.
Here are two possible candidates proposed for influencing global
climate: the rise of the Himalayan massif, caused by the impact
of the Indian subcontinent with central asia, created an unprecedented
obstacle to the easterly flow of air around the globe, forcing
temperate air northward over eastern Siberia, thereby bringing
arctic air south; the disruption of the heat pump mechanism of
the deep ocean currents, allowing cold arctic/antarctic water
to spread toward the temperate zones at the ocean surface, thus
cooling the air.
With either of these events, there comes a feedback mechanism
whereby increasing ice increases surface reflectivity, bouncing
radiant solar energy back into space, thereby enhancing the cooling
trend.
You might find more informed discussion in sci.geo.meteorology
and possibly sci.bio.paleontology.
--
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vincent@triumf.ca <== faster % Pete Vincent
vincent@vcn.bc.ca (freenet) % Disclaimer: all I know I
% learned from reading Usenet.
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