Re: Ice Ages

3 Oct 1996 21:30:40 GMT

pete (VINCENT@reg.Triumf.CA) wrote:
: Yousuf Khan ( 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.

For an interesting discussion of the history of Earth's climate easily
accessible to the layperson, I recommend a book titled "The Time Before
History." Unfortunately, the author's name escapes me. I believe the
book was published in 1994.

One of the factors affecting climate is the presence of greenhouse gases
in the atmosphere, particularly CO2. Apparently recent research has
shown how the raising of the Himalayas by the collision of the Indian and
Asian tectonic plates has likely resulted in the "scrubbing" of large
amounts of CO2 from the atmosphere, thereby increasing heat loss and
lowering global temperatures.

David Wasserman
Curmudgeon-At-Large (
"The older I get, the more value I place on experience."