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My understanding is that these long cycles in global climate have been taken into account in the current climate models, and that they do not account for the intensity of the current cycle.
Mark Shapiro
-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu on behalf of Shapiro, Mark
Sent: Mon 8/20/2007 12:16 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Still More Global Warming
See http://en.wikipedia.org/wiki/Milankovitch_cycles for information about the long-period climate cycles.
Mark
-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu on behalf of John Mallinckrodt
Sent: Mon 8/20/2007 11:41 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Still More Global Warming
Jim Green wrote:
I am still trying to understand Global Warming -- and the topic just
seems not to go away -- even Gore on Oprah for Pete's sake.
Do I understand correctly? -- sort of?:
Every 23kyr or so the Earth warms up -- and some 12kyr later it
freezes.
Not according to the evidence. See, for instance, <http:// en.wikipedia.org/wiki/Global_warming>
Ocean level varies some 30m in the process.
Well, more like 100 m and mostly in the downward direction (when all the water gets piled in solid form on top of the polar regions.) See, for instance, <http://en.wikipedia.org/wiki/Sea_level_rise>.
It's interesting to note that ocean levels are very rarely as high as they are today and that we seem currently to be in a multi-thousand year period of rare stability. My own not very well fleshed out pet theory is that this rare stability may be something of a prerequisite for the rise of civilization, e.g., you need to be able to establish and depend on ports.
The people in Florida don't much like this; the people in Canada are delighted when
it gets warmer.
Depends on what "this" is!
... But why 23kyrs? Well that is the period of the Earth's precession.
Wrong question => wrong answer. See above.
But why does the precession change the Earth's average
temperature? Yes, the tilt tinkers with weather patterns, but the
cross section toward the Sun doesn't change.
A bit of tutoring would be appreciated.
Bottom line: It's really complicated and not very well understood. I think the best advice is to read up on it yourself and come to your own conclusions. There is no dearth of material available online.
John Mallinckrodt
Cal Poly Pomona
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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
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