Re: [Phys-l] Still More Global Warming

[marx@phy.ilstu.edu]

Hi All:
	For an interesting historic perspective on the Earth's climate, please refer to
http://www.scotese.com/climate.htm

Note on the first page the history of the Earth's temperatures.
This is similar to what Jim Green was referring.



On 20 Aug 2007 at 11:44, JMGreen 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.  Ocean level varies some 30m in the process.  The people in 
> Florida don't much like this; the people in Canada are delighted when 
> it gets warmer.
>
> Sometimes people make a mess of the atmosphere -- worse in some 
> places -- eg in LA and Bejing (sp?)
>
> We need some green house gasses to keep tolerably warn -- nuclear 
> reactions in the core don't suffice.
>
> But why 23kyrs?  Well that is the period of the Earth's precession.
>
> 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.
>
> Jim
>
> J M Green
> Email:  MailTo:JMGreen@sisna.com
> WWW: HTTP://users.sisna.com/JMGreen
>
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