[NatureNS] The Hockey stick and astronomical cycles

Date: Sun, 26 Nov 2006 12:35:50 -0400
From: David & Alison Webster <dwebster@glinx.com>
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These cycles will have effec


Patrick Kelly wrote:

>
> The astronomical cycles that David refers to are called Milankovitch 
> Cycles.
>
> http://www.ncdc.noaa.gov/paleo/milankovitch.html
> http://en.wikipedia.org/wiki/Milankovitch_cycles
>
Hi Patrick & All, Nov 26, 2006
Thanks for these URLs. The top one led me to
http://www.aip.org/history/climate/cycles.htm#M_52_
which contains a good account (or so it seems to me) of climatology over 
the years.

One passage in this account has me baffled and perhaps someone can 
explain. The passage being "The changes in the atmosphere could also 
answer the old persuasive objection to Milankovitch's theory -- if the 
timing of ice ages was set by variations in the sunlight falling on a 
given hemisphere, why didn't the Southern Hemisphere get warmer as the 
Northern Hemisphere cooled, and vice-versa? The answer was that changes 
in atmospheric CO2 and methane physically linked the two hemispheres, 
warming or cooling the planet as a whole.(52*) "

What configuration of tilt and orbital distortion could lead to one 
hemisphere receiving more insolation in e.g. summer than the other 
hemisphere would receive 6 months later ? Tilt would have to be 
symmetrical and even if the sun was at times not exactly at the 
intersection of the major and minor axis of the orbital ellipse, surely 
this assymetry would not flip in the space of 6 months.

Yours truly, Dave Webster, Kentville




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