[Coral-List] AGW, solar activity, etc

[David M. Lawrence]

I can't say I quite understand the galactic rays concept -- it seems 
rather odd to blame passages through spiral arms of the galaxy about 
every 140 million years to climate changes that have a much higher 
frequency -- on the scale of thousands of years.

It's also odd to posit that the solar system passes through patches of 
energy waiting to screw up the climate, or that such passages have 
happened frequently enough to affect climate on time scales of interest 
to us.

Proximity to a source of radiation is key -- and as energy spreads out 
in all directions from the source -- it seems it would take some fairly 
fancy mathematical sleight-of-hand to make the hypothesis work.

If we passed close enough to another source of radiation to affect our 
climate, we would likely have more serious problems, like the gravity of 
the other object hurling planetoids hurled out of orbit and toward us 
for a rather unpleasant impact.  (The hypothesized Nemesis comes to mind.)

I ran some radiation calculations which would seem to cast further doubt 
on the galactic rays hypothesis.  I calculated the energy flux reaching 
us from the two main stars of the alpha Centauri system (our closest 
neighbors at 4.4 light years away).  I get 3.65x10-8 W m-2 (0.0000000365 
W m-2).  When added to the energy coming from the sun, this produces a 
temperature increase of 2x10-9 degrees (K or C). To get the full effect 
of this negligible influence, that is 0.000000002 of a degree C or K.

Even if we were talking about cosmic ray effects on clouds, I would be 
VERY skeptical that this hypothesis holds any water.

Dave

Jeremy Kemp wrote:
> If galactic rays
> is what you’re referring to on the other issue, that is also extremely
> questionable, pretty much to the point of being discredited. The original work
> (primarily by Friis-Christensen &
> Lassen, and Svensmark) has been well critiqued by, for example, Benestad, and Damon & Laut. Their work has not, to my knowledge, been convincingly
> critiqued in return. Similarly to solar output, galactic rays are an ‘issue’
> regularly used by so-called skeptics to muddy the waters.

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