On Feb 27, 7:14 pm, (Doug Miller) wrote:
In article , Chris Friesen wrote:
Doug Miller wrote:

The problem with that notion is the assumption that we *can* do something
about it. Suppose, for example, that global warming is real and is due
*entirely* to increased solar output. What are we going to do, install a
dimmer switch on the sun?

Actually, it's not totally out of the question. Theoretically you could
put one or more large mirrors between the earth and the sun and maybe
even use the reflected light for a power-generation plant.

Yes, I'm familiar with the idea. But if it was practical... it woulda been
done already.


While it is not practical to put a giant venetian blind
in orbit to block sunlight before it reaches the atmosphere
it IS possible to put particulates into the upper atmosphere
to reflect sunlight away. Indeed we have been doing exactly
that with jetliner contrails.

The contrails are formed of ice crystals which, unlike
water vapor, contribute little to the greenhouse effect,
but do add significantly to albedo. The estimate is
that in the last 50 years energy reaching the surface
of the Earth has decreased by a net 2%. That is
way more than enough to offset the effect of any
increase in the solar constant even if we assume
the highest credible estimate of 0.1 W/sqm.

The reality of global dimming is obvious if you look
at a satellite photo of a 'clear' sky. Over much of
the world today, the sky is NEVER clear.

Were global dimming the only factor affecting climate
change we should have noticed a drop in temperature
over the last 50 years. That we have not, is particularly
ominous.

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FF