Re: Global warming deniers


Puppet_Sock wrote:
Robert Grumbine wrote:
In article <1146694711.026435.156860@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Puppet_Sock <puppet_sock@xxxxxxxxxxx> wrote:


Well, that was sort of my question.

The graph of solar irradiance in that page has oscillations
of about 1W/m^2. The forcing function is taken to be
about 1/6 or less of the change. Why? Something is
going on here.

Indeed. Two things, both of which are taught in elementary
meteorology courses:
1) The earth is a sphere, not a disk.
2) The earth reflects some of the incoming solar radiation

The 1 W/m^2 is the observed change in the solar output over a
solar cycle -- as received by a plane perpendicular to the sun's
rays, at a distance of 1 Astronomical Unit (AU).

If the earth were a disk squarely facing the sun, and we cared
only about the sunlit side, the area intercepting solar radiation
would be pi * r^2. But the earth is, in fact, a sphere(-oid), whose
area is 4*pi*r^2. A change to the disk of 1 W/m^2 is equivalent
to a change of 0.25 W/m^2 averaged over the surface of the sphere.

The earth's albedo (portion of solar radiation reflected back
out of the system) is about 0.3. 30% of those 0.25 W/m^2 are
immediately bounced out and never have a chance to affect earth's
climate.

That leaves about 0.17 W/m^2 to participate in earth's climate,
or about 1/6th of the solar variation -- as measured by solar people
above the atmosphere on planes perpendicular to the sun and referenced
to 1 AU.

Actually, 0.25 * 0.3 is 0.075. You think you dropped a digit some
place?
I love it when people talk down to me about numbers.


Allow me to oblige you then.

If the Earth albedo is 30% then the non reflected portion is 1 - .3 or
..7
and 0.7 * 0.25 W/m^2 is ~ .1.7 W/m^2.

Hope you enjoyed it as much as I did.

.

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