This is an interesting question . Roy Spencer looks like a
reasonable guy and I'd like to email him when I have time .
Solar heating raises the temperature of continents more than water
because the heat capacity of land is lower. Bill Patzert, an
oceanographer at NASA's Jet Propulsion Laboratory explains: "The
temperature of land changes easily, which is what we mean by low
heat capacity. Consider the desert: At night the desert is cold,
perhaps only 60o F (16o C). When the Sun rises in the morning the
temperature might jump to 100o F (38o C) or more." Such mercurial
behavior is characteristic of materials like rocks and soil with
little thermal inertia. It doesn't take much sunlight to
substantially elevate their temperature.
is exactly what I would expect : greater variance over land than
ocean which , as they say has enormous heat capacity. ( It reminds
me of the one question I missed on a highschool chem quiz which
caused me to not have the highest grade in the class : What common
substance has the highest specific heat ? Having spent hours browsing
my CRC Handbook of Chemistry and Physics , I naturally said hydrogen .
The answer was water . The instructor would not accept H2 saying it
wasn't common . Still pisses me off . )
Anyway , just on the basis of the difference in heat capacity , I don't
understand why the mean would change , unless they are talking daytime
Note the 2.3c [ .8% ] variation is greater than the entire worst case
prediction for the next century of about 0.2c or .07% ( .0007 )
per decade .
[ From the fundamental equation for the earth/sun temperature relationship ,
the total seasonal effect of the asymmetry is actually about 2.3% ,
hugely greater than the supposed "greenhouse" effects . | 060702 ]
While this is a bigger variation than I would off hand have expected,
the variation may be due to the second order effect which came to
light in the discussion with Perry Metzger on the Junto list . If there
is an asymmetry in the albedo between the side of the sun facing
the sun and that facing elsewhere - as Perry calculated for disks
which a dark side facing the sun and a white side facing away ,
and visa versa - the mean temperature of the object will depend
on the ratios of refectivities of the two sides. I pointed out that
while the rotation of the earth eliminated the earth having any
particular "sides" , changes in albedo of the poles or the
insulative properties of the atmosphere over them ) would
change mean temperature .
I didn't consider the 23.5 degree ( 47 between tropics ) tilt of the axis
and the asymmetry of the albedo of the northern land masses versus
Antarctica and its surrounding oceans . In any case those effects
must factor in to any explanation of the variation.
Too bad I'm not a professor of something somewhere so I'd have an
income to explore all this stuff in detail . To bad I don't have an income
for any of the stuff I do .
Peace thru freedom ,
I forwarded your "Global Warming" webpage to a mailing list I'm on,
and a friend asks:
Can Bob Armstrong explain why the mean temperature of the Earth
is 2.3K higher in July when we're furthest from the sun?
I asked him for the source of that data point, and he responded: