Re: Democratic candidates address the issue of global warming while Republicans snooze...

On Thu, 3 Jan 2008 10:24:59 -1000, "Alvin E. Toda" <aet@xxxxxxxx>
wrote:

On Thu, 3 Jan 2008, Islander wrote:

Jean Smith wrote:
In article <0KSdnSrtBYQBU-banZ2dnUVZ_oWdnZ2d@xxxxxxxxxxxxxx>,
Islander <nospam@xxxxxxxxxxx> wrote:

California Poppy wrote:
The issue of global warming may or may not be true. Sadly, the
bad
science in Gore's movie makes it difficult to tell. There have
been
warm times in earth's history as well as ice ages. But, we
dont' know
enough about them to make any certain statements. The idea that
human
activity has caused the current global warming (if it is real)
has not
been proved. Making all of the changes that it implies could
wreck
our economy. So, I favor waiting for scientific proof.
Remember that
in the '70's they were saying we were heading into an ice age.

Who was saying that we were heading into an ice age in the '70s?

Go to the website below to follow links to specific references.

http://www.realclimate.org/index.php?p=94

The global cooling myth

Every now and again, the myth that "we shouldn't believe global
warming predictions now, because in the 1970's they were
predicting an ice age and/or cooling" surfaces. Recently, George
Will mentioned it in his column (see Will-full ignorance) and the
egregious Crichton manages to say "in the 1970's all the climate
scientists believed an ice age was coming" (see Michael
Crichton¹s State of Confusion ). You can find it in various other
places too [here, mildly here, etc]. But its not an argument used
by respectable and knowledgeable skeptics, because it crumbles
under analysis. That doesn't stop it repeatedly cropping up in
newsgroups though.

I should clarify that I'm talking about predictions
in the scientific press. There were some
regrettable things published in the popular press
(e.g. Newsweek; though National Geographic did
better). But we're only responsible for the
scientific press. If you want to look at an
analysis of various papers that mention the
subject, then try
http://www.wmconnolley.org.uk/sci/iceage/.

Can you help with the precession theory of orbital
forcing? Googling other sources contained claims
that said that the northern hemisphere should be
building icesheets and others denying it.

I think you may be referring to theories about the
change in the axis tilt of the earth which gives us
our seasons. Milankovich, a Serbian civil engineer
and mathematician, published pioneering work on this
in 1930, suggesting that the changes in the polar ice
sheets, and possibly ice ages, might be caused by the
wobble of the earth as the axis tilt changes over
major and minor cycles. The changes are slight, from
about 21.5 degrees to about 24.5 degrees and there
are a variety of sub variations within this change.

One of these minor variations is called precession
and is due to the effects of the gravity of the moon
and the sun on a bulge in the Earth's surface at the
equator. There are also smaller effects due to
Jupiter and Saturn. At present this causes southern
hemisphere seasons to be slightly more severe than
northern seasons, assuming no other effects are at
work.

How much this might affect the climate warming that
we are presently seeing is controversial. These
cycles are very long, on the order of thousands of
years, and the effects are small relative to the
major change that we have seen over a relatively
short period of time in increasing CO2 levels.

I have a problem with this theory because while winters
are colder, the tilt also causes the summers to be
warmer. Any long term climate change from this effect
must be secondary in scale.


I agree the effect is not very significant. The
eccentricity of Earth's orbit is one part in 60, so
the difference in luminosity from the sun between
apogee and perigee is 1.016 squared or about
1.032, three percent. More important, I'd say,
though still not very important, is the fact that the
Earth is moving more slowly at aphelion which
occurs in early July, when the Southern
hemisphere is in its winter, so the Southern
hemisphere winters are slightly longer than the
Northern, I guess by the same three percent
since that ratio is also a square. See the cute
moving illustration at:
http://tinyurl.com/2fzt4y


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