Re: OT: interesting global warming quote found elsewhwere

Jonathan Kirwan wrote:
On Mon, 21 Jul 2008 23:54:55 -0500, Kris Krieger <me@xxxxxxxxxx>
wrote:

I know about precession in the earth's orbit, but actually, I don't
knowwhere we are at this moment, i.e. whether the ploe is tilted more
towards the sun, or more away from it.

Um. That's a problem that you don't know. The pole tilts towards and
away from the sun, every year, just at opposite halves of that period.
So that has nothing much to do with polar ice cap melting and so on.

The precessional and faster nutation terms represent gradual changes in the direction of the Earths spin axis. The Earths orbital elements evolve slowly with time with periodic terms driven mostly by the moon but also by the other planets. The best short introduction to the these effects is online at:

http://www.hartrao.ac.za/nccsdoc/slalib/sun67.htx/node203.html

To get yourself up a little bit on the curve of understanding the
orbital Milankovitch cycles, there is a paper by Berger from 1988,
which included the newer numerical integration of the secular
equations (suggested by Laskar in 1986, I think.) It is available at:

http://www.agu.org/journals/rg/v026/i004/RG026i004p00624/RG026i004p00624.pdf

Look at figure 28, page 649.

I think the TAR included a nice graph paralleling the Vostok ice core
data with the Milankovitch cycles, but I haven't looked for a repeated
version of it in the AR4. It's easier on the eye than the above
Berger graph and ties into some other real-world data to help you see
the natural cycles. If I find it and think about it, I'll post a link
to that, too.

http://www.nature.com/nature/journal/v329/n6138/abs/329414a0.html

But you need a subscription to view online.
A bit dated but free access is:

http://adsabs.harvard.edu/full/1989LIACo..28..385R

According to Berger's data above, though, you should be able to see
that we are a little bit on the downward slope of millennial-scale
insolation. You can see a bit of what's up ahead and a lot of what is
in the past.

There are data sets going back many tens of millions of years and
going forward for a similar period, now. If you get to that point, I
can provide a link or two.

There is also some newer work that suggests that some of the short term periodicities seen in climate may also be due to the influence of the moon on our orbital elements. Essentially the hypothesis is that when the elements are just right the enhanced tidal effects cause more mixing in the oceans (and obviously higher tidal range). The models to predict these are very good and well tested to avoid coastal flooding.

The work by Keeling on climate and tides and their possible relation to evolving orbital elements of the Earth moon system is interesting. It is only one of several possible contenders but interesting non the less.

http://www.pnas.org/content/94/16/8321.full.pdf+html

Regards,
Martin Brown
** Posted from http://www.teranews.com **
.

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