From: ct (tilley@att.net)
Date: Fri Jul 20 2001 - 08:02:02 MDT
From: "Robin Hanson" <rhanson@gmu.edu>
> Wow. An extropian complaining that an elaborate analysis of the
future
> just still isn't detailed enough to inform our choices. :-) ...
> ...My attitude is to draw tentative conclusions
> from whatever is the best analysis in an area.
(Seems your attitude attepmted divergence during the SETI/ASTRO
discussion/analysis<g>!
> No, a more complex model can *validate* a simpler one...
> ...I don't have to always use the
> most complex possible model.
.
.
.
> Yes, as usual the effective way to challenge one model is with
> another model.
Not according to Anders...but, whatever.
=============================================
More fodder for the debate:
http://www.ucar.edu/communications/newsreleases/2001/temps.html
Earth Likely to Warm 4-7 Degrees by 2100
New estimates of sulfur dioxide and other emissions, along with updated
information on carbon storage, ocean circulation, radiation, and other
components of the earth system have improved computer models of the
earth's
climate and led the IPCC to both raise and widen its estimated range of
global temperature increase. The latest range of 2.5-10.4 degree F is up
significantly from the panel's 1995 estimates of 1.4-6.3 degree.
In their analysis Wigley and Raper attempted to interpret the likelihood
of
the new estimates, taking into account the wide uncertainties about
future
human activities and the climate's response to them. They identified the
main sources of uncertainty and estimated the probability of their
values
falling within defined ranges. They then used these results to "drive" a
simplified climate model and combined the various model results into
probability ranges for temperature increases
=============================================
http://www.eurekalert.org/pub_releases/2001-07/uow-wld071001.php
World land database charts a troubling course
AMSTERDAM -- Over the past 300 years, in an ever-accelerating process,
humans have reshaped the terrestrial surface of the Earth. In doing so,
humanity has scripted a scenario of global environmental change with
impacts
that promise to be at least as severe as global climate change,
scientists
reported here today, July 11
=============================================
FWD: 16Jul01 Eurekalert
Arizona State University College of Liberal Arts & Sciences
Watch global warming happen in real time - on Mars
Though there has been a fair amount of evidence that the Earth's
atmosphere
is undergoing global warming, the process is slow enough that there are
plenty of skeptics, including some very influential people, who argue
that
it may not be happening at all.
Global climate change does occur, however, and sometimes so quickly that
you
can watch it happening. Just look at our neighbor, Mars: within the last
month, the global atmospheric temperature of Mars has increased by
approximately 50 degrees Fahrenheit, according to data being received by
the
Thermal Emission Spectrometer (TES) on NASA's Mars Global Surveyor
spacecraft.
The cause of this sudden shift is a giant dust storm that has snowballed
and
now has enveloped almost the entire planet, absorbing a lot of the Sun's
energy in the upper atmosphere.
"It started out as a large dust storm in the southern latitudes in late
June," said Arizona State University's Korrick Professor of Geology
Philip
Christensen, the principal investigator for TES. "The dust trapped
sunlight
and heated the atmosphere locally. As this warm air flowed to regions
where
the air was still cool it generated winds which raised more dust into
the
atmosphere.
"By the end of the first week in July, most of the planet was enveloped
and
our readings of atmospheric temperature had increased by about 30
degrees
Centigrade."
TES is an instrument designed to take detailed readings of energy
emissions
in the infrared range (heat energy) to aid in studying Mars' geology and
atmosphere. A movie showing the instrument's readings over the last
month,
tracking the expanding dust storm and the accompanying increase in
atmospheric temperature, is available on the web at:
http://tes.la.asu.edu.
Curiously, just as Earth's global warming may theoretically cause the
opposite thermal effect on some parts of the planet, so Mars' current
heat
wave is likely to bring on a big chill further on down the road.
"In the end, the cloaking of the entire planet with dust is probably
going
to cool down the surface of Mars significantly and ultimately shut this
entire weather system down again," said Christensen. "It's kind of like
what
we imagine would happen with a nuclear winter on Earth." In fact,
Christensen points out, it was another global dust storm observed on
Mars in
the early 1970's that gave astronomer Carl Sagan and others the idea of
the
kind of catastrophic climate change that might be caused by a global
nuclear
war.
"Mars' atmosphere is a much simpler system than Earth's," Christensen
cautions, "since it is much thinner and lacks most of the water that we
have
in ours, trapping energy and moderating changes. "Still, it provides us
with
an interesting model for how global climate changes can occur, albeit
much
more quickly than on our planet. Nonetheless, some large scale changes
here
could be abrupt as well."
=============================================
ciao/ct
This archive was generated by hypermail 2.1.5 : Sat Nov 02 2002 - 08:09:06 MST