Fwd: Climate change (was RE: Op-Ed LA Times: Oil decline)

Meant to send this to the list.

Joel

>Date: Tue, 17 Feb 2004 11:58:29 -0500
>To: "Glenn Morton" <glennmorton@entouch.net>
>From: Joel Moore <joelmoore@psu.edu>
>Subject: Climate change (was RE: Op-Ed LA Times: Oil decline)
>Cc:
>Bcc:
>X-Attachments:
>
>On the topic of climate change, it seems that abrupt climate change
>is becoming more worrisome than a runaway greenhouse. The earth is
>now in a more regular glacial-interglacial cycle than the times
>mentioned below (with perhaps the exception of the Miocene). So
>rather than a runaway greenhouse, the concern is that a switch will
>be tripped that will cause the onset of an ice age. In short, the
>idea is that quicker melting of the ice sheets increases the
>freshwater flux into the North Atlantic. Greater amounts of
>freshwater will dilute the cold, saline water that currently sinks
>in the North Atlantic. Once the cold, saline water is sufficiently
>diluted and stops sinking, the Gulf Stream shuts down and
>temperatures plunge, particularly in Europe.
>
>For more details on political effects and a very general description
>of the science see Fortune magazine's recent coverage of a report
>from a Pentagon think tank about possible effects of abrupt climate
>change.
>http://www.fortune.com/fortune/technology/articles/0,15114,582584,00.html
>
>
>I chatted with a geology prof here at Penn State about it. He said
>that the report paints the worst case scenario but that looking at
>that scenario is probably a good balance to those who stick their
>heads in the sand and say that there's no chance that humans are
>affecting climate. In talking to politicians, he's said that of
>course the scientific scenarios aren't 100% certain, but politicians
>make policy decisions all the time on the basis of economic
>projections, which are based on a lot less evidence and are less
>certain than scientific projections (because after all economic
>projections are dealing with people rather than physical
>interactions).
>
>A few more details on the background: The detailed paleoclimate
>records that are much of the basis for the Pentagon report could
>only have come from polar ice-core records. These records show
>sudden shifts such as the warming at the end of the Younger Dryas
>(~11,500 years ago) where the temperature warmed 10-15 degrees C in
>10-20 years. The most plausible explanation for such sudden jumps of
>climate is start up and shut down of the Gulf stream/North Atlantic
>Ocean circulation as mentioned above. While, it seems as though the
>descents into colder regimes usually take longer, but human-induced
>change may trip a switch and make that process happen much quicker.
>
>Joel
>
>>Speaking of the greenhouse effect one should keep things in historical
>>perspective
>>
>>Today the earth has about 400 ppm. Below are the ppms for CO2 for ancient
>>periods.
>>
>>
>> P(CO2)
>>Miocene Pakistan <700
>>Miocene E. Africa <400
>>Eocene Wyoming <600
>>L. Cretaceous Texas 2500-3300
>> Spain 1600-2600
>>U. Triassic/
>>l. Jurassic New Haven 2000-3000
>> New Haven 2500-4200
>> Fundy Rift 3000-6000
>>Thure E. Cerling, "Carbon Dioxide in the Atmosphere: Evidence from Cenozoic
>>and
>>Mesozoic Paleosols," American Journal of Science, 291(1991):377-400, p. 394
>>
>>It is true, that the sun was weaker in the past than today so we don't want
>>to go back to 6000 ppm, but everyone freaking out about going from 300-400
>>ppm in my lifetime is a bit over the top. That rate of increase can not and
>>will not be sustained long enough to put the earth into runaway greenhouse.
>
>
>--
>
>Joel Moore
>315 Hosler Building
>Department of Geosciences
>Pennsylvania State University
>University Park, PA 16802
>
>(814) 863-8055
>http://www.geosc.psu.edu/~jmoore/

-- 
Joel Moore
315 Hosler Building
Department of Geosciences
Pennsylvania State University
University Park, PA 16802
(814) 863-8055
http://www.geosc.psu.edu/~jmoore/