[ATMoB-discuss] Contrails

[Glenn M]

I recently saw an interesting and timely NOVA program (aren't they all?) -
"Dimming the Sun" http://www.pbs.org/wgbh/nova/sun/about.html which looked
at (among other things) the sharp rise in average surface temperatures
immediately after Sept 11, 2001, when all aviation ceased over most of the
world for several days.  (I'm sure many of you also noticed how incredibly
clear the skies were in the week or so that followed that tragic day.)  

Short version:  A weather researcher also noticed this and happened to be
the guy calculating these temperature averages.  He observed a sharp,
immediate temperature rise that stayed up until well after air travel
resumed.  He worked to understand why the temperature shot up abruptly and
did a pretty good job of tying it to the -lack- of contrails.  The
contrails, he says, result in a 10% - 18% attenuation of sunlight around the
world, the amount depending on where you are.  See also:
http://www.pbs.org/wgbh/nova/sun/contrail.html .  He also tied his
observation to some other folk's work on evaporation rates (Harvard, and
someone from Germany - sorry, the names escape me), which were observed to
go up immediately following Sept. 11th and are known to track insolation. 

Of course, this  all raises questions with the global warming hypothesis,
and the show concludes with the question of the relative scales of these two
opposing climatic forces.  If this cooling effect is really there, caused by
contrails blocking/reflecting 10-18% of the sun's rays, then the global
warming rate is greater than previously thought, and being partially offset
by this cooling effect.  Stop or reduce air travel and the global
temperature rise would accelerate.  (I'm not one to panic, but find this all
a bit unsettling.)

I highly recommend seeing the show if you can.  I'd be interested to hear
anyone else's thoughts on it.

...gm





-----Original Message-----
From: atmob-discuss-bounces at atmob.org
[mailto:atmob-discuss-bounces at atmob.org] On Behalf Of David Aucoin
Sent: Thursday, May 18, 2006 7:49 PM
To: atmob-discuss at atmob.org
Subject: [ATMoB-discuss] Contrails


As I was looking at the western sky, not moments ago, I noticed no fewer
than 8 plane contrails in the sky. I read somewhere about the amount of
contrails in the sky and how they afect the viewing of the night sky.

Does anyone agree? _______________________________________________
ATMoB-discuss mailing list
ATMoB-discuss at atmob.org
http://lists.atmob.org/mailman/listinfo/atmob-discuss