On Dec 27, 3:32*pm, "Tim Ward" wrote:
"Martin Gregorie" wrote in message

...



On Wed, 23 Dec 2009 13:13:54 -0800, Newill wrote:

On Dec 23, 10:38 am, Martin Gregorie
wrote:
On Tue, 22 Dec 2009 22:21:46 -0800, Frank Whiteley wrote:

Note my comments to the article about soaring near Oxford when the
persistent contrails filled the southern sky.

Yes, and I remember the discussion on r.a.s about contrails and their
spread-out to form cirrus just after the post-9/11 three day warm
period was reported. IIRC the discussion then was about the effect of
contrails in the soaring areas beneath flight paths out of large US
West Coast airports.

--

In the USA there was a rather well done program on NOVA or Frontline
(PBS) that investigated the impact of the contrails and concluded that
contrails actually contribute to global cooling - not warming!

So, how did they explain the 1 degree C rise in ground temperature during
the three days when all civil aviation was grounded?

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

I think they explained it this way:
If the temperature rises when the clouds are _not_ there, then, logically,
it's possible that *the presence of the clouds makes it cooler.

Tim Ward

Clouds cool in the day by reflecting sunlight back into space and keep
the warmth in at night so minimum temps are warmer than on clear
nights.