contrails

On Dec 23, 6:44*pm, Martin Gregorie
wrote:
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 * * * |

The daily maximum temperature did rise the 3-day hiatus which any
meteorologist would have expected. The size of that rise was much
larger than anyone expected. The reason is that high altitude jets
leave contrails that are sometimes nearly invisible but still reflect
substantial solar energy back into space. At night, the same
contrails reflect heat back to the earth resulting in warmer daily
minimum temperatures. The days got hotter and the nights got colder.
Contrails tend to dissipate during the day so the net effect is
warming. This complexity is typical of the climate debate.

Climate change 'skeptics' are throwing the word "temperature" around
without really knowing what it means. For example, just what
temperature are we talking about? Minimums, maximums or just the
average. For that matter, exactly how is temperature measured? Just
walking outside with a thermometer won't do it. Finally, what are you
actually measuring?

The World Meteorological Organization (WMO) publishes an extensive
manual on how to measure surface temperature. It specifies standard
equipment and methods. It's not easy to do.

The effects of global warming are also different from what most
people expect. Currently, the largest effects are on minimum
temperatures in northern latitudes. Even if daily maximums don't
increase noticeably, warmer daily minimums are having substantial
effects - particularly on ice.