On 28/06/2010 14:43, Scott W wrote:
I've watched a perfectly blue sky this morning slowly deteriorate into
a mess of criss-cross contrails / chemtrails, haze and cirrus.

They are contrails. Even the moronic Daily Mail admits that!
Ignore the halfwitted delusional US nutters chemtrail claims.

Could someone enlighten me as to the genuine reason behind this - I
always thought it was down to water vapour condensing from jet engines
- but as I look up some of these contrails stop and start. The old
fashioned contrails were just continuous lines across the sky.

If the air is borderline for cloud formation or super saturated but with
insufficient nuclei to initiate condensation then the con trail will be
very strong as the soot in the exhaust and extra water vapour condenses
as ice and tips the balance in favour of cloud formation.

A nice strong crosswise wind will make them look very pretty indeed
giving a patch of rectangular cirrus after a while. Gaps occur where the
air is not ready to form clouds and the contrail quickly dissipates as
the ice sublimes in the sunlight faster than new water vapour condenses.
Then you see a short stubby con tail behind the aircraft.

It has been suggested that during the volcanic flight ban the skies
were far bluer than usual - but I thought this was down to a very
clean, dry airstream from the north-west.

It was a clean northerly airflow. Although when there really was ash as
well you could see a lot of white scattering around the sun and very red
sunsets.

Further suggestions as to the reason are explained in this Daily Wail
article which includes a theory that these chemtrails consist of
chemicals that calm the population down?

http://www.dailymail.co.uk/sciencete...-sunshine.html

Even the Daily Wail doesn't take chemtrails seriously. They are only
mentioned in the discussion by a handful of American nutters - the sort
who also believe 9/11 used explosives and was done by the Illuminati.

Regards,
Martin Brown