Wednesday, 22 October 2008

He that regardeth the clouds shall not reap...

Ecclesiastes, 11:4 (...he can just lie around)

As Member Number 8158 of the 13,580 members (in 66 countries) of the Cloud Appreciation Society I note that the Society's current newsletter features this as Cloud of the Month for October; there is a better picture of it here.

What it shows, of course, are not exactly clouds, they are contrails; these are the long lines of cloud that form behind high-altitude aircraft, and can make a latticework of the sky. Are they a cloud type that we in the Cloud Appreciation Society should appreciate ? The society is polling its members to see whether they feel we should. At the moment the voting is 65% in favour, 35% against (there are no Don't Knows; we in the CAS do not equivocate).

The argument for appreciating them are:
They can serve as early indicators of a change in the weather, for when contrails persist and spread across an otherwise blue sky, they can be the first sign of the arrival of a weather front, which will eventually bring rain. Also they can be very beautiful. When the conditions are right for contrails to persist in the air, they overlap, bisect and spread in the high-speed winds at cruising altitude, adding a modernist counterpoint to the chaotic, impressionistic formations of the natural clouds.

...and against:
The water vapour element of aircraft exhaust may not be the most significant from the point of view of climate change but it is the most visible expression of the effect that aviation is having on our atmosphere. Contrails also encourage the formation of other high clouds, like Cirrus and Cirrostratus, which tend to trap in the Earth’s warmth, rather than reflect away the Sun’s heat like low clouds. This only affects ground temperatures while the clouds are in the sky, but the ever-increasing amount of air travel means the overall warming effects caused by contrails might well be significant.

There might just be a possibility of reversing global warming by increasing the whiteness of clouds over the world's oceans. A report by scientists at the universities of Edinburgh, UK, and Boulder, Colorado, US, has been published in the journal of the Royal Society; it proposes the use of automated ships to spray sea salt up into the clouds. This should encourage the clouds to form more droplets and reflect away more of the sun's heat.

If this happens—and actually works— the CAS will soon be receiving membership applications from Gordon Brown, Barack Obama, Nicolas Sarkozy, and other grateful world leaders. They will have to pay the four pounds plus postage membership fee, just like everyone else.

You can join here, or just go there and look at some lovely pictures.

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