We saw recently, didn't we, how contrails help reduce the transparency of the skies, so that they will never again be as blue as they were ~ or we like to think they were ~ during our childhood? Well turns out they increase global warming considerably, that veil they produce serving to trap solar radiation and warming the atmosphere.
They've even got their own interest group at contrails.org where you can order tee-shirts and spray-cans of shaving-foam to create your own trails in the class-room.
But now Google, guardian of this blog, has underwritten a project intended to ask pilots to ascend or to descend so as to stop producing these contrails at all... or at least in one small patch of sky.
They are produced in the first place by a process called sublimation, when the hot gases emerging from jet-engines freezes so quickly that they miss out the bit in the middle we learned about at school called the liquid phase... altogether. Had they not done so, the vapour would simply evaporate rather than form reflective ice-crystals.
All depends though on the temperature of the outside air, and the only way to alter that is to climb or descend into colder or warmer air. Note to pilots, the atmospheric temperature does not continue to fall with height but eventually stays put at the levels Concorde flew at, and rises briefly beyond. Back at space, however, you must not go out without a coat on.
Nonetheless as commercial aviation is set to double in the near future, all of this is about as effective as trying to mitigate global sea-level rise with dessert-spoons and buckets.
Shanwick is a conflation of Prestwick (Scotland) and Shannon (Ireland) and sounds like it should be pronounced without a 'w' but with an 'Ahaaar' at the end of it... but isn't.
