Attached Link: http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_qa.shtml

danamo - sounds like tests to measure the global dimming effects of contrails? Here's another link, connected to the BBC TV series. Ashamed to admit that I stopped watching it 'cos it got too scary. Not much point in having all that information if there's nothing you can do with it :^(