From James Cater
Your article on contrails from aircraft implies that these long trails of water vapour and ice increase global warming because they encourage the development of cirrus clouds, which in turn reflect large amounts of heat radiated by the Earth, heating the atmosphere (19 October, p 6). So aircraft should fly lower to prevent cirrus clouds forming.
But the following week, your article on cirrus clouds implies that when there are less cirrus clouds (as happened after 11 September when aircraft were grounded), more sunlight comes in, causing the daily temperature variation in the US to grow by up to 3 °C (26 October, p 51). So do cirrus clouds (especially those formed by contrails) increase global warming or not?
Dunstable, Bedfordshire, UK
