ABSTRACT
The obvious visible effect that aviation has on the atmosphere is the wellknown contrail (condensation trail), first described by meteorologists in work dating back to the 1940s and 1950s by Schmidt (1941), Appleman (1953) and Brewer (1999). Contrails are line-shaped ice crystal clouds formed behind aircraft from the initial emission of water vapour and particles from the engines, which is caught up in the wing-tip vortices into a cold, ice-supersaturated atmosphere. The epigraph above was not from a recent commentator on the effects of aviation on climate, but rather Dr Walter Orr Roberts, the then Director of the National Center for Atmospheric Research in Boulder, in a newspaper interview in The New York Times, 23 September 1963.
