Recent German scientific research by Ulrike Burkhardt and Bernd Karcher from the DLR Institute for Atmospheric Physics published on 29 March 2011 by the prestigious journal Nature suggests that contrails formed by airliners flying at high altitude may be as significant a contributor to climate change as aviation emissions. The journal has also published a news report written by Olivier Boucher from the UK Met Office Hadley Centre explaining the results.
The potential implications for the airline industry are far reaching, particularly if airliners are forced in future to fly at less fuel-efficient altitudes. To date the focus has been on reducing CO2 and other emissions from aircraft so there has been an alignment of interests between airline companies seeking to reduce their fuel bills and environmental concerns.
For those who want to see under what conditions contrails form there is a neat application available on the web.