On some otherwise cloudless days, the sky over England is criss-crossed with contrails from high-flying aircraft. These are a rapid accelerator of climate change.
Contrails may last only half a day but they cause as much global heating in that time as the carbon dioxide released on the entire flight, although this exhaust gas will survive in the atmosphere for 100 years.
This startling fact came up in a general discussion about how to cut emissions from aviation with new fuels, hydrogen, biofuels and electric engines.
None of these possible solutions will be developed quickly and all will be more expensive than existing technology, but the Whittle Laboratory in Cambridge believes that reducing contrails on the routes in the northern hemisphere with the heaviest traffic would have an immediate beneficial impact.
Although contrails are common, their formation largely depends on the atmospheric conditions. At different times on different days, flights may produce long-lasting cloud formations or none.
With aircraft travelling so fast, it is impossible for pilots to see the contrails far behind. Flying at lower heights would slightly increase fuel costs but massively reduce contrails.
Scientists are trying to find a workable solution to help governments eliminate the familiar white lines across our skies that are so rapidly warming the planet.
