In a bizarre illustration of the actual impact jet trails have on temperature, scientists in England say that the grounding of planes across Europe could have an immediate and measurable impact over the continent in the next few days.

The Daily Mail report that, in 2002, a team from the University of Wisconsin-Whitewater, studied temperature change after all flights were grounded in the wake (triple-meaning pun!) of 9/11. They found that "the difference in daily high and nightly low temperatures in the absence of planes' contrails was more than 1c greater." Because, report the Mail, "in regions with crowded skies, the clouds formed by the planes' water vapour worked like cirrus clouds to prevent days from getting too hot and trapping the Earth's heat at night."

Air traffic across Europe has now been grounded for 48 hours in the wake of a volcanic eruption in Iceland. Meteorologists expect a similar effect. Although some caution that the ash the eruption has spewed into the atmosphere could counter the change.