The warming effects of aircraft are much greater when they fly in the night than when they fly during day time, according to a study that says a ban on night flights could reduce the warming effect on the climate.

Piers Forster, an environmental scientist at the University of Leeds, and other researchers studied flights crossing Britain at night, not takeoffs and landings from its airports.

The scientists monitored air traffic over Britain and worked out that, although one in four flights occurred between 6 p.m. and 6 a.m., they contributed 60-80 percent of the warming that could be attributed to contrails, reported the online edition of The Guardian.

Winter flights had more effect than those in the summer, contributing 50 percent of the warming despite providing only 22 percent of traffic.

"Night flights are twice as bad for the environment. If the government wants to reduce the likely impact of aviation on climate then it could ensure that more flew during the day," Forster said in the journal Nature.

Aircraft contrails enhance the greenhouse effect because they trap heat in the same way as clouds. During the day, their warming effect is not as pronounced because contrails reflect sunlight back into space, which helps to keep the planet cool.

This means contrails are responsible for about half of the aviation industry's impact on climate, Forster said.

"Aircraft currently only have a small effect on climate. However, the fact that the volume of air traffic is set to grow rapidly in coming years makes it important to investigate the effects of contrails on our climate."

Shifting all night flights in Britain to the daytime would save the equivalent of 2.5 percent of the country's annual carbon dioxide emissions, he said.