The warming effects of aircraft vapor trails could be eased with fewer night flights, especially during winter, the report says.

Sourced through Scoop.it from: news.nationalgeographic.com

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Nicola Stuber, first author of the study, to be published in tomorrow’s edition of the journal Nature, suggests that contrails’ overall impact on climate change is similar in scope to that of aircrafts’ carbon dioxide (CO2) emissions over a hundred-year period.

Aircraft are believed to be responsible for 2 to 3 percent of human CO2 emissions. Like other high, thin clouds, contrails reflect sunlight back into space and cool the planet.

However, they also trap energy in Earth’s atmosphere and boost the warming effect, the study says. […]

Contrails are artificial clouds that form around the tiny aerosol particles in airplane exhaust.

They appear only in moist, very cold (less than 40ºF/4ºC) air—usually at altitudes of 5 miles (8 kilometers) or higher.

Some contrails can last for a day or longer, though they gradually disperse and begin to resemble natural clouds.

Contrails Mystery Scientists disagree about the extent of contrails’ climate impact.

“The jury is out on the impact of contrails,” said Patrick Minnis, an atmospheric scientist at NASA’s Langley Research Center in Langley, Virginia.

David Travis, a climatologist at the University of Wisconsin-Whitewater, notes that some recent studies suggest that contrails have little impact on global climate change but have a greater regional warming impact.

“I prefer to think of contrails as a regional-scale climate problem, as they are most common in certain regions of the world, such as western Europe, eastern and central U.S., and parts of eastern Asia,” he said.

“This is due to a combination of dense air traffic in these areas and favorable atmospheric conditions to support contrail persistence once they form.”

Because of their locations and short life spans, contrails are a difficult study subject.

“The greatest impediment to understanding the contrail impacts on weather and climate is the poor state of knowledge of humidity in the upper troposphere [3.8 to 9.3 miles/6 to 15 kilometers in altitude],” NASA’s Minnis said.

“Until we can measure it properly and extensively, and model it and its interaction with cirrus clouds and contrails, we will continue to have large uncertainties about the effect of contrails.”

Winter is Contrail Season

At the high altitudes favored by commercial airlines, the air is much more humid in winter, so contrails are twice as likely in that season, study co-author Stuber said.

“We also found that flights between December and February contribute half of the annual mean climate warming, even though they account for less than a quarter of annual air traffic,” she said of her U.K.-based research.

Study leader Piers Forster, of England’s University of Leeds, suggests that contrails’ current impact on the atmosphere is likely to increase as air traffic grows. […]”<

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