"This result shows the increased cirrus (cloud) coverage, attributable to air traffic, could account for nearly all of the warming observed over the United States for nearly 20 years starting in 1975," said Patrick Minnis, a senior research scientist at NASA's Langley Research Center in Hampton, Virginia.

Such "contrails", which are believed to actually cause the increase in cirrus cloud according to the study's findings, would "add to, and not replace, any greenhouse gas effect," he said.

During the same period, "warming occurred in many other areas where cirrus coverage decreased or remained steady."

A one percent increase per decade in cirrus cloud cover above the United States was "likely" due to air traffic-induced contrails, he said.

The study, published in the April 15 edition of the US review, the Journal of Climate, demonstrates that human activity has a visible and significant impact on cloud cover and, therefore, on climate," Minnis said.

"It indicates that contrails should be included in climate change scenarios," the National Aeronautics and Space Administration researcher added.

SPACE.WIRE