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    Jet trails may cause climate change: NASA

    WASHINGTON (AFP) Apr 28, 2004

    Condensation trails from the engine exhausts of jet aircraft may have provoked the warming trend in the climate seen from 1975 to 1994, a NASA researcher said Tuesday.

    "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.