Global Warming Engineered By Chemtrails?

Whether the jet set should grab a hair shirt over global warming is, well, a heated topic. The airline industry insists commercial airplanes, when tracked by the fuel needed per kilometre travelled per passenger, are on par with a fuel-efficient hybrid car. Air travel is responsible for about 2 per cent of global-warming emissions.

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The controversy stems from the fact that high-altitude emissions - from nine to 13 kilometres up for subsonic flights and higher for supersonic - cause disproportionately more warming than those at ground level, anywhere from 50 per cent to four times as much, making its global-warming role more significant than its emissions tally alone would indicate.

Part of the worry is due to contrails, the thin vapour trails from jets that crisscross the sky above many of the world's most-travelled air routes. Contrails resemble artificial cirrus clouds, trapping heat, although there is no scientific consensus about the size of their leavening effect on global warming.

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