Wow, Fortean Times was right about something: Airplane contrails really are dangerous. The carbon emissions from air travel are profound, but the water vapor planes emit is just as bad, or worse. And airplane-spawned water vapor is what makes up the high, thin clouds known as contrails.

Michele Bachmann would surely object — water vapor is part of Earth’s life cycle! But water vapor that comes out of a plane’s butt actually acts like an atmospheric Snuggie, insulating the Earth and increasing warming. Contrails also inhibit the formation of regular cirrus clouds, which reduces the warming effect — but not enough to keep them from being one of the main reasons air travel contributes to global warming. Thank goodness that sky-writing fad went out years ago.

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