Atmospheric researchers flock to Summit Station, on the peak of the Greenland ice sheet, for purity: at 72 degrees north and 3,216 metres above sea level, the air is about as pristine as can be. This is the premiere spot to grab an air sample uncontaminated by local emissions. But more researchers are heading to the station these days, and with them come diesel generators, aeroplanes and snowmobiles. When the winds blow in the wrong direction, atmospheric scientists have to note in their data that a clean' sample might have been sullied by the very machinery that made its collection possible.
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