Scientists treating Earth as a feverish patient are giving it the equivalent of a CAT scan, targeting short-life pollutants that spur climate change to try to find a remedy that dials back the heat. For the National Oceanic and Atmospheric Administration, University of Colorado and Harvard University scientists, this unprecedented airborne scan means looping around the planet in an instrument-packed NASA airliner that measures heat-trapping greenhouse pollutants. The aircraft — a modified white DC-8 with protruding tubes instead of windows — swooped over Boulder this week.