Pexels While our emissions are trapping heat near the surface of the Earth, they are having the opposite effect in the upper atmosphere. For decades, the stratosphere has been cooling. A new study helps explain why. Down below, carbon dioxide absorbs infrared light and radiates heat, which drives warming. Higher up, carbon dioxide does the same, but because the air is thinner at altitude, much of the radiated heat escapes into space, with a cooling effect. Researchers have long been aware of this phenomenon , but they have been puzzled by the extent of cooling. Since the 1980s, temperatures in the stratosphere have dropped by roughly 2 degrees C, far more than they have risen down below.  The new modeling study sheds light on this mystery. It finds that as carbon dioxide accumulates, infrared light conveys heat more efficiently.…