Scientists have finally cracked the mystery behind one of climate change’s strangest fingerprints: while Earth’s surface heats up, the upper atmosphere is rapidly cooling. Researchers at Columbia University discovered that carbon dioxide acts very differently high above the planet, where it actually helps radiate heat into space instead of trapping it. The team found that certain infrared wavelengths fall into a “Goldilocks zone” that becomes increasingly effective as CO2 levels rise, accelerating cooling in the stratosphere.