Increase in incoming thermal energy bears signature of greenhouse gas
For the first time, scientists have witnessed a direct connection between rising levels of atmospheric carbon dioxide and an increase in the amount of thermal radiation striking Earth’s surface. The work affirms a cornerstone of the theory that humans have contributed to worldwide warming in recent decades, the researchers report online February 25 in Nature.
Carbon dioxide, like other greenhouse gases, can absorb and reradiate infrared light back down to Earth. This process traps thermal energy around the planet that would otherwise escape into space. To uncover how large an effect recent CO2 increases have had on Earth’s energy balance, climate scientist Daniel Feldman of the Lawrence Berkeley National Laboratory in California and colleagues monitored the amount of thermal radiation hitting two sites in Alaska and Oklahoma on cloudless days. Because CO2 emits light within a signature range