The amount of carbon dioxide in Earth's atmosphere has topped 400 parts per million, two months earlier than levels crossed that threshold in 2013. In 2013, carbon dioxide in the Earth's atmosphere topped 400 ppm for the first time but did not cross that marker until mid-May. This puts CO2 levels on the fast track to break another record by summer. "We're already seeing values over 400. Probably we'll see values dwelling over 400 in April and May. It's just a matter of time before it stays over 400 forever," said Ralph Keeling, who runs a carbon dioxide monitoring program for Scripps Institute of Oceanography. Keeling took over the running of the program from his father at the Mauna Loa Observatory in Mauna Loa, Hawaii. Since the program began monitoring CO2 levels in March 1958. atmospheric carbon dioxide levels have steadily risen from 313 ppm as humans continue to burn fossil fuels and increase industrialization. The higher levels will continue to contribute to rising ocean temperatures, melting ice caps, and more extreme weather.