Carbon dioxide levels cross 400 ppm threshold, likely highest in millions of years

Carbon dioxide — the gas scientists say is most responsible for global warming — reached a significant symbolic milestone in our atmosphere this month, the Scripps Institution of Oceanography said. For the first time, daily and weekly values of carbon dioxide in our planet's atmosphere have remained above 400 parts per million, said Scripps scientist Ralph Keeling, keeper of his father's famed "Keeling Curve," the longest continuous record of atmospheric carbon dioxide on Earth.
http://www.usatoday.com/story/tech/sciencefair/2016/09/29/carbon-dioxide-levels-400-ppm-scripps-mauna-loa-global-warming/91279952/