Guardian: Were officially living in a new world. Carbon dioxide has been steadily rising since the start of the Industrial Revolution, setting a new high year after year. Theres a notable new entry to the record books. The last station on Earth without a 400 parts per million (ppm) reading has reached it. A little 400 ppm history. Three years ago, the worlds gold standard carbon dioxide observatory passed the symbolic threshold of 400 ppm. Other observing stations have steadily reached that threshold...