For the past week, concentration of co2 in the atmosphere, measurements from Mauna Loa Observatory in Hawaii, in parts per million (ppm):

December 31 - 399.57 ppm
December 30 - 398.89
December 29 - 398.93
December 28 - 398.64
December 27 - 398.38

Weekly value one year ago, Dec. 31, 2013 — 397.26 ppm
Weekly value 10 years ago — 377.78 ppm
800,000 years ago — 260 ppm