Carbon dioxide content in the air was 401.84 parts per million (ppm) on March 9. Measurements are taken daily at the Mauna Loa Observatory in Hawaii. A year ago the measurement was 398.40 ppm. The annual daily CO2 content in 2014 was 398.55. For 2013 the number was 396.48. The value for the first week of March 10 years ago was 381.56.
The project is under the direction of the Scripps Institution of Oceanography at the University of California at San Diego. You can find more information at www.http://scrippsco2.ucsd.edu/data/in_situ_co2/weekly_mlo.csv%20