Climate Change & Global Warming

The annual average concentration of carbon dioxide (CO2) in the atmosphere stood at 395.3 parts per million (ppm) in 2013—a 27 percent increase compared to conditions before the Industrial Revolution. On May 9, 2013, the daily average concentration of CO2 surpassed 400 ppm for the first time at the Mauna Loa Observatory in Hawaii.

April 2013

  • Much colder-than-average temperature during March and a strongly negative Arctic Oscillation Index reminded people in the United States how important this index is to our own climate conditions.