Carbon Dioxide Levels

The following explains how carbon dioxide levels in the atmosphere have been monitored for the past 50+ years at the Mauna Loa station. When done viewing, click on "Related" and then" A Scientist, His work and a Climate Reckoning" for a more detailed article about Keeling and monitoring the atmosphere.

http://www.nytimes.com/interactive/2010/12/22/science/earth/20101222-carbon/index.html