New Milestone for CO2 Levels: Mauna Loa Observatory Records 400 PPM

We’ve hit 400 ppm of carbon dioxide, but we won’t know what that means for decades.

http://www.technologyreview.com/view/514811/new-milestone-for-co2-levels-mauna-loa-observatory-records-400-ppm/?utm_campaign=newsletters&utm_source=newsletter-weekly-energy&utm_medium=email&utm_content=20130513