Global CO2 Levels Approach Worrisome Milestone

http://www.scientificamerican.com/article.cfm?id=global-co2-levels-approach-worriesome-milestone&WT.mc_id=SA_emailfriend

Concentrations of greenhouse gases in Earth's atmosphere will surpass 400 parts per million in the next month. Nations could have a hard time keeping global warming in check at that level

By Richard Monastersky and Nature magazine