I'm pouring a drink and toasting the sky tonight for this one. April 2014 is now the first complete month in human history (and likely more than 2 million years) with a global atmospheric average CO2 concentration above 400ppm. Last year saw the first day average, a few weeks ago we saw the first weekly average, and today makes the first month-long average for homo sapiens. Cheers to you and me.
http://www.weather.com/news/science/environment/april-first-month-co2-levels-above-400-ppm-20140430
