Energy Collective: The World Meteorological Organization reports that, for the first time in human history, atmospheric concentrations of carbon dioxide (CO2) eclipsed 400 parts-per-million (ppm) in the northern hemisphere for the entire month of April. CO2 concentration vary with the seasons, generally reaching their highest level early in the northern hemispheres spring before seasonal intake of CO2 from vegetation. The first recording of 400 ppm occurred briefly in the spring of 2012 at the National Oceanic and...