Mongabay: For the first time in human history, carbon dioxide concentrations averaged out at 400 parts per million (ppm) worldwide in March, according to NOAA. Carbon dioxide concentrations have likely not hit such levels in two million years-long before Homo sapiens evolved.
"This marks the fact that humans burning fossil fuels have caused global carbon dioxide concentrations to rise more than 120 parts per million since pre-industrial times," said Pieter Tans, lead scientist of NOAAs Global Greenhouse...