Politico: The amount of heat-trapping carbon dioxide in the atmosphere passed a symbolic milestone this week, scientists announced Friday, reaching levels that havent prevailed on the Earth since long before human civilization began.
The long-expected announcement by the National Oceanic and Atmospheric Administration that CO2 concentrations had finally hit 400 parts per million at a key measuring station in Hawaii means little by itself. But its a sign that time is slipping away to head off or lessen...