A federal science agency says that levels of the main global warming gas have shot past a key milestone. Friday’s announcement by the National Oceanic and Atmospheric Administration says the amount of carbon dioxide in the atmosphere in May averaged 421 parts per million. That’s more than 50% higher than pre-industrial levels. NOAA says carbon dioxide levels in the air in May have reached a point last known when Earth was 7 degrees hotter, millions of years ago. Carbon dioxide levels peak in May of the year and drop as plants suck up more of the heat-trapping gas.
Sky high: Carbon dioxide levels in air spike past milestone
