USA Today: Worldwide levels of carbon dioxide - the gas scientists say is most responsible for global warming - reached a significant milestone for the month of March, the National Oceanic and Atmospheric Administration said Wednesday.
The global monthly average for carbon dioxide hit 400.83 parts per million in March, the first time the average surpassed 400 ppm for an entire month since such measurements began in the late 1950s, NOAA said.
"It's both disturbing and daunting," said NOAA chief greenhouse...