"MIAMI - In another ominous sign of human-caused climate change, US government scientists said Wednesday that global carbon dioxide concentrations have reached a new monthly record of 400 parts per million.

Carbon dioxide is a potent greenhouse gas, and is a harmful by-product of burning fossil fuels such as oil and coal.

'For the first time since we began tracking carbon dioxide in the global atmosphere, the monthly global average concentration of this greenhouse gas surpassed 400 parts per million in March 2015,' said the National Oceanic and Atmospheric Administration (NOAA)."

AFP had the story May 7, 2015. [2]