Global CO2 Concentration Passes Threshold of 400 ppm—And That’s Bad for the Climate

Scientists say humans may need to take some carbon dioxide out of the atmosphere to stop global warming

The average level of carbon dioxide in the atmosphere across the globe passed 400 parts per million (ppm) last year, a symbolic and worrying milestone in growth of manmade climate change, the World Meteorological Organization (WMO) confirmed Monday.

The carbon dioxide concentration is unlikely to dip below the 400 ppm mark for at least several decades, even with aggressive efforts to reduce global carbon emissions, according to the WMO report, which confirms similar findings reported last month. Carbon dioxide can last in the atmosphere for thousands of years without efforts to remove it.

“The year 2015 ushered in a new era of optimism and climate action,” said WMO Secretary-General Petteri Taalas, referring to the landmark Paris Agreement to address climate change. “The real elephant in the room is carbon dioxide, which remains in the atmosphere for thousands of years and in the oceans for even longer.” Read more…