All Eyes on Keeling Curve: Scientists Anxious as CO2 Levels to Cross 400 PPM

For the first time in human history, concentrations of carbon dioxide in the atmosphere are expected to pass 400 parts per million across much of the Northern Hemisphere in May, according to scientists who study data from the Mauna Loa Observatory, the world's longest-running CO2 monitoring station.

While crossing the 400 ppm mark isn't a "tipping point" that signals climate catastrophe, scientists told InsideClimate News, it is an important symbolic milestone that underscores government inaction on global warming. 

"This is another global emissions target that we've blown past without doing anything," said Jim Butler, director of global monitoring at NOAA's Earth System Research Laboratory. "Stronger storms, droughts, rising seas. We are already seeing the impacts of increased CO2 in the atmosphere ... How much further can we really go?" The NOAA lab operates the Mauna Loa Observatory and dozens of other greenhouse gas monitoring sites across the globe

read more