The planet has hit a new high. This March, our monthly average carbon dioxide concentrations surpassed 400 parts per million globally. It’s the first time this has happened since we started tracking the greenhouse gas in the atmosphere, according to figures released by the National Oceanic and Atmospheric Administration (NOAA) this week.
“It was only a matter of time that we would average 400 parts per million globally,” Pieter Tans of NOAA’s Global Greenhouse Gas Reference Network says in a news release. “This marks the fact that humans burning fossil fuels have caused global carbon dioxide concentrations to rise more than 120 parts per million since pre-industrial times.” Half of that rise came about after 1980.
The first report of 400 ppm came when all of the network’s Arctic sites reached that value back in the spring of 2012. The next year, the Mauna Loa Observatory crossed that same threshold for the first time. “Reaching 400 parts per million as a global average is a significant milestone,”Tans adds. In fact, the last time it was this high, our species hadn’t evolved yet, the Guardian reports.