Carbon Dioxide Levels Reach a New Milestone
UP, UP and away. Parts of the planet have seen levels of carbon dioxide rise above 400 parts per million for the first time. Although it’s largely symbolic, the milestone is a stark reminder of humanity’s powerful influence on the atmosphere.
“During the month of April, the mean was over 400 ppm for the first time, throughout the Arctic,” says Pieter Tans of the US National Oceanic and Atmospheric Administration’s Earth System Research Laboratory in Boulder, Colorado. CO2 levels reach an annual peak around April as the gas is released by respiration, and then fall over the summer as plants suck it up. As a result, the 2012 average will be a little lower, at about 393 ppm.
Nevertheless, Tans says global levels will top 400 ppm in a few years.