Ari Phillips, May 6, 2015
Four hundred: it’s a number that will go down in climate history while also continuing to rise.
According to the National Oceanic and Atmospheric Administration (NOAA), 400.83 parts per million (ppm) was the average concentration of atmospheric carbon dioxide in March. This news from NOAA marks the first time that the entire planet has surpassed the 400 ppm benchmark for an entire month.
With the rate of growth of atmospheric carbon dioxide concentrations steadily increasing — rising from about 0.75 ppm per year in 1959 to about 2.25 ppm per year in 2015 — this milestone will soon be surpassed. Still, the 400 ppm average has been a long time coming.
As the climate change activist group 350.org — named after what they deem to be a safe level of atmospheric carbon dioxide — states, at the beginning of human civilization the atmosphere contained about 275 ppm of carbon dioxide. This concentration began to rise during the Industrial Revolution in the 18th century, and the large-scale emissions of greenhouse gases into the atmosphere remains a critical part of human societies across the world.
NOAA takes these measurements from 40 isolated sites around the world that are far removed from local pollution sources that could disturb the data.
“Reaching 400 ppm doesn’t mean much in itself, but the steady increase in atmospheric greenhouse gases should serve as a stark reminder of the task facing politicians as they sit down in Paris later this year,” Ed Hawkins, a climate scientist at the University of Reading, told the Guardian..