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An instrument near the summit of Mauna Loa in Hawaii has recorded a climate milestone: the amount of carbon dioxide in the atmosphere there has exceeded 400 parts per million (ppm) for the first time in 55 years of measurement—and probably more than 3 million years of Earth history.

While we, at Picarro, take a certain amount of pride in the instrument used to measure the amount of carbon dioxide, we share the concern this event causes. The chart (above right) from the Scripps Institution of Oceanography, UC San Diego, shows the carbon dioxide level hovering near 400 ppm in the first week of May. For all the details, read the National Geographic Daily News article Climate Milestone: Earth’s CO2 Level Passes 400 ppm.