415ppm
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CO2 levels are the highest since humanity began
CO2 levels on Earth have officially hit 415 parts per million (ppm), according to readings taken at the Mauna Loa Observatory in Hawai'i. That's the highest level since homo sapiens came onto the planet, meteorologist Eric Holthaus tweeted, and represents an increase of 15 ppm over just the past three years. "We don't know a planet like this," Holthaus said.