The planet is hurtling towards a disturbing milestone as researchers predict that the southern hemisphere “within days” will reach a new atmospheric baseline of 400 parts per million (ppm) of carbon, signifying that humanity has entered a new phase in our climate impact.
“Once it’s over [400 ppm], it won’t go back,” Paul Fraser, a retired fellow with Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO), told the Sydney Morning Herald on Tuesday. “It could bewithin 10 days.”
The symbolic climate threshold is expected to be recorded at the Cape Grim monitoring site, on the northwestern point of Tasmania, which is jointly run by CSIRO and the Bureau of Meteorology and said to capture “the most accurate reading of the atmospheric conditions in the southern hemisphere.” On May 6, a CSIRO team took a reading of 399.9 ppm.
The 400 ppm milestone has been reached before. First, in May 2013 at the National Oceanic and Atmospheric Administration’s (NOAA) observatory in Mauna Loa, Hawaii and later in Alaska. But, in both those cases, the carbon concentration later dipped back down with the seasonal cycle. Unfortunately, as Fraser warned, this new record may be here to stay. The Herald explains: