Key observing station reports 400 ppm for atmospheric carbon dioxide

Science : The carbon dioxide monitoring station at Cape Grim, on the northwestern tip of Tasmania, recorded readings above 400 ppm for four consecutive days last week, according to Paul Krummel of Australia’s Commonwealth Scientific and Industrial Research Organisation. That level stands in stark contrast to the baseline of 280 ppm for atmospheric CO₂, the level at the beginning of the industrial age 200 years ago. Scientists estimate that a level of 450 ppm would correspond to a global temperature increase of 2 °C, the maximum increase allowable to avoid the most devastating consequences of global warming. Cape Grim isn’t the first monitoring station to pass 400 ppm; an outpost on Mauna Loa in Hawaii reached that mark in 2013 and has occasionally done so ever since. Unlike the Mauna Loa station, the Cape Grim station is not as significantly affected by seasonal changes that cause regular rises and falls in CO₂ levels. Cape Grim is also located at a latitude where strong winds perpetually blow, which prevents localized buildups of pollution. As such, measurements taken at the station are used as a proxy for global CO₂ levels.