Wednesday, May 1, 2013

Atmospheric carbon dioxide about to reach 400ppm

As a new round of climate talks gets underway in the German city of Bonn, the NOAA's Earth Systems Research Observatory, perched high on Hawaii's Mauna Loa volcano, expects the CO2 level to reach 400 parts per million in the next few days. This site, at 3800 metres above sea level, far from densely populated areas with high CO2 emissions, has been monitoring carbon dioxide for half a century, and is considered the global reference location for these measurements.

This greenhouse gas normally shows its annual peak in the rising saw-tooth pattern in mid may, with the net annual peak level rising steadily year on year. It peaks before spring growth in the northern hemisphere starts to absorb the gas, releasing it during the northern winter. On April 25th the level reached 399.72ppm, and hourly readings have topped 400ppm six times in the last week. Charles Keeling, whose curve describes the rise in CO2 over the last half century said that if the line isn't passed in this year's peak, then it certainly will be next year. With two weeks to go before the annual peak, it seems likely that it will. The consensus safe level of atmospheric CO2 in the climate change community is considered to be 350ppm in order to keep Earth from warming less than two degrees Celsius. It has been over two million years since levels were this high, and the Pliocene world was much warmer than ours.

Image credit: NOAA.

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