For the first time, measurements of atmospheric carbon dioxide (CO2) taken at Mauna Loa Observatory in Hawaii exceeded 400 parts-per-million on an hourly basis. It's a symbolic benchmark, but an important one, suggesting that efforts to curb greenhouse gas emissions have not yet shown any significant effect.
The Sydney Morning Herald reports on the significance of the new readings.
The daily CO2 level, measured at the Mauna Loa Observatory in Hawaii, was 399.72 parts per million last Thursday, and a few hourly readings had risen to more than 400 parts per million. …
The last time CO2 reached the symbolic milestone of 400 parts per million in the atmosphere - in the Pliocene era - temperatures rose by between 3 and 4 degrees and sea levels were between five and 40 metres higher than today. Carbon dioxide levels have been rising steadily since constant measurements began at the Hawaiian observatory in 1958, when the level was about 317 parts per million.
We're hitting that mark sooner than we anticipated. Last month, Peter Gleick of the Pacific Institute wrote an article titled, "An Inevitable Headline in 2014: Planet’s CO2 level reaches 400 ppm for first time in human existence." Gleick was overly optimistic. Over the past two decades, the rate at which carbon dioxide has collected in the atmosphere has increased slightly.