|Scientists who measure and forecast the concentrations of greenhouse gases in the atmosphere said on Monday, June 13 that we may have passed a key turning point. Humans walking the Earth today will probably never live to see carbon dioxide concentrations in the atmosphere once again fall below a level of 400 parts per million.|
Carbon dioxide concentrations in the pre-industrial atmosphere were around 280 ppm. But concentrations began to rise with the early growth of industry and continually climbed throughout the 20th century, as documented by the famous Keeling curve, based on observations taken at Mauna Loa dating back to the late 1950s.
Mauna Loa Observatory | Atmospheric CO2 Concentrations
daily mean concentrations | ppm = parts per million
|The paper predicts that this El Niño will drive a year-to-year rise in average atmospheric concentrations of 3.15 ppm, exceeding the single-year change caused by the last major El Niño, from 1997 to 1998, of 2.9 ppm.|
On June 12, concentrations were at 407.26 ppm. They should start to decline soon, according to the seasonal cycle, which reaches a peak in May and a low in September and is driven by the growth of plants in the northern hemisphere.
Atmospheric carbon dioxide concentrations will continue to rise even though global greenhouse gas emissions from industry may be leveling off somewhat, the study adds — because each year still represents a net addition to the atmosphere, and carbon dioxide is a very long-lived greenhouse gas.