CO2 levels highest in human history

The concentration of carbon dioxide in the Earth's atmosphere has reached a record high, according to scientists at the Scripps Institution of Oceanography in the US.

The Mauna Loa Observatory in Hawaii recorded a carbon dioxide level of 415.39 parts per million (ppm) on Saturday, marking the first time a reading of the greenhouse gas has measured over 415 ppm.

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Carbon dioxide levels are normally higher in the Northern Hemisphere in fall, winter and spring. 

The last time there was more carbon dioxide in the atmosphere was more than 3 million years ago, when global average temperatures were 3 or 4 degrees Celsius (5.4-7.2 degrees Fahrenheit) higher than today, the oceans were several meters higher and parts of Antarctica supported forests.

The data has been recorded as part of the Keeling Curve, which started measurements in Mauna Loa in 1958. Since then, carbon dioxide concentrations in the atmosphere have risen 30%.

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Prior to the Industrial Revolution in the 19th century, carbon dioxide levels fluctuated but never exceeded 300 ppm at any one time over the past 800,000 years. Carbon dioxide levels in the atmosphere broke 400 ppm for the first time in human history in 2013.

Despite global commitments to reduce greenhouse gases under the 2015 Paris climate accord, the rate of heat trapping gases entering the atmosphere is accelerating. The last four years are the four hottest on record.

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Ralph Keeling, director of Scripps Institution of Oceanography's CO2 Program, said the trend would probably continue throughout 2019 with the possibility of an El Nino year in which temperatures rise due to warmer ocean currents.

"The average growth rate is remaining on the high end. The increase from last year will probably be around three parts per million whereas the recent average has been 2.5 ppm," he said. "Likely we're seeing the effect of mild El Nino conditions on top of ongoing fossil fuel use."

"Every year it goes up like this we should be saying 'No, this shouldn't be happening. It's not normal.' This increase is just not sustainable in terms of energy use and in terms of what we are doing to the planet," he said.

Under current emission trajectories, carbon dioxide in the atmosphere could reach 1,000 ppm over the next century, according to the Scripps Institution.

cw/cmk (AFP, dpa)

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