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CO2 levels breach 400 ppm, to remain for our lifetime

CO2 concentration levels in the atmosphere have risen above 400 parts per million (ppm) for the second year in succession, but this time they will endure for our lifetimes, according to scientists at the Mauna Loa Observatory in Hawaii, global record-keeper of carbon emissions since the 1950s.

“Our forecast supports the suggestion that Mauna Loa record will never again show CO2 concentrations below the symbolic 400 ppm within our lifetime,” said a recently-published study conducted by scientists from UK’s Met Office Hadley Centre and Ralph Keeling of the Scripps Institution of Oceanography in La Jolla, California, and published in Nature Climate Change.

CO2 levels breached the 400 ppm level last year as well, but when scientists last studied the data during September and October 2015, CO2 at Mauna Loa was below 400 ppm (latest reading for week ending June 26, 2016 was 406.23).

“Knowing that CO2 levels have passed this threshold feels quite profound, showing again that humans have made their mark on the Earth’s climate,” Professor Richard Betts of the Met’s Hadley Centre and Exeter University and the lead author of the study told IndiaSpend. “My first reaction was a small sense of nostalgia and even sadness, realising that this was probably the last time those numbers would be measured there.”

The paper predicts increasing CO2 concentration in the atmosphere. High levels of CO2 and other gases-methane, nitrous oxide, ozone-and water vapour turn the atmosphere into a greenhouse, which lets in sunlight and traps heat that would otherwise escape into space.

This greenhouse effect has driven up the earth’s average surface temperature from 0.6 to 0.9 degrees C between 1906 and 2005, the rate of temperature increase nearly doubling over the last 50 years, according to the Earth Observatory of the National Aeronautics and Space Administration.

The 400-ppm level does not have immediate implications. “We did feel that it was a small but significant moment, realising that we had just passed through that threshold,” said Betts.

The record CO2 rise – 3.1 ppm against the annual average of 2.1 ppm – this year has both natural and human origins, the study said.

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