Climate change: Warming gas concentrations at new record high

Concentrations of key gases in the atmosphere that are driving up global temperatures reached a new high in 2017. In their annual greenhouse gas bulletin, the World Meteorological Organization (WMO) says there is no sign of reversal in this rising trend.

Carbon dioxide levels reached 405 parts per million (ppm) in 2017, a level not seen in 3-5 million years. Researchers also note the resurgence of a banned chlorofluorocarbon gas called CFC-11.

Concentrations differ from emissions in that they represent what remains in the atmosphere after some of the gases are absorbed by the seas, land and trees. Since 1990 the warming impact of these long lived gases on the climate has increased by 41%.

“I am very concerned that the three greenhouse gases most responsible for climate change (CO2, methane, and nitrous oxide) are all rising upwards unabated,” said Prof Corinne Le Quéré from the University of East Anglia. “CO2 concentrations are now well above 400ppm – levels were 321ppm when I was born, that is a big rise in a human lifetime!”

Methane is the second most important greenhouse gas, and about 60% of it in the atmosphere comes from human activities like cattle farming, rice cultivation and fossil fuel extraction. Levels in the atmosphere are now about 1,859 parts per billion – 257% of what they were before the industrial revolution, and the rate of increase is pretty constant over the last decade.

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