Gases driving up global temperatures reach a new high

The World Meteorological Organization (WMO) has published its Greenhouse Gas Bulletin, with damning conclusions that there is no evidence of any reduction or change to the rising trend. Indeed gases in the atmosphere that increase global temperatures reached a new high in 2017.

Globally averaged concentrations of carbon dioxide reached 405.5 parts per million (ppm) in 2017, up from 403.3 ppm in 2016 and 400.1 ppm in 2015. Concentrations of methane and nitrous oxide also rose, whilst there was a resurgence of a potent greenhouse gas and ozone-depleting substance called CFC-11, which is regulated under an international agreement to protect the ozone layer.

Since 1990, there has been a 41 per cent increase in total radiative forcing – the warming effect on the climate - by long-lived greenhouse gases. CO2 accounts for about 82 per cent of the increase in radiative forcing over the past decade, according to figures from the US National Oceanic and Atmospheric Administration quoted in the WMO Bulletin.

“The science is clear. Without rapid cuts in CO2 and other greenhouse gases, climate change will have increasingly destructive and irreversible impacts on life on Earth. The window of opportunity for action is almost closed,” said WMO secretary-general Petteri Taalas.

The Bulletin has a special section devoted to CFC-11 (trichlorofluoromethane). This is a potent greenhouse gas and a stratospheric ozone-depleting substance regulated under the Montreal Protocol. Since 2012 its rate of decline has slowed to roughly two-thirds of its rate of decline during the preceding decade. The most likely cause of this slowing is increased emissions associated with the production of CFC-11 in eastern Asia.

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