Levels of heat-trapping greenhouse gases in the atmosphere have reached another new record high, according to the World Meteorological Organization (WMO). There is no sign of a reversal in this trend, which is driving long-term climate change, sea level rise, ocean acidification and more extreme weather. The WMO Greenhouse Gas Bulletin showed that globally averaged concentrations of carbon dioxide (CO2) 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.