The United Nations World Meteorological Organisation (WMO) has warned that time is running out to cut rising greenhouse gas emissions, after atmospheric concentrations of carbon reached record levels last month.
In April, the WMO reported that monthly average concentrations of carbon dioxide in the atmosphere topped 400 parts per million (ppm) throughout the northern hemisphere for the first time in human history.
The measurements, backed up by earlier data recorded by the Scripps Institution of Oceanography at the University of California, are evidence of a rapidly rising trajectory.
Carbon dioxide levels have increased by more than 40% since people first started burning large quantities of fossil fuels about 250 years ago.
The UN Intergovernmental Panel on Climate Change (IPCC) previously warned that to avoid the most devastating impacts of climate change, the concentration of all greenhouse gases – including methane and other gases not counted in the new measurement – must not rise above 450 ppm this century.
The WMO now expects the global annual average carbon concentration to cross the 400ppm threshold in either 2015 or 2016. In light of this, the agency has warned that governments must act quickly.
“Time is running out,” WMO secretary-general Michel Jarraud said.
“This should serve as yet another wake-up call about the constantly rising levels of greenhouse gases which are driving climate change.
“If we are to preserve our planet for future generations, we need urgent action to curb new emissions of these heat-trapping gases.”
The UN will convene a summit of world leaders in September, which, it is hoped, will set the wheels in motion for the crucial UNFCCC Climate Change Conference in Paris in 2015.
In Paris, countries must conclude a global agreement on how to limit global warming to the agreed threshold of 2C from pre-industrial times.