Record high CO2 levels to remain for decades
Concentrations of greenhouse gases in the atmosphere have reached levels never before seen in recorded history.
The World Meteorological Organisation (WMO) says the 400 parts per million (ppm) threshold was broken for the first time last year, but that concentrations will remain at this level for 2016 and "many generations" to come. The WMO says the levels have ushered in a "new era of climate change reality" - with the El Niño cycle partly to blame.
"CO2 levels had previously reached the 400 ppm barrier for certain months of the year and in certain locations, but never before on a global average basis for the entire year," the 'Greenhouse Gas Bulletin' says.
"The longest-established greenhouse gas monitoring station at Mauna Loa, Hawaii, predicts that CO2 concentrations will stay above 400 ppm for the whole of 2016 and not dip below that level for many generations."
Among the recent positive developments in tackling climate change include the signing of the Paris climate agreement last December. More recently, world leaders have agreed to phase out hydrofluorocarbons, used in air conditioning and refrigeration, which act as strong greenhouse gases.
"But the real elephant in the room is carbon dioxide, which remains in the atmosphere for thousands of years and in the oceans for even longer," WMO Director-General Petteri Taalas said.
"Without tackling CO2 emissions, we cannot tackle climate change and keep temperature increases to below 2C above the pre-industrial era. It is therefore of the utmost importance that the Paris Agreement does indeed enter into force well ahead of schedule on November 4 and that we fast-track its implementation," he said.
The growth spurt in CO2 was fuelled by the El Niño event, which started in 2015 and had a strong impact well into 2016. This triggered droughts in tropical regions and reduced the capacity of "sinks" like forests, vegetation and the oceans to absorb carbon.
"The El Niño event has disappeared. Climate change has not," Mr Taalas added.
The 'Greenhouse Gas Bulletin' was released by the WMO, which is part of the United Nations, in advance of the UN climate change negotiations, which take place in Morocco next month. The increase of CO2 from 2014 to 2015 was larger than the previous year, and the average over the previous decade, it adds.