"This represents a further potential area for action within the overall climate change challenge," said Steiner.

"An international group of modellers working with UNEP recently concluded that current commitments and pledges linked with the Copenhagen Accord are unlikely to keep a global temperature rise to under 2 degrees Celsius by 2050," he said.

"The gap between scientific reality and ambition is estimated to average around 4.7 gigatonnes of CO2 equivalent per year - a gap that needs to be urgently bridged over the next decade or so if the 2 degree C target is to be met."

Most climate scientists agree that keeping the global temperature rise to under 2 degrees Celsius is essential to averting the worst consequences of climate change - rising sea levels, extinction of species, extreme weather events, storms, floods, and droughts.

"The Montreal Protocol is an outstanding example of collaboration among scientists and decision-makers that has resulted in the successful mitigation of a serious environmental and societal threat," said WMO chief Jarraud.

"Human activities will continue to change the composition of the atmosphere," said Jarraud. "WMO's Global Atmosphere Watch program will therefore continue its crucial monitoring, research and assessment activities to provide scientific data needed to understand and ultimately predict environmental changes on both regional and global scales."