According to this organization, the global average surface temperature may even reach the significant milestone of one degree Celsius above the pre-industrial era.
Experts affirmed that this temperature increase was due to the combination of the El Niño weather pattern with man-made global warming.
The 2011-15 period has been the warmest five-year period on record, with many extreme weather events, especially heat waves, influenced by climate change, WMO said.
The state of global climate in 2015 will make history for a number of reasons, WMO secretary-general Michel Jarraud said.
Levels of greenhouse gases in atmosphere reached new highs, and during spring 2015 in the northern hemisphere, the three-month global average concentration of carbon dioxide crossed the 400 parts per million barriers for the first time.
WMO issued its provisional statement on the status of the climate in 2015, and an additional five-year analysis for 2011-2015, to inform negotiations at the U.N. Climate Change Conference in Paris.
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