The global average surface temperature in 2015 is likely to be the warmest on record and to reach the symbolic and significant milestone of 1° Celsius above the pre-industrial era. This is due to a combination of a strong El Niño and human-induced global warming, according to the World Meteorological Organization (WMO). The years 2011-2015 have been the warmest five-year period on record, with many extreme weather events - especially heatwaves - influenced by climate change, according to a WMO five-year analysis.