The world is headed for its third warmest year on record, even without the boost from an El Nino, as the signs of climate change continue to mount, the World Meteorological Organisation said.

In a report released to coincide with the opening of the Bonn climate conference in Germany on Monday, the WMO said the five-year average was now running at about 1 degree warmer than the average for 1880-1900 period. The same conference two years ago in Paris agreed to keep warming to below 2 degrees.

Based on the first nine months of the year, 2017 is unlikely to match 2016 - the hottest year on record - or the previous year. Still, it is likely to dislodge 2014 as the third warmest.

Such a ranking for 2017 will be notable not least because El Nino Southern Oscillation (ENSO) conditions have been neutral this year, removing the warming boost the past two years had from an El Nino.