Scientists from around the world have said that 2017 was the hottest on record without the influence of an "El Nino" weather pattern.
Figures from a number of different international analyses show that, overall, 2017 was one of the three hottest years on record, with temperatures around 1.1 degree Celsius above pre-industrial levels.
Last year's temperatures were outstripped only by the record heat of 2016, and in some of the analyses by 2015.
Both 2016 and 2015 saw a significant El Nino, a natural phenomenon in the Pacific Ocean that increases temperatures on top of human-induced global warming.
The main contributor to the rising temperatures over the last 150 years is human activity, such as burning fossil fuels which puts heat-trapping greenhouse gases into the atmosphere, the scientists said.
The World Meteorological Organisation (WMO), which brings together five leading international data sets, said temperatures were on the rise over the long term.
WMO secretary-general Petteri Taalas said: "The long-term temperature trend is far more important than the ranking of individual years, and that trend is an upward one."
"Seventeen of the 18 warmest years on record have all been during this century, and the degree of warming during the past three years has been exceptional."
Mr Taalas said: "Arctic warmth has been especially pronounced and this will have profound and long-lasting repercussions on sea levels, and on weather patterns in other parts of the world."
2017's warm temperatures were accompanied by extreme weather in many countries around the world.
The US had its most expensive year ever in terms of weather and climate disasters, while other countries saw their development slowed or reversed by tropical cyclones, floods and drought.