Last year was the second or third warmest ever recorded, despite an absence of the natural temperature-boosting El Niño phenomenon and the onset of its cooling counterpart La Niña.
That is according to provisional figures from the Met Office, which show that the global mean temperature for 2017 was between 0.32˚C and 0.56˚C above the long-term 1981-2010 average.
The two other hottest years were 2015 and 2016, but both of these were influenced by a significant El Niño event.
Had this not been the case, it is thought that 2017 would have been the warmest on record, with the data backed up by estimates from NASA and the National Oceanic and Atmospheric Administration (Noaa).
“The global temperature figures for 2017 are in agreement with other centres around the world – 2017 is the warmest since 1850 without the influence of El Niño,” Dr Colin Morice of the Met Office Hadley Centre said.
The data is compiled from many thousands of temperature measurements taken across the globe, from all continents and all oceans.
It shows that last year was 0.99˚C (±0.1°C) above pre-industrial levels, taken as the average over the period 1850-1900, and 0.38˚C (±0.1°C) above the 1981-2010 average.
The El Niño event spanning 2015-2016 is estimated to have contributed around 0.2°C to the annual average for 2016, which was about 1.1°C above the long-term average from 1850 to 1900.
However, the scientists said the main contributor to warming over the last 150 years is human influence on climate from increasing greenhouse gases in the atmosphere
The previous forecast made by the Met Office at the end of 2016 correctly predicted that last year would be one of the hottest ever.
The Noaa and Met Office judge 2017 to be the third warmest since records began, and NASA rate it as the second hottest, although it is agreed that the five warmest years have taken place since 2010.
“Despite colder than average temperatures in any one part of the world, temperatures over the planet as a whole continue the rapid warming trend we've seen over the last 40 years,” NASA climatologist, Gavin Schmid, said.
