The year 2018 is on course to be the fourth warmest on record, according to the World Meteorological Organization.
It says that the global average temperature for the first 10 months of the year was nearly 1C above the levels between 1850-1900.
The State of the Climate report says that the 20 warmest years on record have been in the past 22 years, with the 2015-2018 making up the top four.
If the trend continues, the WMO says temperatures may rise by 3-5C by 2100.
The temperature rise for 2018 of 0.98C comes from five independently maintained global data sets.
The WMO says that one of the factors that has slightly cooled 2018 compared to previous years was the La Niña weather phenomenon which is associated with lower than average sea surface temperatures.
Researchers say now that a weak El Niño is expected to form in early 2019 which might make next year warmer than this one.
Regardless of the impacts of these events, scientists say the long-term warming trend has continued in 2018 and they point to sea level rise, ocean acidification and glacier melt as examples of climate change.
"We are not on track to meet climate change targets and rein in temperature increases," said WMO Secretary-General Petteri Taalas.
"Greenhouse gas concentrations are once again at record levels and if the current trend continues we may see temperature increases 3-5C by the end of the century," he said.