On Wednesday it incorporated the final weeks of a year ago into its climate models and concluded that average global surface temperature in 2018 was 1 degree Celsius (1.8 Fahrenheit) above pre-industrial baseline levels.
This is also seen as a critical threshold for climate change, as it represents the lower bound of the average temperature rise.
The UN's World Meteorological Organization said in November that 2018 was set to be the fourth warmest year in recorded history, stressing the urgent need for action to rein in runaway planetary warming. NASA said the Earth's global surface temperatures last year were the fourth warmest in nearly 140 years, with the warming trends strongest in the Arctic region.
Last December was the second-warmest December in the 139 years that records have been kept.More news: Amazon's Jeff Bezos accuses National Enquirer publisher of extortion and blackmail
"2018 is yet again an extremely warm year on top of a long-term global warming trend", GISS Director Gavin Schmidt said in a statement on Wednesday. Meanwhile, record levels of man-made greenhouse gas emissions, mainly from burning fossil fuels, trap ever more heat.
Both organisations contributed data to the WMO.
In addition to continuing a trend toward warmer average global temperatures, 2018 saw multiple changes or natural disasters thought to be linked to climate change, including melting of ice north of Greenland that normally stays frozen year-round; a heat wave in Australia that killed tens of thousands of wild animals; and an unusually devastating fire season in the western US.More news: Actor Albert Finney Dies Aged 82
The WMO said sharp temperatures also contributed to a number of extreme weather events such as hurricanes, droughts and flash flooding over various regions of the world.
January 1 to December 31, 2018, according to NASA. The Paris pact responded to a 1992 United Nations treaty under which all governments agreed to avert "dangerous" man-made climate change.
Patrick Verkooijen, head of the Global Center on Adaptation in the Netherlands, said that the WMO report showed "climate change is not a distant phenomenon but is here right now".More news: NZ vs Ind 2nd T20: Hosts win toss and opt to bat