Average global temperatures rose 1C above pre-industrial levels last year for the first time, the World Meteorological Organization in Geneva says.
The findings by the UN agency were 0.1C higher than those published by the US National Oceanic and Atmospheric Administration last week.
The UN agency, which incorporated official US and European data, agrees with the US agency that 2015 was the hottest year since Western record keeping began in the 19th century at the outset of the industrial revolution.
"It is a sobering moment in the history of our planet," said Petteri Taalas, the secretary general of the UN agency, on Monday.
The UN weather and climate body said last year's global average temperature rose 0.76C above the 1961-1990 average of 14C.
The years since 2011 had been the hottest five-year period on record, it added.
Last year's temperature rise was partly fuelled by an unusually strong El Nino, a weather phenomenon that warms the tropical Pacific Ocean and has been occurring every few years.
"The power of El Nino will fade in the coming months but the impacts of human-induced climate change will be with us for many decades," Taalas said.
He urged countries to improve early disaster-warning systems to prepare for expected extreme weather events.
