The period from 2015 to 2019 was the hottest five-year period since records began about 150 years ago, according to the World Meteorological Organization (WMO).
Preliminary calculations released on Sunday showed that the average temperature in this period was 1.1 degrees Celsius warmer than the pre-industrial average.
Compared to the previous five years, average temperatures were higher by 0.2 degrees, the WMO report said.
The figures were released a day before the start of a climate summit in New York, hosted by UN Secretary General Antonio Guterres.
In order to meet the target of keeping the global temperature rise to less than 2 degrees by 2100, efforts to reduce greenhouse gases will have to be tripled, said WMO director general Petteri Taalas.
The signs and impacts of climate change – such as sea level rise, ice loss and extreme weather – increased during 2015-2019, the WMO report said.