The World Meteorological Organization said 2012 was the ninth warmest year on record despite a cooling La Nina weather pattern earlier in the year. It also marked the 27th consecutive year that global temperatures were higher than the 1961-90 average.
WMO Secretary-General Michel Jarraud said the trend was troubling despite seasonal fluctuations that occur naturally on a regular basis.
"The continued upward trend in atmospheric concentrations of greenhouse gases and the consequent increased radiative forcing of the Earth's atmosphere confirm that the warming will continue," he said in a statement.
WMO said there was a record loss of summer sea ice last year, an increase in sustained drought and extreme weather events that may be tied to warming trends.
Hurricane Sandy, a late 2012 storm, formed over Atlantic waters that were warmer than the seasonal average.
International Energy Agency Executive Director Maria van der Hoeven said last month that the global energy sector, in general, was "as dirty as it was 20 years ago" despite the increase in the use of renewable energy resources. The IEA attributed this in large part to the continued use of coal as an energy source.