The World Meteorological Organisation said the global average temperature in January-October was 0.57 Celsius (1.03 Fahrenheit) above average, the same as in record hot year 2010.
The ocean temperature set a new record in the nine-month period, while land temperatures were the fourth or fifth highest since record-keeping began in the 19th century, the WMO said in a report released at UN climate talks in Lima and at its headquarters in Geneva.
"The provisional information for 2014 means that 14 of the 15 warmest years on record have all occurred in the 21st century," WMO Secretary-General Michel Jarraud said in a statement. "There is no standstill in global warming."
Michael Oppenheimer of Princeton University said the long-term warming trend is combined with natural variations that tend to be cyclical, with a period of lower-than-average warming followed by a period of rapid warming.
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Ocean temperatures were particularly high in the northern hemisphere from June to October.
"Around 93 percent of the excess energy trapped in the atmosphere by greenhouse gases from fossil fuels and other human activities ends up in the oceans. Therefore, the heat content of the oceans is key to understanding the climate system," the WMO said.
By November 13 there had been 72 tropical storms, well below the average of 89.
Arctic sea ice shrunk to the sixth lowest level on record in September, while Antarctic sea ice grew to a record extent for the third straight year.
The concentration in the atmosphere of carbon dioxide, a key greenhouse gas, rose to a new high of 396 parts per million last year, the WMO said, 142 percent above the level before the industrial revolution, when people started burning fossil fuels for energy. Figures for 2014 were not yet ready.