A report compiled by a US government agency has confirmed that 2016 was the warmest year on record and the third year in a row of record global warmth.
The heat was the result of long-term global warming and a strong El Niño weather phenomenon, the report said.
Global surface and sea temperatures, sea levels and greenhouse gases levels were all at record highs, it added.
The report comes after President Donald Trump announced plans for the US to quit the 2015 Paris climate accord.
Mr Trump has previously dismissed climate change as “a hoax”.
The international report, State of the Climate in 2016, was compiled by the National Oceanic and Atmospheric Administration (NOAA) and is based on contributions from nearly 500 scientists from more than 60 countries.
It says that 2016 surpassed 2015 as the warmest year in 137 years of recordkeeping.
“Last year’s record heat resulted from the combined influence of long-term global warming and a strong El Niño early in the year,” the report said.
“The major indicators of climate change continued to reflect trends consistent with a warming planet.”
During an El Niño, a band of unusually warm ocean water develops in parts of the Pacific. The phenomenon affects the climate globally, disrupting weather patterns.
The report said that levels of carbon dioxide (CO2), methane and nitrous oxide – all the major greenhouse gases that drive global warming – had risen to new heights.
Global annual average atmospheric CO2 concentration was 402.9 parts per million (ppm) which surpassed 400 ppm for the first time in the modern atmospheric measurement record and in ice core records dating back as far as 800,000 years, the NOAA said.
“Climate change is one of the most pressing issues facing humanity and life on Earth,” it added.