The British office along with NOAA, NASA and the World Meteorological Organization analyze global temperatures in slightly different ways, but they all came to the same conclusion Wednesday: 2018 was the fourth-warmest year on record behind 2016, 2015 and 2017.
"2018 is yet again an extremely warm year on top of a long-term global warming trend", Gavin Schmidt, director of GISS, said in a statement.
While Australia just suffered through it's hottest January on record, around the world things aren't much better.
The new report said the world was on track to have average global temperatures rise to 3 degrees Celsius by 2100, as record levels of man-made greenhouse gas emissions, mainly from burning fossil fuels, is trapping more heat in the Earth's atmosphere.
Both organisations contributed data to the WMO.
Meanwhile, parts of the United States suffered bone-chilling cold from a blast of Arctic air last week.
New data confirms last year was one of the hottest ever recorded, and British meteorologists are predicting the next five years will be even hotter than 2018. The Paris pact responded to a 1992 United Nations treaty under which all governments agreed to avert "dangerous" man-made climate change.
"Over the next five years there is a one in 10 chance of one of those years breaking the threshold", Professor Adam Scaife of the Met Office said.
NOAA said the average temperature for the contiguous U.S.in 2018 was 53.5 degrees Fahrenheit, making it a warmer-than-average year for the 22nd year in a row.
A United Nations report previous year said the world is likely to breach 1.5C sometime between 2030 and 2052 on current trends, triggering ever more heat waves, powerful storms, droughts, mudslides, extinctions and rising sea levels.
"That is not saying the Paris Agreement is done for. but it's a worrying sign", he added.
U.S. President Donald Trump, who has cast doubt on mainstream climate science and promotes the coal industry, plans to withdraw the United States from the Paris Agreement.
He called for more, greener investments, ranging from defenses against rising seas to drought-resistant crops.