According to NOAA findings, Europe in particular experienced its "warmest year on record", as many countries, including France, Germany and Switzerland, dealt with their hottest 12 months in recent history.
According to NOAA, 2016 was the warmest year on record, followed by 2015 and 2017 in second and third place.
"Over the next five years there is a one in 10 chance of one of those years breaking the (1.5C) threshold", Professor Adam Scaife of the Met Office told Reuters of the agency's medium-term forecasts.
2018, it turns out, broke quite a few records, none of them good.
The average global temperature during 2018 was 1.42 degrees F above the 20th-century average.
On Wednesday it incorporated the final weeks of previous year into its climate models and concluded that average global surface temperature in 2018 was 1 degree Celsius (1.8 Fahrenheit) above pre-industrial baseline levels.
"2018 is yet again an extremely warm year on top of a long-term global warming trend", said GISS Director Gavin Schmidt.
The US temperature past year was the 14th-warmest on average, NOAA climate monitoring chief Deke Arndt said.
Along with this, Nasa and the National Oceanic and Atmospheric Administration have also released new figures for global warming.
The report also noted that warming is being felt most in the Arctic, where sea ice continues to melt, raising the sea level.
The British Met Office said temperatures could rise to 1.5C above pre-industrial times, for instance if a natural El Nino weather event adds a burst of heat.
"This warming has been driven in large part by increased emissions into the atmosphere of carbon dioxide and other greenhouse gases caused by human activities", NASA said in a statement.
NASA's global temperature analyses use surface temperature recordings from 6,300 weather stations around the world, incorporating ship- and buoy-based measurements of ocean surface temperatures as well as measurements of surface temperatures from Antarctic research outposts.