The next five years are likely to see temperatures of 1C or more above pre-industrial levels as the Earth experiences its warmest decade on record, the Met Office said.
Average global surface temperatures for 2019 to 2023 are forecast to be between 1.03C and 1.57C above the levels seen before the Industrial Revolution, the experts said.
If temperatures over the next five years are in line with the predictions, it will make the decade between 2014 and 2023 the hottest run of years in records reaching back to 1850.
The forecast is being made as climate experts around the world release information on global temperatures in 2018.
The World Meteorological Organisation (WMO) said analysis of five leading international datasets showed the global average temperature last year was approximately 1C above pre-industrial levels of 1850-1900.
It means it was the fourth hottest year on record, coming behind only 2016, 2015 and 2017, and making the last four years the warmest recorded.
Professor Adam Scaife, head of long-range prediction at the Met Office, said: "2015 was the first year that global annual average surface temperatures reached 1C above pre-industrial levels, and the following three years have all remained close to this level.
"The global average temperature between now and 2023 is predicted to remain high, potentially making the decade from 2014 the warmest in more than 150 years of records."
Countries have pledged to pursue efforts to curb global temperature rises to 1.5C above pre-industrial levels under the Paris Agreement on climate change.
But with a trend predicted of the world being near or more than 1C above pre-Industrial Revolution levels over the next few years, average global temperatures could temporarily exceed the 1.5C level, the experts said.
Dr Doug Smith, Met Office research fellow, said: "A run of temperatures of 1C or above would increase the risk of a temporary excursion above the threshold of 1.5C above pre-industrial levels.
"Predictions now suggest around a 10% chance of at least one year between 2019 and 2023 temporarily exceeding 1.5C."
WMO secretary-general Petteri Taalas said the long-term trend is an upward one.
"The 20 warmest years on record have been in the past 22 years. The degree of warming during the past four years has been exceptional, both on land and in the ocean.
"Temperatures are only part of the story. Extreme and high-impact weather affected many countries and millions of people, with devastating repercussions for economies and ecosystems in 2018."
Prof Sir Brian Hoskins, chair of the Grantham Institute, Imperial College London, said: "Our lack of decisive action over climate change makes us like a climber ascending a mountain, knowing that there will not be enough oxygen at some height, yet still we go on.
"Not every individual step takes us nearer disaster, but as confirmed by the Met Office, our general direction is clear."