Climate: World at risk of hitting temperature limit soon
Leon Hermanson, a senior Met Office scientist, told BBC News that comparing projected temperatures with those of 1850-1900 shows a clear rise.
"What it means is that we're approaching 1.5C - we're not there yet but we're getting close," he said.
The researchers point out that even if one of the next five years is 1.5C above the pre-industrial level, it'll be a temporary situation.
Natural variability will mean the following few years may be slightly cooler and it could be another decade or two or more before the 1.5C limit is crossed permanently.
The Paris Agreement established the goal of keeping the increase in the global average temperature to no more than 2C and to try not to surpass 1.5C - and that's understood to mean over a long period rather than a single year.
According to Dr Joeri Rogelj, director of research at the Grantham Institute, Imperial College London, "the 1.5C in the Met Office announcement should not be confused with the 1.5C limit in the Paris Agreement".
