The World Meteorological Organisation says there's a growing chance that global temperatures will rise by more than 1.5C over the next five years, compared to pre-industrial levels.
It assesses a 20% chance the threshold will be broken in one year before 2024 and a 70% chance it will be broken in one or more months in those five years.
Scientists say it shows the tough task of controlling climate change levels.
The 2015 Paris accord had tasked world leaders with certain goals.
It committed them to pursue efforts to try to keep the world from warming by more than 1.5C this century.
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This new assessment, carried out by the UK's Met Office for the World Meteorological Organisation (WMO), says there's a growing chance that this level will be breached.
Researchers say that the Earth's average annual temperature is already more than 1C higher than it was in the 1850s - and will probably stay around this level over the next five years.
Previous studies had put the short-term chances of going above 1.5C at 10% - that's now doubled say the climate modellers, and it's increasing with time.
Some parts of the world will feel this rising heat more than others, with the scientists saying that the Arctic will probably warm by twice the global average this year.
They also predict that over the coming five years there will be more storms over western Europe thanks to rising sea levels.
The assessment considers natural variability as well as the impact of carbon emissions from human activities - however the models don't take account of the fall-off in CO2 emissions caused by the coronavirus pandemic.
The WMO says this is unlikely to affect temperatures in the early 2020s.
