Global temperatures of 1.5° Celsius above pre-industrial levels are now more likely than not to happen within five years, scientists have said for the first time.

There is now a 66 per cent likelihood of breaching the key global warming threshold for at least a year by 2027, the World Meteorological Organisation said in its annual update.

The Paris Agreement on climate change aims to keep long-term temperature increases below 1.5° C, to avoid triggering irreversible tipping points.

Hitting 1.5° C in one year would not mean the world has failed to limit those long-term temperature rises, understood as a 20-year average.

But it does mean they are closer to happening, raising the prospect of tipping points such as the collapse of the West Antarctic Ice Sheet, which could cause massive sea level rise.

“We really are now within reach of a temporary exceedance of 1.5° for the annual mean, and that’s the first time in human history we’ve been that close,” said Prof. Adam Scaife, from the Met Office Hadley Centre. “So it shows we’re getting very, very close to the Paris threshold.”

“This report does not mean that we will permanently exceed the 1.5°C level specified in the Paris Agreement which refers to long-term warming over many years,” said Prof. Petteri Taalas, the WMO secretary-general.

“However, WMO is sounding the alarm that we will breach the 1.5°C level on a temporary basis with increasing frequency.” The chances of breaching the 1.5°C level in a single year have risen swiftly since 2015, the year the Paris Agreement was signed when they were close to zero. Last year the WMO suggested there was a 50-50 chance of hitting the record.

Global temperatures are also expected to break new records within the next five years.

The Daily Telegraph, London