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It is now “more likely than not” that the world will briefly overshoot its 1.5°C climate change target within five years, according to meteorologists at the UK Met Office.

There is a 66 per cent chance that at least one year from 2023 to 2027 will see an average global temperature more than 1.5°C above pre-industrial levels, the Met Office said in an analysis produced for the UN’s World Meteorological Organization (WMO).

This would mark the first breach of a threshold that was set to avoid the worst impacts of global warming.

In 2015, countries promised under the Paris Agreement to limit any global rise in average temperatures to “well below” 2°C and to strive for warming of no more than 1.5°C.

Warming beyond that lower threshold threatens to destroy the world’s coral reefs, trigger unstoppable melting of polar ice sheets and condemn small island nations to rising sea levels.

A single year of warming beyond 1.5°C wouldn’t constitute an official breach of the Paris target. That would only happen if the temperature rise was sustained over a couple of decades.

But it would be a clear, concerning signal that the world is on course to overshoot the temperature goal, said at the Met Office in a briefing with reporters.

“We really are now within reach of a temporary exceedance of 1.5°C for the annual mean. That is the first time in human history we have been that close,” he said. “It shows we are getting very, very close to the Paris threshold.”

The chance of temporarily exceeding 1.5°C in the short term has been rising steadily since 2015, when the probability was put at close to zero. By 2022, the Met Office suggested there was a “50-50” chance one of the five years from 2022 to 2026 would see warming exceed 1.5°C.

Rising greenhouse gas emissions and an expected shift to an El Niño weather pattern later this year mean a 1.5°C overshoot is now even more likely, the Met Office said.

El Niño and La Niña are terms used to describe fluctuations in Earth’s climate system, driven by changing sea surface temperatures in the equatorial Pacific.

After three years of La Niña, which has a cooling effect on global temperatures, earlier this month the US National Oceanic and Atmospheric Administration said there is a 90 per cent chance El Niño conditions will develop by the end of the year.

A strong El Niño could temporarily raise the global average temperature by 0.3°C, in addition to the warming already caused by greenhouse gas emissions.

“A warming El Niño is expected to develop in the coming months and this will combine with human-induced climate change to push global temperatures into uncharted territory,” said WMO secretary-general Petteri Taalas in a statement.

Even if temperatures don’t exceed the 1.5°C threshold, it is almost certain the world will experience record warmth in the next five years.

The current warmest year we have seen is 2016, when average temperatures were 1.28°C above pre-industrial levels. There is a 98 per cent chance this record will be broken by the end of 2027, the Met Office said.