Global temperatures are set to reach a new record high in the next five years and have a greater than even chance of temporarily exceeding a rise of more than 1.5C for the first time in human history, the World Meteorological Organization concludes in its latest annual assessment.
In their stark conclusion, scientists said for the first time there was a 66 per cent chance that the annual mean global surface temperature rise would temporarily exceed 1.5C and reach as high as 1.8C above pre-industrial levels in “at least” one year by 2027.
The chances were “increasing with time”, said the report. The 66 per cent assessment of a temporarily breach of the 1.5C threshold compares with estimates of around 48 per cent a year ago, and “close to zero” in 2015.
The report, compiled by researchers from 11 organisations around the world, including those in Europe, North America, Japan and China, covers the years 2023 to 2027.
The authors said there was a 98 per cent chance that one of the five years would exceed the record high temperature rise of 1.28C touched in 2016, and that the next half-decade as a whole would be the warmest on record.
The return of the El Niño weather phenomenon in the Pacific Ocean was expected by the end of this year, which typically increases global temperatures.
Arctic temperatures were expected to rise more than three times faster than the global average, as melting of the snow and ice reduces the ability to reflect back the sun and causes greater warming than elsewhere.
“We are now within reach of a temperature exceedance of 1.5C . . . that’s the first time in human history we’ve been that close,” said Adam Scaife, head of monthly to decadal prediction at the UK’s Met Office Hadley Centre.
Many of the forecasts for the El Niño phenomenon “that we think is developing this winter are showing a pretty big amplitude El Niño”, he added.
The hottest year on record in 2016 occurred during an “exceptionally strong” El Niño event.
The opposing weather phenomenon, La Niña, has persisted for three years, and typically has a cooling effect. Despite that, the eight years from 2015 were likely to have been the warmest stretch on record, according to the WMO’s assessment.
Global temperatures have risen at least 1.1C already on an average long-term basis. The Paris Agreement commits nations worldwide to limit the average rise in temperatures over the long term to 1.5C, ideally — which is a different measure to the average increase in a given year. Scientists forecast that irreversible changes to the planet will occur beyond that level of warming.
Over the next five years, the researchers forecast that warming in the Arctic would be “disproportionately high”. The melting of sea ice could mean more shipping lanes opening up, said Leon Hermanson, a senior scientist at the Met Office Hadley Centre.
As the planet warms, high latitude areas in the northern hemisphere, such as Scandinavia and Siberia, were expected to experience above average rainfall between November and March over the next five years, the scientists said.
Between May and September, meanwhile, rainfall was expected to be above the 1991 to 2020 average in the Sahel region of Africa, northern Europe, Alaska and northern Siberia, but below average in the Amazon and parts of Australia.
These were all conditions “consistent with the climate warming”.
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