There is a 50 per cent chance of the annual average global temperature temporarily reaching 1.5°C above pre-industrial levels for at least one of the next five years, the World Meteorological Organisation said on Tuesday.
The WMO's climate update said that the likelihood of the threshold being temporarily exceeded is increasing with time, and forecast a 93 per cent chance of at least one year between 2022-2026 succeeding 2016 as the warmest on record.
The annual update uses the expertise of internationally recognised climate scientists and the best prediction systems from leading climate centres around the world to produce actionable information for decision-makers.
The chance of temporarily exceeding 1.5°C has risen steadily since 2015, when it was close to zero.
Between 2017 and 2021, there was a 10 per cent chance — a probability that has increased to nearly 50 per cent for the 2022-2026 period.
“This study shows — with a high level of scientific skill — that we are getting measurably closer to temporarily reaching the lower target of the Paris Agreement on Climate Change,” said WMO Secretary General Petteri Taalas.
“The 1.5°C figure is not some random statistic. It is rather an indicator of the point at which climate impacts will become increasingly harmful for people and indeed the entire planet.
“For as long as we continue to emit greenhouse gases, temperatures will continue to rise. And alongside that, our oceans will continue to become warmer and more acidic, sea ice and glaciers will continue to melt, sea levels will continue to rise and our weather will become more extreme.
“Arctic warming is disproportionately high and what happens in the Arctic affects all of us,” said Mr Taalas.
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The Paris Agreement set long-term goals to guide all nations towards substantially reduce greenhouse gas emissions to limit the global temperature increase in this century to 2°C, while pursuing efforts to limit the increase even further to 1.5 °C.
The Intergovernmental Panel on Climate Change said climate-related risks for natural and human systems are higher for global warming of 1.5 °C, but lower than at 2 °C.
“Our latest climate predictions show that continued global temperature rise will continue, with an even chance that one of the years between 2022 and 2026 will exceed 1.5 °C above pre-industrial levels,” said Dr Leon Hermanson, of the Met Office, who led the report.
“A single year of exceedance above 1.5 °C does not mean we have breached the iconic threshold of the Paris Agreement, but it does reveal that we are edging ever closer to a situation where 1.5 °C could be exceeded for an extended period,” he said.
In 2021, the global average temperature was 1.1 °C above the pre-industrial baseline, the provisional WMO report on the State of the Global Climate said.
The final State of the Global Climate report for 2021 will be released on May 18.
Back-to-back La Nina events at the start and end of 2021 had a cooling effect on global temperatures, but this is only temporary and does not reverse the long-term global warming trend.
Any development of an El Nino event would immediately fuel temperatures, as it did in 2016, the warmest year on record.