For the first time ever, global temperatures are now more likely than not to breach 1.5°C (2.7°F) of warming within the next five years, the World Meteorological Organization said on May 17.
But that did not necessarily mean the world would cross the long-term warming threshold of 1.5°C above preindustrial levels set out in the 2015 Paris Agreement.
With a 66% chance of temporarily reaching 1.5°C by 2027, "it's the first time in history that it's more likely than not that we will exceed 1.5°C," said Adam Scaife, head of long-range prediction at Britain's Met Office Hadley Centre who worked on the WMO's latest Global Annual to Decadal Climate Update.
Last year's report put the odds at about 50-50.
Partially responsible for boosting the chance of hitting 1.5°C is an El Nino weather pattern expected to develop in the coming months. During this natural phenomenon, warmer waters in the tropical Pacific heat the atmosphere above, spiking global temperatures.
The El Nino "will combine with human-induced climate change to push global temperatures into uncharted territory", said WMO Secretary-General Petteri Taalas in a press statement.
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Still, the likelihood of temporarily exceeding 1.5°C has increased over time. Between 2017 and 2021, for example, scientists estimated just a 10% chance of hitting 1.5C.
Unlike the U.N. Intergovernmental Panel on Climate Change's climate projections which are based on future greenhouse gas emissions, the WMO update provides more of a prediction-based long-range weather forecast.
The WMO also found a 98% chance that one of the next five years will be the hottest on record, surpassing 2016 which saw global temperature impacted by about 1.3°C (2.3°F) of warming.
Next five years set to be hottest period ever: UN
It is near-certain that 2023-2027 will be the warmest five-year period ever recorded, the United Nations warned Wednesday as greenhouse gases and El Nino combine to send temperatures soaring.
There is a two-thirds chance that at least one of the next five years will see global temperatures exceed the more ambitious target set out in the Paris accords on limiting climate change, the UN’s World Meteorological Organization (WMO) said.
The hottest eight years ever recorded were all between 2015 and 2022, with 2016 the warmest — but temperatures are forecast to increase further as climate change accelerates
“There is a 98-percent likelihood that at least one of the next five years, and the five-year period as a whole, will be the warmest on record,” the WMO said.
The 2015 Paris Agreement saw countries agree to cap global warming at “well below” two degrees Celsius above average levels measured between 1850 and 1900 — and 1.5°C if possible.
The global mean temperature in 2022 was 1.15°C above the 1850-1900 average.