There is a 66-per-cent likelihood that the annual average near-surface global temperature between 2023 and 2027 will be more than 1.5°C above pre-industrial levels for at least one year. There is also a 98-per-cent likelihood that at least one of the next five years, and the five-year period as a whole, will be the warmest on record.

A warming El Niño and human-induced climate change is expected to push global temperatures into uncharted territory, noted WMO secretary-general Prof. Petteri Taalas. “This will have far-reaching repercussions for health, food security, water management and the environment. We need to be prepared,” he said.

He added that while the UN agency’s analysis doesn’t mean the world will permanently exceed the 1.5°C level specified in the Paris Agreement, which refers to long-term warming over many years, the report nevertheless sounds the alarm that “we will breach the 1.5°C level on a temporary basis with increasing frequency”.

There is only a 32-per-cent chance that the five-year mean will exceed the 1.5°C threshold, according to the Global Annual to Decadal Climate Update produced by the UK’s Met Office, the WMO lead centre for such predictions. The chance of temporarily exceeding 1.5°C has risen steadily since 2015, when it was close to zero. For the years between 2017 and 2021, there was a 10-per-cent chance of surpassing the temperature limit.

“Global mean temperatures are predicted to continue increasing, moving us away further and further away from the climate we are used to,” said Met Office expert scientist Dr Leon Hermanson, who led the report.

Last year, the average global temperature was about 1.15°C above the 1850-1900 average. The cooling influence of La Niña conditions over much of the past three years temporarily reined in the longer-term warming trend. But La Niña ended in March this year and an El Niño is forecast to develop in the coming months. Typically, El Niño increases global temperatures in the year after it develops.

Arctic warming and changes in rainfall expected

The annual mean global near-surface temperature for each year between 2023 and 2027 is predicted to be between 1.1°C and 1.8°C higher than the 1850-1900 average. This is used as a baseline because it was before the emission of greenhouse gases from human and industrial activities.

Worryingly, arctic warming is expected to be disproportionately high. Compared with the 1991-2020 average, the temperature anomaly for the region is predicted to be more than three times as large as the global mean anomaly when averaged over the next five northern hemisphere extended winters.

Predicted precipitation patterns for the May-to-September 2023-2027 average, compared with the 1991-2020 average, suggest increased rainfall in the Sahel, northern Europe, Alaska and northern Siberia, and reduced rainfall in these months over the Amazon and parts of Australia.

Climate adaptation to be discussed

In addition to increasing global temperatures, human-induced greenhouse gases are leading to more ocean heating and acidification, sea ice and glacier melt, rising sea levels, and more extreme weather.

The Paris Agreement sets long-term goals to guide all nations to substantially reduce global greenhouse gas emissions to limit the global temperature increase in this century to 2°C, while also pursuing efforts to limit the increase even further to 1.5°C, to avoid or reduce adverse impacts and related losses and damages. According to the Intergovernmental Panel on Climate Change, climate-related risks for natural and human systems are higher for global warming of 1.5°C than at present, but lower than at 2°C.

The new report was released ahead of the World Meteorological Congress, which runs from 22 May to 2 June. The meeting will discuss how to strengthen weather and climate services to support climate change adaptation. Priorities for discussion at the Congress include the ongoing Early Warnings for All initiative to protect people from increasingly extreme weather, and a new Greenhouse Gas Monitoring Infrastructure to inform climate mitigation.