The 1.5C threshold is measured in decades, not individual years, but Copernicus said reaching this limit even briefly illustrated the unprecedented changes being brought about by humanity.

Scientists say every fraction of a degree above 1.5C is consequential, and that beyond a certain point the climate could shift in ways that are difficult to anticipate.

At present levels, human-driven climate change is already making droughts, storms, floods and heatwaves more frequent and intense.

The death of 1,300 pilgrims in Saudi Arabia from extreme heat, a barrage of powerful tropical storms in Asia and North America, and historic flooding in Europe and Africa marked grim milestones in 2024.

The oceans, a crucial climate regulator which absorb 90 percent of excess heat from greenhouse gases, warmed to record levels in 2024, straining coral reefs and marine life and stirring violent weather.

Warmer seas mean higher evaporation and greater moisture in the atmosphere, causing heavier rainfall, feeding energy into cyclones and bringing sometimes unbearable humidity.

Water vapour in the atmosphere hit fresh highs in 2024 and combined with elevated temperatures caused floods, heatwaves and “misery for millions of people”, Burgess said.

‘Stark warning’

Johan Rockstrom of the Potsdam Institute for Climate Impact Research said hitting 1.5C was a “stark warning sign”.

“We have now experienced the first taste of a 1.5C world, which has cost people and the global economy unprecedented suffering and economic costs,” he told AFP.

Scientists say the onset of a warming El Nino phenomenon in 2023 contributed to the record heat that followed.

But El Nino ended in early 2024, and scientists have puzzled over why global temperatures have remained at record or near-record levels ever since.

In December, the World Meteorological Organization said if an opposite La Nina event took over in coming months it would be too “weak and short-lived” to have much of a cooling effect.

“The future is in our hands — swift and decisive action can still alter the trajectory of our future climate,” said Copernicus climate director Carlo Buontempo.

Nations agreed to transition away from fossil fuels at a UN summit in 2023 but the latest meeting in November struggled to make any progress around how to make deeper reductions to heat-trapping emissions.

© 2025 AFP