The size of the jump in temperatures in 2023 surprised many scientists – sparking speculation about what might be behind the surge, in addition to carbon emissions and El Niño.
Theories include changes to clouds and tiny particles called aerosols, which appear to be reflecting less of the Sun’s energy back into space.
The persistence of extreme warmth into 2025 “suggests that there might be some mysteries that we haven’t fully solved”, said Hausfather.
“We are seeing rapid warming at the upper end of our longer-term expectations,” agreed Sutton.
But whether the last three years have significiant implications for the longer term “is not yet clear”, he added, with more data needed before making firm conclusions.
While scientists expect more records to be broken in the years ahead, they emphasise that the future impacts of climate change are not set in stone.
“We can strongly affect what happens,” said Sutton, “both by mitigating climate change – that’s by cutting greenhouse gas emissions to stabilise warming – and of course also by adapting, by making society more resilient to ongoing changes.”