World may have entered era of 1.5C warming: Scientists

Last year's record-breaking temperatures could be a sign that the world is entering a new era above 1.5C of global warming, scientists say, one never before faced by modern humans.

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The Paris Agreement threshold of 1.5 degrees Celsius above preindustrial levels is a small-sounding number with big implications for people and nature.

It is a marker of risk, with more warming from planet-heating emissions linked to worsening floods, heatwaves and storms, as well as gradual effects like sea level rise and species extinctions.

"Every fraction of a degree beyond this level translates into more extreme weather, biodiversity loss, and human suffering," said William Ripple, Professor at Oregon State University.

But when can we say 1.5C is officially crossed? That is the focus of two studies published Monday in the journal Nature Climate Change.

Scientists sought to square the long-term Paris goals with the extraordinary heat seen in 2024, the first full calendar year above 1.5C, according to the World Meteorological Organisation.

A single year above the limit does not mark a breach of the Paris deal, which is measured as a rolling average over 20 or 30 years, to smooth out year-on-year temperature variability.

By that measure the world has so far warmed roughly 1.3C, warmer than it has been for the last 125,000 years, scientists say.