We’ve just had the 11 hottest years on record

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The years from 2015 to 2025 have been the hottest stretch on record, according to a report by the World Meteorological Organization. For the first time, the report includes a measure called Earth’s energy imbalance — the difference between incoming energy from the Sun and the amount radiated back into space — which is at its highest level since observations started in 1960. And in 2024, the latest year that global figures are available, atmospheric CO₂ reached its highest concentration in two million years.

“In this age of war, climate stress is also exposing another truth: our addiction to fossil fuels is destabilizing both the climate and global security,” said United Nations Secretary-General António Guterres in a statement.

Nature | 5 min read

Reference: State of the Global Climate 2025 report

Researchers have used stem cells to make bioengineered oesophagi. Segments of these lab-grown organs were successfully transplanted into pigs to restore the animals’ ability to swallow and eat. The team say that similar structures might be used to treat children born with a large hole in their oesophagus, or adults whose throat muscles have been damaged by cancer. Compared to existing treatments, “it would be a much less invasive procedure if we could make it work”, says surgeon Andrew Barbour.

Nature | 4 min read

Reference: Nature Biotechnology paper

After decades of research, physicists are confident that the first tick of a ‘nuclear clock’ is imminent. This device would keep time by measuring energy transitions in the radioactive isotope thorium-229, which could make it the most precise clock on the planet. Last week, scientists at the American Physical Society Global Physics Summit compared notes on their progress toward assembling the clock’s components, including efforts to build a laser that can make the clock ‘tick’. “You’ll see nuclear-clock measurements in 2026, I’m sure,” says physicist Eric Hudson.

Nature | 6 min read

Features & opinion

In The AI Illusion, computer scientist Luc Julia argues that the hype and fear surrounding the intelligence and creative abilities of artificial intelligence models are overblown. “Just as a magician uses sleight of hand to create the illusion of magic, the terminology around AI creates the illusion of human-like intelligence,” he tells Nature. AI ‘intelligence’ often refers to a system’s information-processing abilities, rather than any real cognitive ability, he says. “The reality is that AI is a tool created by humans, for humans, and its capabilities are defined by the parameters we set.”

Nature | 8 min read

Gross domestic product (GDP) doesn’t reflect the rapidly changing structure of modern economies and has a narrow focus: it only counts what can be bought and sold. But there are other ways to measure what makes for a good life. “For example, a tree’s sequestration of carbon and release of oxygen are not recorded in GDP, even though they have or create value to people,” write economists Richard Heys and Himanshi Bhardwaj, and statistician Cliodhna Taylor. They report on a UK Office for National Statistics project to explore how to provide a more holistic view of economic prosperity.

Nature | 15 min read

Image of the week

Maybe Captain Ahab was on to something: sperm whales (Physeter macrocephalus) really do ram things with their heads. Researchers used a drone to film youngsters in the Azores and Balearic archipelagos headbutting each other, and gathered mentions of such behaviour in other studies. “It was really exciting to observe this behaviour, which we knew had been hypothesised for such a long time, but not yet documented and described systematically,” says biologist Alec Burslem. “If there are people out there with similar footage, we would be very keen to hear from them.” (Popular Science | 5 min read)

Reference: Marine Mammal Science paper (Association Tursiops)

On Friday, Leif Penguinson was investigating lines of glacial crevasses on Mount Tronador in Argentina. Did you find the penguin? When you’re ready, here’s the answer.

Thanks for reading,

Flora Graham, senior editor, Nature Briefing

With contributions by Jacob Smith

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