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Human-caused climate change has ‘slowed the Earth’s rotation’ and could affect how we measure time, study suggests


Melting polar ice due to human-caused climate change has slightly slowed the Earth’s rotation – and it could affect the way we measure time, a study suggests.

Even though the disappearance of the ice has reduced the planet’s rotation speed, the Earth still rotates a little faster than before.

The overall increase in speed means that, for the first time in history, the world’s timekeepers may have to consider subtracting a second from our clocks.

That means clocks may need to jump a second – called a “negative leap second” – around 2029 to keep universal time in sync with Earth’s rotation, according to the study published in the journal Nature.

Without the impact of melting ice, the time change would have been necessary three years earlier, in 2026.

In recent decades, Earth has been spinning faster due to changes in its core, but melting ice has thwarted this acceleration.

Icebergs and melting ice floes in Greenland.  Photo: AP
Icebergs and melting ice floes in Greenland. Photo: AP

The world rotation is like a figure skater twirling

Duncan Agnew, study author and geophysicist at the Scripps Institution of Oceanography at the University of California, says melting ice in Greenland and Antarctica has changed where land mass is concentrated.

This has slowed Earth’s rotation, because less solid ice in the northern and southern areas of the planet means there is more mass around the equator, the study suggests.

Mr. Agnew used the example of a figure skater twirling on the ice to explain this.

He told Sky News’ US partner network NBC News: “If you have a skater who starts to turn, if she lowers her arms or stretches her legs, she will slow down.”

However, if a skater’s arms are pulled inward, it means she will turn faster.

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Melting ice in Greenland and Antarctica is an accelerating trend believed to be primarily due to human-caused climate change.

This means that humans could make the Earth rotate less quickly than it would otherwise.

Mr. Agnew continued: “It’s pretty impressive, even to me, that we’ve done something that measurably changes the speed of the Earth’s rotation.

“Unprecedented things are happening.”

The melting of polar ice would be a new factor affecting the rotation of the Earth.

Friction from ocean tides, due in part to the Moon’s gravitational pull, slows the Earth’s rotation.

Meanwhile, the movement of fluids in Earth’s liquid inner core can either speed up or slow down the planet’s rotation speed, Agnew said.


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