Why global warming is messing up our clocks

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Climate change is apparently upsetting more than just the climate itself. According to a new study, the melting of polar ice is causing the Earth’s rotation to slow down. This is having an impact on our chronology.

Shift second for customisation
Since 1972, a so-called leap second has been used to harmonise the time measured by atomic clocks with the speed of the Earth. According to the researchers, the next leap second will be delayed by three years due to climate change.

“So much ice has melted and sea levels have risen as a result that the speed of the Earth’s rotation has been affected,” geophysicist Duncan Agnew told Nature. According to the scientists’ calculations, the rise in sea levels will lead to the next required leap second being postponed from 2026 to 2029.

Since 1967, time has no longer been determined by the Earth’s rotation but by more accurate atomic clocks. These utilise the natural oscillation frequency of atoms to measure time precisely. A total of 450 atomic clocks tell us the official time today. The leap second, in turn, serves to synchronise the time calculation of the atomic clocks with the Earth’s rotation. This is because the Earth’s rotation is also influenced by what happens on the surface and inside our planet.

Threats computer systems
The leap second is not without controversy – computer scientists repeatedly argue in favour of its abolition because the leap second messes up computer systems.

Currently, people are particularly worried about the next leap second because, for the first time in history, it is likely to be a negative, skipped second instead of an additional one. Because it is a novelty, time calculation experts do not know how best to deal with it. For them, the news of the delay caused by climate change is therefore not inconvenient, as it could push back the negative leap second.
Researcher Ted Scambos describes the slowdown caused by the melting of the polar ice caps as if a figure skater were spinning with his arms above his head. When he brings his arms down to his shoulders, the rotation slows down.

Accelerating effect
However, it is not only the slowdown caused by the melting of the polar ice caps that need to be taken into account but also the simultaneous acceleration of the Earth’s rotation due to processes in the Earth’s interior. “The changes in the Earth’s core now tend to be greater than the ice loss at the poles – even though ice loss has increased in the last decade,” Scambos told CNN. For him, however, the Nature study shows that humans do have a significant impact on the Earth and could even influence the passage of time.