Due to climate change, the earth spins on its axis measurably less quickly, with consequences for global timekeeping

Due to the melting of the ice caps as a result of climate change, more and more meltwater is sinking towards the equator, where it bulges out very slightly as seen from space. The net effect is comparable to a skater turning pirouettes and extending his arms: the planet slows down just a little bit because of that bulging water.

That is more than a remarkable drinks fact. After all: the slower the Earth rotates, the longer astronomically speaking a ‘day’ lasts. And that affects the position of our universal clock, the global standard on which all time zones are based: ‘UTC’. American geophysicist Duncan Agnew wrote this on Wednesday in a professional article in a scientific journal Nature.

“UTC is maintained by the International Bureau of Weights and Measures in Paris, by averaging the time of more than four hundred atomic clocks,” says time manager Erik Dierikx of the national metrological institute VSL in Delft, where four of those atomic clocks are located. One of his tasks: checking when international bodies such as the IERS (International Earth Rotation Reference Systems Service) report that UTC is starting to deviate too much from astronomical time.

Not 24 hours

In practice, many more effects than the melting of the Arctic ice contribute to the fact that, astronomically speaking, a day never contains exactly 24 hours. Consider, among other things, the blowing of the wind, the friction between oceans and the earth’s crust, and the movement of the earth’s core.

To prevent the earthly clock from getting too out of sync with the cosmic clock, an extra second has been regularly added to a year in recent decades, a so-called leap second. In the meantime, despite the braking effect of the melting ice, the Earth has started to rotate faster and faster. As a result, the opposite will soon be necessary: ​​a negative leap second, a year in which a second disappears from the clock.

The slowing down by the meltwater does mean that that moment now takes place a little later than usual. Without climate change, the world would already need a negative leap second in 2025 or 2026. However, Agnew now estimates the arrival of the negative leap second at 2029.

“A very interesting study,” says Dierikx, who only questions that specific year. “This is a small effect,” he says. It is difficult to determine exactly how this will affect the actual duration of all days measured by IERS between now and 2029. “So I take 2029 with a grain of salt.”

Risks

But still: as far as he is concerned, any delay is good news, a blessing in disguise of human climate change. “It was decided last year that we will increase the threshold for introducing a leap second from 2035,” he says. There is always a risk that one computer system adopts the entered leap second, while another does not, after which both systems suddenly no longer communicate properly. This poses increasing risks in a world chock full of devices that use time: from internet connections to registrations of banking transactions and the positioning of GPS satellites.

With a negative leap second, something that has never been introduced before in human history, those risks are automatically even greater. Fortunately, says Dierikx, when the time comes, IERS will notify him six months in advance. “We can practice some more then.”