Time is slowing down because of melting polar ice
Next time you’re late for work, feel free to blame climate change.
A study published yesterday has suggested planet-warming fossil fuels are slowing down time by rapidly melting the polar ice caps.
Well, kind of. The Earth is basically one big clock – the planet spins around and you see the sun rise and set roughly every 24 hours.
Rough is the key word here. Astronomical time can be off by a fraction of a second because of activity on the Earth’s surface, its quick-tempered molten core, the sun and the moon.
The Earth’s rotation has recently begun speeding up after slowing down for millions of years because of its core.
But the University of California study suggests climate change is actually slowing down how quickly the Earth is rotating – the speed is still picking up, just not as quickly as it could be.
The two together mean that for the first time ever, we will lose a second in 2029. Without the effects of melting ice, this would have happened three years earlier, the study published in Nature found.
Felicitas Arias, former director of the Time Department at the International Bureau of Weights and Measures in Sèvres, France, wrote in an accompanying article: ‘We do not know how to cope with one-second missing.
‘This is why time metrologists are worried.’
For millions of years, the Earth’s rotation has gradually slowed because of the moon’s pull over the tides, said Duncan Agnew, professor of geophysics at the University of California San Diego and the study’s author.
About 70 million years ago, for example, a day lasted roughly 23.5 hours, a study in Paleoceanography and Paleoclimatology found.
This wasn’t much of an issue until 1969 when scientists introduced super-precise atomic time, also called Coordinated Universal Time (UTC), to act as the official time standard.
While UTC never changes – it is based on 450 atomic clocks, after all – the Earth’s slowing rotation meant astronomical time was a tiny bit behind it.
Timekeeping is a seriously precise science. So timekeepers have been adding ‘leap seconds’ to bridge the gap between these two time standards.
Lots of different things impact how long it takes the planet to rotate – and sometimes they can counteract one another, which is what Californian scientists found.
Agnew said that the Earth’s core has been triggering a speedup for the last 50 years and a day has become about 0.0025 seconds shorter. The shortest day in recorded history was June 22 2022, when the day was 1.59 milliseconds shorter.
As David Armstrong, and associate professor at the University of Warwick, explained to Metro.co.uk: ‘The length of a day is the time it takes the Earth to rotate once. If the Earth is speeding up, then the days are getting very, very slightly shorter.’
Yet the melting polar ice in Greenland, Antarctica, Alaska and Patagonia has slowed that slightly.
But none of this means that time is being ‘messed with’, stresses Dr James Davis, Lamont Research Professor at the Lamont-Doherty Earth Observatory of Columbia University.
Agnew’s paper, he said, ‘focuses on how we keep time, that is, how we keep track of time’.
Sadly, this means time itself isn’t slowing down. So you aren’t ageing slower.
‘We won’t age any differently or perceive time any differently because this is not the issue,’ Davis said.
Why the ice melting is slowing down the Earth’s rotational speed can be explained by thinking of an ice skater spinning in a rink.
‘Ice skaters increase the rate of their spin by moving their arms close to their body,’ Davis said.
This same is happening with all that water from the melting ice increasing sea levels and pooling around the Equator – the planet’s love handles. ‘It’s as though Earth were extending its arms and that causes Earth’s rate of rotation to tend to slow,’ Davis said.
‘You can try the same thing in a chair or stool that swivels,’ Davis adds, ‘although please use caution.’
As Professor Jonathan Bamber, of the University of Bristol’s School of Geographical Sciences, put it: ‘The Earth is like a gyroscope spinning on an axis.
‘If you move mass from one place to another on the surface (which is what happens when land ice melts and enters the ocean) to conserve angular momentum, the axis of rotation changes which affects the length of the day and this in turn influences timekeeping.’
Nevertheless, how climate change is now impacting the way we measure time itself should serve as a reminder rising temperatures are something to worry about, Agnew said.
‘I’ve been around climate change for a long time, and I can worry about it plenty well without this,’ he said, ‘but it’s yet another way of impressing upon people just how big a deal this is.’
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