How climate change is slowing down time and why that’s a good thing (for now)

It was Einstein who originally said that time is relative, an idiom since happily repeated by the most condescending of amateur physicists. Yet, a research paper published in the scientific journal Nature has proposed that time might actually be slowing down – or at least, the way in which we measure it is. And it’s all down to global warming.

This isn’t just talking about how a hot summer’s day can seem to drag on forever, although, there’ll probably be more of that. Rather, as with so many aspects of climate change, the effects are being felt through the melting of the polar ice caps. The theory, as advanced by Professor Duncan Agnew of the University of California San Diego, is that the melting polar ice gathers around the equator, and that this is reaching such a scale as to actually slightly alter the shape of the Earth.

“This is another one of those ‘this has never happened before’ things that we’re seeing from global warming”

–Professor Agnew

Over time, this change has had an effect similar to how a figure-skater will extend their arms in order to slow down a pirouette: it has managed to slow down the Earth’s rotation. It’s yet another reminder of the sheer scale of the changes humankind is inflicting on the planet. As Professor Agnew cheerfully told Scientific American, “This is another one of those ‘this has never happened before’ things that we’re seeing from global warming: the idea that this effect is large enough to change the rotation of the entire Earth.”

So, an imminent catastrophe for humanity then (besides all the other effects of global warming)? Perhaps we’re doomed to live our lives in slow-motion, watching Netflix on 2x speed? Well, no. It should go without saying that whilst the slowing of the Earth’s rotation would make our days longer, it won’t actually affect our perception of time. What’s more, the actual phenomenon of Earth’s rotation slowing isn’t new, even if the exact reasons for it are. Earth has in fact been slowing down for thousands of years, as Professor Agnew notes in his paper, largely because of the relationship between the Earth, its oceans, and the Moon.

For 55 years, scientists have instead defaulted to a measure of timekeeping far more reliable than something so fickle as the movement of the planet. The atomic clock works by measuring the wave frequency of, well, atoms. It is supremely accurate, to the point that it and traditional astronomical time diverged almost immediately, to the tune of 2.5 milliseconds every (astronomical) day. To account for the discrepancy, scientists would periodically introduce a leap second onto the end of a day, appearing on clocks as 23:59:60. Since 1972, we have been given 27 bonus seconds – long enough to enjoy a good piece of art. So as far as the days passing a bit more slowly goes, its nothing scientists haven’t been dealing with already.

Indeed, could there be a silver lining to climate change slowing the Earth’s rotation? In a sense, yes, and here’s where it does get a lot more complex, because what hasn’t been discussed until now is that, broadly speaking, the Earth isn’t even slowing down – its speeding up.

This poses an entirely new challenge for the guardians of global timekeeping

The reason for this still isn’t fully clear yet. As recently as last year, some astronomers speculated that climate change was actually speeding up the Earth, not slowing it down, by smoothing the shape of the planet from a slightly lopsided sphere to something more circular, allowing it to spin faster. In his paper, Professor Agnew has now argued the reason lies with shifts in the behaviour of the Earth’s core, “a large ball of molten fluid” that he says has shortened the length of a day by about 0.0025 seconds over the last fifty years. It’s meant that, where historically the Earth has been slowing down, that deceleration stabilised around 2017, and since then, very slightly, the Earth has begun to instead speed up.

This poses an entirely new challenge for the guardians of global timekeeping – where they boast plenty of experience in adding time, they have never before had to take it away, and it doesn’t immediately appear as though that’s something computers can really do. The not-so-simple act of ending the day on 23:59:59 could trigger a raft of software issues akin to Y2K. Differences in software on the satellites of various countries may actually make such a change impossible, raising the prospect that parts of the world permanently slip a second out-of-sync with each other.

This metronomic migraine was due to hit as early as 2026. But introduce the melting polar icecaps, and Professor Agnew now reckons the dampening effects of climate change have delayed the issue until at least 2029. It’s fitting, in a way – our constant putting-off of confronting global warming has finally been rewarded in-kind, allowing us to put any concerns over an accelerating Earth to the back of our minds for at least another half-decade.