<p>The only answer I can come up with is related to <a href="https://sealevel.colorado.edu/presentation/what-glacial-isostatic-adjustment-gia-and-why-do-you-correct-it" rel="nofollow noreferrer">isostasy</a>.</p>
<p>1 - Poles melt, so there's more water in the oceans.
2 - As there's more water in the oceans, there's more weight on the oceanic crusts, so they bend, <a href="https://sealevel.colorado.edu/presentation/what-glacial-isostatic-adjustment-gia-and-why-do-you-correct-it" rel="nofollow noreferrer">making deeper some parts of the oceans.</a>
3 - The parts of the ocean that are deeper are in the centre of the oceans, far from continental crust. It should be mainly the Pacific Ocean, Indic and Atlantic, but not near Antarctica, as this area is continental crust (lighter) and will be also unloaded from ice.
4 - As a result, the shape of the Earth crust becomes a bit longer in N-S direction.
5 - As the mass of the Earth is closer to the rotation axis, it accelerates the spin.</p>
<p>Lithospheric density is <a href="https://en.wikipedia.org/wiki/Isostasy" rel="nofollow noreferrer">approximately 2.5 times that of water</a>, so amount of water in the ocean isn't as important as crust flexion.</p>

CC BY-SA 4.0
2021-01-11T23:23:31.727Z
Thanks for the edit!
uhoh
CC BY-SA 4.0
2021-01-11T12:33:24.090Z
2021-01-11T23:10:38.467Z
2021-01-11T23:10:38.467Z
georostro
<p>This study seems to suggest that global warming will change oceanic circulation and transfer a net increase of mass to the poles, closer to the axis of rotation, therefore speeding up the spin.</p>
<p>article: <a href="https://www.newscientist.com/article/dn11555-global-warming-will-make-earth-spin-faster/" rel="nofollow noreferrer">https://www.newscientist.com/article/dn11555-global-warming-will-make-earth-spin-faster/</a>
study: <a href="https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006GL029106" rel="nofollow noreferrer">https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006GL029106</a></p>
<p>Much of this transfer of mass seems to be to do with water flooding low-lying areas in the northern hemisphere, and I assume that adding to this effect will be lower density frozen water being replaced by higher density liquid water around the poles.</p>

CC BY-SA 4.0
2021-01-17T04:03:23.870Z
This is a very specific and well-sourced answer, thank you! Looking at Figure 4 and accumulating 20 years of -0.01 ms/day to get to 2020 (which seems generous) I get to -0.07 seconds. In other words it's the right sign and we might *eventually* need a negative leap second (i.e. .`..56, 57, 58, 00, 01, 02...`) but it's not clear if *the next* leap second will be negative.
uhoh
CC BY-SA 4.0
2021-01-17T04:14:21.670Z
you may find the following interesting; (2nd one has a bounty) [Why doesn't Wolfram Alpha show low gravitational acceleration for the Hudson Bay?](https://earthscience.stackexchange.com/q/16787/6031) and [What would be the depth variation of a “water ellipsoid” above a reference ellipsoid Earth?](https://earthscience.stackexchange.com/q/12096/6031)
uhoh
CC BY-SA 4.0
2021-01-11T19:40:15.677Z
2021-01-11T19:53:39.333Z
2021-01-11T19:53:39.333Z
Amphibio
<p>I recently read a <a href="https://fanf.dreamwidth.org/133823.html?fbclid=IwAR1O5awjNok30m30PjbuoHuqhDIYTx1z2xcgHEDfzsKKZ85bTZuS1iNuTpg" rel="nofollow noreferrer">blog entry</a> from a leap-second expert explaining that in near term (i.e. last 3 years) the Earth has been spinning ever so slightly faster, delaying the need to insert a leap-second (that accounts for the Earth spinning at a different speed than once per 24 * 60 * 60 seconds).</p>
<p>That got me wondering what effect Climate Change might have had on the spin of the Earth over the last century, and into the next.</p>
<p>I reasoned that melting ice caps would bring mass closer to the centre, lowering the moment of inertia and speeding up the spin (which was a silly thought - see comments).</p>
<p>But then I reasoned that warming oceans would lower the density of water, pushing the mass away.</p>
<p>Then I realised I had no idea what effect of the changing atmosphere might have.</p>
<p>I came away knowing I had a very poor understanding of the problem.</p>
<p>What predictions do the scientific models make about the effect of climate change on the previous rate of gradual slowing of the Earth's spin?</p>
<p>[Note: This is an idle curiosity question from a non-expert. Please tailor your answering efforts appropriately.]</p>

CC BY-SA 4.0
2020-11-20T08:16:09.713Z
Don't know anymore than you, but thinking that the ice caps melting might actually move mass away from the axis of rotation because the Poles are along the axis of rotation, while if the water moves away from the Poles (even if it managed to be slightly closer to the center of Earth... which may not be true due to the oblate shape of the Earth), it'd be further from the axis?
JeopardyTempest
CC BY-SA 4.0
2020-11-20T08:37:29.327Z
@Jeopardy: Now that you say it, it is so obvious! DUH! Thanks.
Oddthinking
CC BY-SA 4.0
2020-11-20T09:17:29.370Z
Could you please add a link to said blog entry?
Jean-Marie Prival
CC BY-SA 4.0
2020-11-20T19:47:11.690Z
@Jean-MariePrival: I have added it, but *this is just background*. I am worried answers will address the claims about leap-seconds in the blog entry, which isn't the topic of my question.
Oddthinking
CC BY-SA 4.0
2020-11-21T20:15:40.917Z
Math done here: [Was the filling of the Three Gorges Dam's impact on the Earth's rotation rate detectable?](https://earthscience.stackexchange.com/a/15946/6535)
Keith McClary
CC BY-SA 4.0
2020-11-26T13:35:17.707Z
@tlb: And how does this compare to the effects of the [atmosphere](https://link.springer.com/article/10.1023/A:1014847319391z) and warmer oceans? It may well be trivial. Hence the question.
Oddthinking
CC BY-SA 4.0
2021-01-11T17:34:39.847Z
[Recent research](https://scholar.google.com/scholar?hl=en&as_sdt=2005&sciodt=0%2C5&cites=10152639842302384885&scipsc=&q=earth+rotation+sea+level&btnG=).
Keith McClary
<climate-change><planetary-science><earth-rotation>
What effect does climate change have on the Earth's rotation?
Oddthinking
# What effect does climate change have on the Earth's rotation?

(Asked by: username_0 on 2020-11-20)

I recently read a [blog entry](https://fanf.dreamwidth.org/133823.html?fbclid=IwAR1O5awjNok30m30PjbuoHuqhDIYTx1z2xcgHEDfzsKKZ85bTZuS1iNuTpg) from a leap-second expert explaining that in near term (i.e. last 3 years) the Earth has been spinning ever so slightly faster, delaying the need to insert a leap-second (that accounts for the Earth spinning at a different speed than once per 24 \* 60 \* 60 seconds).

That got me wondering what effect Climate Change might have had on the spin of the Earth over the last century, and into the next.

I reasoned that melting ice caps would bring mass closer to the centre, lowering the moment of inertia and speeding up the spin (which was a silly thought - see comments).

But then I reasoned that warming oceans would lower the density of water, pushing the mass away.

Then I realised I had no idea what effect of the changing atmosphere might have.

I came away knowing I had a very poor understanding of the problem.

What predictions do the scientific models make about the effect of climate change on the previous rate of gradual slowing of the Earth's spin?

[Note: This is an idle curiosity question from a non-expert. Please tailor your answering efforts appropriately.]

**Tags:** climate-change, planetary-science, earth-rotation

> **Comments:**
> **username_1**: Don't know anymore than you, but thinking that the ice caps melting might actually move mass away from the axis of rotation because the Poles are along the axis of rotation, while if the water moves away from the Poles (even if it managed to be slightly closer to the center of Earth... which may not be true due to the oblate shape of the Earth), it'd be further from the axis?  
> **username_0**: @Jeopardy: Now that you say it, it is so obvious! DUH! Thanks.  
> **username_2**: Could you please add a link to said blog entry?  
> **username_0**: @username_2: I have added it, but *this is just background*. I am worried answers will address the claims about leap-seconds in the blog entry, which isn't the topic of my question.  
> **username_3**: Math done here: [Was the filling of the Three Gorges Dam's impact on the Earth's rotation rate detectable?](https://earthscience.stackexchange.com/a/15946/6535)  
> **username_0**: @tlb: And how does this compare to the effects of the [atmosphere](https://link.springer.com/article/10.1023/A:1014847319391z) and warmer oceans? It may well be trivial. Hence the question.  
> **username_3**: [Recent research](https://scholar.google.com/scholar?hl=en&as_sdt=2005&sciodt=0%2C5&cites=10152639842302384885&scipsc=&q=earth+rotation+sea+level&btnG=).  

---

## 2 answers

### Answer by username_4 on 2021-01-11. Score: 3

The only answer I can come up with is related to [isostasy](https://sealevel.colorado.edu/presentation/what-glacial-isostatic-adjustment-gia-and-why-do-you-correct-it).

1 - Poles melt, so there's more water in the oceans.
2 - As there's more water in the oceans, there's more weight on the oceanic crusts, so they bend, [making deeper some parts of the oceans.](https://sealevel.colorado.edu/presentation/what-glacial-isostatic-adjustment-gia-and-why-do-you-correct-it)
3 - The parts of the ocean that are deeper are in the centre of the oceans, far from continental crust. It should be mainly the Pacific Ocean, Indic and Atlantic, but not near Antarctica, as this area is continental crust (lighter) and will be also unloaded from ice.
4 - As a result, the shape of the Earth crust becomes a bit longer in N-S direction.
5 - As the mass of the Earth is closer to the rotation axis, it accelerates the spin.

Lithospheric density is [approximately 2.5 times that of water](https://en.wikipedia.org/wiki/Isostasy), so amount of water in the ocean isn't as important as crust flexion.

> **Comments:**
> **username_5**: Thanks for the edit!  

---

### Answer by username_6 on 2021-01-11. Score: 2

This study seems to suggest that global warming will change oceanic circulation and transfer a net increase of mass to the poles, closer to the axis of rotation, therefore speeding up the spin.

article: <https://www.newscientist.com/article/dn11555-global-warming-will-make-earth-spin-faster/>
study: <https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006GL029106>

Much of this transfer of mass seems to be to do with water flooding low-lying areas in the northern hemisphere, and I assume that adding to this effect will be lower density frozen water being replaced by higher density liquid water around the poles.

> **Comments:**
> **username_5**: This is a very specific and well-sourced answer, thank you! Looking at Figure 4 and accumulating 20 years of -0.01 ms/day to get to 2020 (which seems generous) I get to -0.07 seconds. In other words it's the right sign and we might *eventually* need a negative leap second (i.e. .`..56, 57, 58, 00, 01, 02...`) but it's not clear if *the next* leap second will be negative.  
> **username_5**: you may find the following interesting; (2nd one has a bounty) [Why doesn't Wolfram Alpha show low gravitational acceleration for the Hudson Bay?](https://earthscience.stackexchange.com/q/16787/6031) and [What would be the depth variation of a “water ellipsoid” above a reference ellipsoid Earth?](https://earthscience.stackexchange.com/q/12096/6031)  

---

