How is climate change slowing Earth's rotation?
Rising seas and shifting mass lengthen our days
Earth’s rotation is getting imperceptibly slower as water and other mass move across the planet. Scientists have shown that the redistribution of mass—principally from melting ice and rising sea levels—pushes mass farther from Earth’s axis. Conservation of angular momentum then causes the planet’s rotation to slow slightly, making each day a tiny bit longer.
Recent analyses indicate that the current rate of change is unusual in a geological context: the present increase in day length tied to sea-level rise appears to be unprecedented when compared with records stretching back millions of years. That makes the phenomenon a measurable geophysical fingerprint of modern climate change.
Key mechanics and consequences
- Mass redistribution: melting land ice and thermal expansion move water into the oceans and toward higher latitudes, altering the planet’s moment of inertia.
- Rotation change: as the moment of inertia increases, rotation slows a small amount, lengthening the mean solar day by fractions of a second.
- Practical effects: the changes are extremely small for daily life but matter for precision systems—atomic timekeeping, satellite navigation, and long-term geophysical records.
What comes next
- Timekeeping agencies track these tiny shifts and occasionally add leap seconds to keep civil time aligned with Earth's rotation. Faster sea-level rise could increase the frequency of such adjustments.
- Scientific value: the signal offers another independent line of evidence linking contemporary warming, sea-level rise, and global mass redistribution.
Uncertainties remain about how the trend will evolve because future rates depend on how much ice melts and how ocean mass redistributes. The finding underscores that climate change is not only an atmospheric and ecological problem but one that subtly reshapes Earth’s physical dynamics.