If you’ve been feeling like the days are taking longer than usual lately, you may not be alone, according to scientists.
Researchers from ETH Zurich have discovered that climate change is causing the number of days on Earth to increase at an ‘unprecedented’ rate.
As polar ice in Greenland and Antarctica melts, the Earth’s center of gravity shifts toward the equator, gradually slowing the planet’s rotation.
If emissions levels aren’t reduced, the researchers predict this shift could add 2.62 milliseconds to the day by the end of 2100, a bigger impact than the moon.
While the effects are not noticeable to most people, researchers say the subtle changes could have major implications for space travel.
Scientists have discovered that Earth’s days are getting longer at an ‘unprecedented rate’ due to climate change
While it may seem strange that humans could influence something as inevitable as the passing of the day, the physics is actually quite simple.
As human-induced climate change raises the temperature of the world’s oceans, meltwater flows from the polar ice caps toward the equator.
Co-lead author Benedikt Soja from ETH Zurich explains: ‘It’s like a figure skater doing a pirouette: first she holds her arms close to her body and then extends them.
‘The initially fast rotation slows down because the masses move away from the rotation axis, increasing the physical inertia.’
As the Earth’s rotation slows, the time it takes to rotate on its axis increases, and the days become slightly longer than the standard 86,400 seconds.
This is not the only thing that can cause changes in the Earth’s rotation. The planet’s speed is also affected by the gravitational pull of the moon and the conditions in its inner layers.
As the polar ice in Antarctica (pictured) and Greenland melts, fresh water flows toward the equator, disrupting Earth’s balance and slowing the planet’s rotation.
However, in two recent papers, researchers have managed to distinguish the different effects of each of these factors.
For most of Earth’s history, the length of the day was most affected by “tidal friction,” caused by the Moon’s gravity pulling on the ocean.
Due to tidal friction, the day lengthens by about 2.4 milliseconds every century over millions of years.
Researchers estimate that the shift in water due to climate change has added 0.8 milliseconds to the day between 1990 and now.
However, under a high-emissions scenario, where greenhouse gas emissions are not reduced, the researchers predict that the rate of change could double by 2100.
While humans may not feel the effects, space missions like NASA’s Ingenuity probe (pictured) could miss their targets if the planet’s rotation changes
By the end of the century, climate change could add 2.62 milliseconds per century, making it the single largest factor altering the length of the day.
These effects will be so subtle that people will not notice the change in a lifetime. However, the researchers warn that this could have major implications for space travel.
Dr. Soja says: ‘Even if the Earth’s rotation changes only slowly, this effect must be taken into account when navigating in space, for example when directing a space probe to land on another planet.’
Over the vast distances that planetary probes like NASA’s Perseverance and Ingenuity travel, a deviation of just one centimeter on Earth can mean missing the target by hundreds of meters.
This is especially important for precision landings that aim to land in very specific places on distant planets.
Scientists need to accurately estimate the exact direction of the Earth’s rotation for future space missions.
As the Earth’s liquid metal outer core shifts, it causes the Earth to wobble slightly on its axis, an effect known as polar motion
The researchers used precise measurements to separate the effects of core dynamics from the effects of surface changes on the planet’s polar motion
The researchers believe that climate change could be affecting conditions in Earth’s inner core, causing the shift in the rotational axis illustrated by the blue line in this graph.
Dr. Soja adds: ‘Otherwise it would not be possible to land in a specific crater on Mars.’
The researchers found that climate change is not only altering the Earth’s rotational speed, but also potentially causing the planet to tilt on its axis.
The scientists used a technique called Very Long Baseline Interferometry, which measures how long it takes for radio signals from space to reach Earth.
This allowed them to make very precise measurements of the Earth’s ‘polar motion’, the change in the axis of rotation relative to the Earth’s surface.
They found that changes in polar motion are jointly influenced by a combination of changes at the Earth’s surface and shifts deep within the Earth’s liquid metal outer core.
As the mass within the Earth shifts under the enormous pressure of the outer layers, the planet tilts slightly on its axis.
Shifts in the water surface have a similar effect, but the researchers also made the surprising discovery that climate change can also affect conditions deep inside the Earth.
Dr. Soja says, “Climate change is causing the Earth’s rotational axis to move, and it appears that the feedback from conservation of angular momentum is also changing the dynamics of the Earth’s core.”
The researchers found that this feedback effect can lead to changes in the Earth’s tilt over time.
However, it is unlikely that these will have any serious or noticeable effects on the surface.
Co-lead author Dr Diani Shahvandi from ETH Zurich adds: ‘Ongoing climate change could even affect processes deep inside the Earth and have a wider reach than previously assumed.’