Every day, the Earth takes a little longer to complete its rotation. Although the change is only measured in fractions of a millisecond, the forces behind it are enormous. A recent study indicates that the current rate at which our days are lengthening is unprecedented in 3.6 million years of geological history.
Researchers found that the melting of polar ice sheets and glaciers due to climate change is causing water, previously stored at high latitudes, to flow into the oceans and spread towards the equator. This movement shifts mass away from the poles, slowing the planet’s rotation, much like a figure skater slows when extending their arms.
Previous studies had already noted unusual effects of climate change on Earth’s spin. The team from the University of Vienna and ETH Zurich revisited geological data and determined that today’s rate of change has not been matched in the past. To analyse millions of years, they examined fossilised remains of marine organisms, which record ancient sea levels. This helped them calculate changes in the Earth’s rotation.
Currently, the rate of climate-driven day lengthening is 1.33 milliseconds per century. While this may seem small, it signifies a massive redistribution of mass: about 1,000 gigatonnes moving from the poles to the oceans. The energy involved in this shift is comparable to a magnitude 9.0 earthquake.
Looking ahead, if high emissions continue, climate change will likely become the primary force affecting day length by the end of the century, surpassing even the Moon’s gravitational influence. The consequences, though subtle, could impact technologies like GPS navigation and reflect broader changes in the Earth’s ecosystem. The team plans to explore other factors influencing the planet’s mass distribution, such as groundwater depletion.
