ZURICH — Human-driven climate change is now significantly altering the Earth’s physical rotation, lengthening the calendar day at a pace unprecedented in nearly 4 million years, according to a landmark study released by researchers at ETH Zurich.
The findings, published in the journal Proceedings of the National Academy of Sciences (PNAS), reveal that the melting of polar ice sheets is redistributing mass toward the equator. This shift acts as a planetary brake, slowing the Earth’s spin through a physical phenomenon known as the “figure skater effect.” Just as a skater slows their spin by extending their arms, the Earth slows as water mass moves from the poles toward the center of the globe.
A Geological Anomaly
While the Earth’s rotation has historically been governed by the gravitational pull of the moon, researchers found that climate-related factors are currently increasing day length by approximately 1.33 milliseconds per century.
“This rapid increase implies that the rate of modern climate change has been unprecedented at least since the late Pliocene, 3.6 million years ago,” stated Professor Benedikt Soja, a geodesist at ETH Zurich.
By utilizing deep learning algorithms and analyzing the chemical composition of benthic foraminifera—single-celled marine fossils—the team reconstructed sea-level fluctuations dating back millions of years. Their data indicates that while the planet’s spin has varied during past glacial cycles, the current acceleration is an outlier.
Surpassing the Moon
The study warns that if greenhouse gas emissions continue at their current trajectory, the influence of climate change on the Earth’s rotation will surpass the slowing effect of the moon by the end of the 21st century.
“Never before has the planetary ‘figure skater’ raised her arms and sea levels so quickly as observed between 2000 and 2020,” said co-author Mostafa Kiani Shahvandi of the University of Vienna.
Impact on Global Infrastructure
Though a few milliseconds may seem negligible to the average person, the implications for modern technology are profound. Precise Earth rotation data is critical for:
- Space Navigation: Calculating trajectories for interplanetary missions.
- GPS Systems: Maintaining the accuracy of satellite-based positioning.
- Financial Markets: Synchronizing high-frequency trading timestamps.
The research underscores that human activity is no longer just affecting the atmosphere and oceans, but is fundamentally altering the mechanical behavior of the planet itself.
