For generations, a day on Earth has been treated as one of the few constants in human life: 24 hours, no more, no less. But scientists now say that assumption is slowly changing — and climate change is partly responsible. 

According to recent research by scientists from the University of Vienna and ETH Zurich, Earth’s rotation is gradually slowing as global warming melts glaciers and polar ice sheets. The effect is tiny, measured in milliseconds, but researchers say the trend is now occurring at a rate not seen in the past 3.6 million years. 

The reason lies in a basic law of physics. 

As rising temperatures melt vast amounts of ice in Greenland, Antarctica and mountain glaciers, water that was once concentrated near Earth's poles flows into the oceans and spreads toward the equator. This redistribution of mass changes how the planet spins. 

Scientists often compare it to a figure skater. When a skater stretches out their arms, their rotation slows. Earth behaves in a similar way: moving mass away from its axis causes the planet's spin to become slightly slower, lengthening the day. 

Days are getting longer 

The increase is far too small for humans to notice. 

Researchers estimate that the length of a day is currently increasing by about 1.33 milliseconds per century because of climate-related changes. While that may sound insignificant, scientists stress that the amount of mass involved is enormous. 

Professor Benedikt Soja, one of the study's authors, noted that such a change requires roughly 1,000 gigatonnes of ice and water to move from the polar regions into the oceans. 

To put that in perspective, researchers compared the energy involved in the shift to the scale of a magnitude-9 earthquake — not in terms of destruction, but in terms of the planetary forces required to alter Earth's rotation. 

Ancient planetary signal hidden in fossils 

To understand whether such rapid changes had happened before, scientists looked deep into Earth's geological history. 

The team analysed fossilised remains of microscopic marine organisms known as benthic foraminifera. The chemical composition preserved in their shells contains clues about ancient sea levels and ice-sheet behaviour. By combining these records with modern climate data and machine-learning models, researchers reconstructed changes in Earth's rotation going back around 3.6 million years. 

Their conclusion: today's climate-driven slowdown stands out in the geological record. 

Researchers identified only one comparable period roughly two million years ago, when significant ice-sheet melting also altered Earth's rotation. However, they say the current trend is unusual because it is being driven largely by human-caused warming. 

More than a curious scientific fact 

A few milliseconds may seem irrelevant to every day life, but precise timing is critical for modern technology. 

Satellite navigation systems, GPS networks, telecommunications infrastructure and space missions all rely on extremely accurate measurements of time and Earth's rotation. Even tiny changes can create challenges for systems that depend on nanosecond-level precision. 

Scientists say climate change could eventually become a stronger influence on day length than some natural factors that have historically shaped Earth's rotation, including certain lunar effects.

Published on: May 31, 2026 3:46 PM IST