Climate Change Is Slowing Earth’s Rotation, Making Days Longer

Scientists have found that Earth’s rotation is gradually slowing down, causing days to become longer—and human-driven climate change is playing a major role in this shift. Researchers from the University of Vienna and ETH Zurich report that this change is now happening at an unprecedented rate.

According to a study published on March 13, the length of a day is currently increasing by about 1.33 milliseconds per century. This is the fastest rate observed in the past 3.6 million years. The primary cause is the rapid melting of polar ice caps and glaciers due to global warming. As this meltwater moves toward the equator, it redistributes Earth’s mass, affecting its rotation.

Scientists compare this effect to a figure skater: when a skater extends their arms, their spin slows down. Similarly, as Earth’s mass shifts away from its axis, its rotation becomes slower.

Professor Benedikt Soja from the University of Vienna explained that while natural fluctuations have occurred in the past, the changes observed between 2000 and 2020 are unique in climate history. Even though a millisecond may seem insignificant, it can have serious implications for modern technology.

Precise timekeeping is essential for systems such as satellite navigation and space missions. Even tiny variations in time can affect spacecraft trajectories and the accuracy of GPS systems. Atomic clocks, which regulate global time, may also face challenges due to these changes.

To understand how day length has changed over millions of years, scientists studied fossils of a microscopic marine organism called benthic foraminifera. The chemical composition of these fossils provides clues about past sea levels. Using this data in a physics-informed machine learning model, researchers reconstructed Earth’s rotational history.

Their findings show that about 2 million years ago, when Greenland was largely ice-free and covered in forests, Earth’s rotation also slowed slightly. However, the changes caused by modern greenhouse gas emissions are happening much faster than any natural variation in the past.

Scientists warn that by the 2080s, climate change could have a greater impact on Earth’s rotation than the Moon’s gravitational pull. By the end of the century, the length of a day could increase by as much as 2.62 milliseconds per century if current trends continue.