Melting ice and climate change threaten to have a greater impact on the length of days on Earth than the pull of the Moon’s gravity by the end of the century.
The Earth’s rotation is gradually slowing down, making our days a little longer. Scientists say the current pace of this change could be unlike anything seen by at least 3.6 million years.
Although a day is often defined as having 24 hours, the Earth’s rotation is not perfectly constant. Small variations occur naturally due to the gravitational attraction of the Moon and complex processes inside the planet, on its surface and in the atmosphere. These fluctuations can cause days to be marginally shorter or longer by fractions of a millisecond.
For example, in July and August 2025, the position of the Moon caused the Earth’s rotation to slow slightly, lengthening the days in just over a millisecond compared to the average. But scientists say a more significant long-term trend is emerging, driven primarily by climate change.
As global temperatures rise, ice caps and mountain glaciers are melting at an accelerated rate. Meltwater flows into the oceans, contributing to rising sea levels and redistributing mass across the planet. This Change in mass affects Earth’s rotation.
Researchers compare the phenomenon to a figure skater on a wheelA: When skaters extend their arms outward, their rotation decreases. Likewise, when large volumes of ice melt and spread across the oceans, more of the Earth’s mass moves from the planet’s axis of rotation, near the poles, toward the equator. This redistribution acts as a brake on the planet’s rotation.
A new one by scientists at the University of Vienna and ETH Zurich examined geological and climate data to determine whether similar slowdowns have occurred in the past. By reconstructing the history of Earth’s rotation until the end of the Pliocene, which corresponds to approximately 3.6 million years ago, the team found that the current increase in day length seems to be unprecedented.
According to research, the day on Earth is currently become longer by about 1.33 milliseconds per century. The main factor is the rise in sea level caused by melting ice, which changes the distribution of the planet’s mass and slows its rotation.
Scientists warn the effect is likely to intensify. With global warming and the melting of polar ice caps, the impact of climate change on the Earth’s rotation can become even strongerpotentially surpassing the influence of the Moon by the end of the century.
While the change is imperceptible to everyday humans, it can pose challenges for technologies that rely on extremely precise time measurements. Systems like GPS satellitesspace navigation and high-speed financial networks rely on precise measurements of the Earth’s rotation, and even millisecond variations can require adjustments.
