Climate change is slowing Earth's spin: How melting ice and shifting water are subtly stretching our days

Scientists say Earth's rotation is being affected by climate change, especially through melting ice and shifting groundwater. Combined with natural forces like lunar gravity, the planet’s days are gradually becoming longer over time.

For centuries, the length of an Earth day has stayed close to 24 hours. But in reality, Earth’s spin is not constant. It slightly speeds up or slows down due to natural and, increasingly, human-driven changes. Recent scientific research shows that climate change is now playing a role in how fast our planet spins and that could eventually affect how we keep time, reports Live Science.

Moon's gravity and Earth's natural motion

The moon has always influenced Earth's rotation. As it slowly moves away from us, it reduces the Earth's spin, making our days longer over thousands of years. But on shorter timescales, the moon’s position relative to Earth’s equator can either speed up or slow down the spin.

On July 9, July 22, and August 5, 2025, the moon will be farthest from Earth's equator. This will reduce its braking effect, causing Earth to spin a bit faster, making the day slightly shorter. Think of Earth like a spinning top, where the position of outside forces can change how fast it spins.

Fastest spin on record

In 2020, scientists noticed something unusual: Earth was spinning faster than at any point since records began in the 1970s. On July 5, 2024, we even had the shortest recorded day, which was 1.66 milliseconds shorter than the standard 24 hours, the Live Science report says.

These quick changes are natural and influenced by multiple factors, including earthquakes and seasonal effects.

How climate change is stretching the day

While natural causes still dominate, scientists are now finding evidence that human activities are also affecting Earth's rotation. A NASA study covering the years 2000 to 2018 found that melting polar ice and shifting groundwater caused by global warming added 1.33 milliseconds to the length of a day each century.

This happens because melting ice and pumping groundwater move Earth’s mass away from the poles and closer to the equator — much like how an ice skater slows down by stretching their arms out. This slows Earth’s spin just slightly, but consistently.

Earthquakes and seasons can also make a difference

Sudden events like large earthquakes can also change the length of the day. The 2011 Japan earthquake made the day shorter by 1.8 microseconds. Similarly, seasonal changes affect rotation too. In the northern hemisphere’s summer, trees grow leaves and move mass away from Earth’s axis, which slows the spin slightly.

“There is more land in the northern hemisphere than the south,” said Richard Holme, a geophysicist at the University of Liverpool. “When trees grow leaves in summer, that mass shift affects the Earth’s rotation.”

Even with all these changes, most people won’t notice. The changes are too small to affect your daily life. A day would need to differ by more than 0.9 seconds before clocks or time zones would need adjustment.

However, over the years, these tiny differences add up. The International Earth Rotation and Reference Systems Service (IERS) monitors these changes. When necessary, they add a ‘leap second’ to our clocks to keep Universal Time in sync with Earth’s actual rotation.

A slow shift with big implications

Earth’s rotation is a delicate balance influenced by many forces, the moon, earthquakes, seasons, and now, climate change. While no action is needed yet, scientists continue to study these changes closely. Over long periods, they could affect everything from satellite navigation to climate models and even how we count time.