Climate Change May Be Making Our Days A Little Longer — Here’s How We Know

Climate change appears to be making our days a little longer. According to a study published in the Journal of Geophysical Research: Solid Earth, rising sea levels are slowing the Earth’s spin.

At a rate of 1.33 milliseconds per century, it is not enough to squeeze in a quick workout or watch another episode of Bridgerton, but the new paper shows just how unusual it is. Lead author Mostafa Kiani Shahvandi told Discover the rate we see today is “almost unprecedented” — a fact that “shows this anomalous rate is anthropogenic.”

Read More: The Moon Is Moving Farther From Earth Each Year, and Tides Are the Reason

The Impact Of Rising Sea Levels On Earth’s Spin

While the 24-hour day has become a fixture of the calendar, the Earth’s rotation is open to variation. Factors such as the moon’s gravitational pull and geophysical processes can influence the planet’s rotational speed, and even without human intervention, it can vary by approximately 30 milliseconds. Crucially, however, these fluctuations occur on time scales lasting hundreds of thousands of years.

A 2024 study in PNAS highlighted another factor that can affect the speed of Earth’s rotation — rising sea levels caused by glacial melt, itself a result of climate change. According to the researchers’ calculations, from 2000 to 2020, the length of the day has increased at a rate of 1.33 milliseconds per 100 years.

“The fact that since the outset of [the] 21st century, the length of day is increasing so rapidly is astounding,” said Kiani Shahvandi of the Meteorology and Geophysics Department at the University of Vienna.

This change is due to the redistribution of mass that occurs when glaciers melt, and sea levels rise. In a press release, Kiani Shahvandi compared the Earth to a figure skater “who spins more slowly once they stretch their arms, and more rapidly when they keep their hands close to the body.”

An “Unprecedented” Trend

In this new paper, Kiani Shahvandi and co-author Benedikt Soja, Professor of Space Geodesy at ETH Zurich, set out to determine whether there were any other periods in history when day length increased at a similar pace.

To do so, the researchers used benthic foraminifera fossils, a single-celled marine organism. Analyzing the chemical composition of these fossils enabled the pair to detect sea-level changes. Using a probabilistic deep learning algorithm, they were then able to reconstruct 3.6 million years of day-length variations.

They note just one period, approximately 2 million years ago, when the rate of change in the length of day was nearly comparable — a shift caused by the waxing and waning of ice sheets.

“This rapid increase in day length implies that the rate of modern climate change has been unprecedented at least since the late Pliocene,” Soja said in a press release.

If current trends continue, the researchers predict climate change will have a greater effect on day length than the moon by the end of this century. Under a high-emission scenario, where emissions continue to rise unmitigated, estimates suggest the length of the day could increase at a rate of up to 2.62 milliseconds per century as we approach the year 2100, according to the 2024 PNAS study.

What Increased Day Lengths Could Mean

When the 24-hour day contains 86,400 seconds, a few milliseconds may not seem like a lot. But there are certain instances where even slight variations in time could cause problems

“Precise timekeeping will be in trouble, because there would be leap seconds, which cause problems in computer networks,” Kiani Shavandi told Discover. (Not too dissimilar to a leap day in a leap year, leap seconds are used to ensure atomic clocks align with the Earth’s rotation.)

This, in turn, could impact space and satellite navigation, which rely on highly accurate data about Earth’s rotation.

Moving forward, the team hopes to continue digging into the paleoclimate archives to better understand past changes in Earth’s rotation.

Read More: Earth’s Rotation Has Slowed Down Over Billions of Years

Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article: