Earth’s rotation has always fluctuated, shaped by natural forces such as lunar gravity and shifting mass within the planet. What’s changed is the driver. Human-induced climate change is now accelerating these variations, with melting ice sheets quietly altering the length of a day, tells the Refractor article.
The mechanism is rooted in basic physics. As global temperatures rise, large ice sheets and glaciers melt, adding water to the oceans and raising sea levels. This redistributes mass toward the equator, making Earth slightly more oblate. Much like a spinning figure skater extending their arms, this redistribution slows the planet’s rotation. As a result, the length of a day increases.
Historically, such changes unfolded over millions of years. Geological records show that ice sheet growth and retreat caused day-length variations of 10–30 milliseconds, but at extremely slow rates. Today, that pace has shifted dramatically. Modern climate change has pushed the rate of increase in day length to about 1.33 milliseconds per century, the fastest seen in roughly 3.6 million years.
To understand this shift, researchers used paleoclimate data from fossils and coral reefs, feeding it into deep learning models capable of reconstructing Earth’s rotational history. These models reveal that while past changes were larger in magnitude, they occurred gradually. The current trend is smaller in scale but far more rapid, signaling a unique moment in Earth’s history.
The implications extend beyond abstract measurements. Even slight mismatches between Earth’s rotational time and atomic time can disrupt global systems. Technologies such as satellite navigation, space missions, and computer networks rely on precise timing. As rotational changes accelerate, the need to adjust clocks through leap seconds may become more frequent, introducing technical challenges.
What appears as a barely noticeable shift in day length reflects a deeper planetary transformation. The melting of ice sheets is not just raising sea levels; it is subtly reshaping the rhythm of Earth itself, linking climate change to the very way time is measured.