The length of Earth’s days is increasing – though by minuscule amounts – and the primary driver is climate change. A new study reveals that our planet’s rotation is slowing at a rate that hasn’t been seen in at least 3.6 million years, with each day now extending by approximately 1.33 milliseconds per century. While seemingly insignificant, this shift has implications for precision technologies like space navigation and underscores the far-reaching effects of global warming.
How Climate Change Alters Earth’s Spin
The mechanism behind this change is tied to rising sea levels. As glaciers and polar ice sheets melt, water redistributes from the poles toward the equator. This shift in mass alters Earth’s moment of inertia, similar to how a figure skater slows down when extending their arms. The more mass moves away from the rotational axis, the slower the planet spins.
This isn’t a new phenomenon; day length has fluctuated naturally over millions of years in response to ice ages and interglacial periods. However, the current rate of increase is exceptional. Researchers analyzed fossil records to reconstruct sea-level changes over geological time, then used deep-learning algorithms to model the physics behind these shifts. The results confirm that the speed at which days are lengthening today is an anomaly.
The Growing Influence of Climate Over Lunar Forces
Traditionally, the moon’s gravitational pull has been the dominant factor influencing Earth’s rotation. But according to geophysicist Benedikt Soja, the study’s senior author, climate change is poised to surpass the moon’s influence by the end of this century. This means that human-caused warming is now a major force shaping fundamental planetary dynamics.
The implications extend beyond abstract science. The slowing rotation requires adjustments in precise timing systems, particularly in space navigation where even millisecond-level errors can accumulate over time.
“Even though the changes are only milliseconds, they can cause problems in many areas, for example in precise space navigation, which requires accurate information on Earth’s rotation,” Soja explained.
This is a clear reminder that climate change isn’t just about rising temperatures or extreme weather; it’s fundamentally reshaping the planet’s physical properties. The lengthening days are a subtle but measurable consequence of our changing world.
The study underscores how interconnected Earth’s systems are, and how even seemingly small changes can ripple through multiple domains. The acceleration of this effect is a direct result of unprecedented human-caused warming, and highlights the urgency of addressing climate change before it alters the planet in irreversible ways.
