Human Climate Change Slows Earths Rotation

A new study reveals that human-driven climate change is slowing Earth's rotation, subtly lengthening the average day in a way unseen for millions of years. Researchers from the University of Vienna and the Swiss Federal Institute of Technology Zurich analyzed geological records and found that melting polar ice sheets and glaciers are redistributing water toward the equator, adding about 1.33 milliseconds to the length of a day every century. This effect, driven primarily by global warming since the late 20th century, marks the fastest rate of change in at least 3.6 million years.

The slowdown stems from the conservation of angular momentum, a principle that governs rotating bodies. As ice at the poles melts, water flows into oceans and shifts mass farther from Earth's spin axis, much like a figure skater who slows her spin by extending her arms. Lead author Mostafa Kiani Shahvandi, a geoscientist at the University of Vienna, described the process in the study: "Never before or after that has the planetary figure skater raised her arms and sea levels so quickly as in 2000 to 2020." This mass redistribution increases the planet's moment of inertia, causing the rotation to decelerate.