Climate Change Slows Earth’s Rotation

Recent scientific research suggests that the length of a day on Earth is gradually increasing as the planet’s rotation slows. Although the change is extremely small, scientists warn that it is occurring at an unprecedented rate due largely to human-driven climate change. The findings highlight how global warming is not only altering weather patterns and sea levels but also affecting fundamental physical processes of the planet.

The study, published on 13 March by researchers from the University of Vienna and the Swiss Federal Institute of Technology in Zurich, indicates that the length of an Earth day is currently increasing by about 1.33 milliseconds per century. While this may appear insignificant, the researchers say the rate of change is the fastest observed in approximately 3.6 million years.

The primary cause lies in the rapid melting of polar ice sheets and glaciers. As global temperatures rise, large quantities of ice from regions such as Greenland and Antarctica are melting and flowing into the oceans. The resulting redistribution of water gradually shifts mass from the polar regions towards the equator. This change in mass distribution affects the planet’s rotational dynamics.

Scientists often explain this process through an analogy with a figure skater. When a skater spins with arms close to the body, the rotation is fast. When the arms are extended outward, the rotation slows because the mass is distributed farther from the axis of rotation. Earth behaves in a similar way: as mass moves away from the rotational axis, the planet’s spin becomes slightly slower, lengthening the day.

Professor Benedikt Soja of the University of Vienna noted that the recent rate of change is highly unusual compared with natural climate cycles of the past. According to him, although Earth’s rotation has fluctuated many times throughout geological history, the acceleration of change observed between 2000 and 2020 stands out as exceptional.

He explained that even a tiny fraction of a millisecond matters in modern technological systems. Many advanced technologies depend on extremely precise time measurement. A small variation in Earth’s rotational speed can therefore influence systems that rely on exact timing.

For example, spacecraft navigation requires highly accurate calculations of time and position. Satellite-based navigation systems also depend on precise synchronisation between satellites and ground receivers. Even the global network of atomic clocks used to maintain international time standards could be affected by gradual shifts in Earth’s rotation.

To understand how the length of days changed in the distant past, scientists examined fossils of benthic foraminifera, microscopic single-celled marine organisms that lived millions of years ago. The chemical composition of their shells preserves clues about historical sea levels. By analysing these fossils and combining the data with a physics-based machine learning model, researchers reconstructed changes in Earth’s rotational speed over millions of years.

Their findings suggest that around two million years ago, when Greenland was largely free of ice and covered by forests, Earth’s rotation slowed slightly due to natural environmental changes. However, the speed of the present change appears far greater than any comparable natural variation recorded in that long geological record.

The study also suggests that climate change could become an even more significant factor in Earth’s rotation later in this century. By the 2080s, the effect of melting ice and shifting ocean mass may exceed the influence of the Moon’s gravitational pull, which has historically been the main driver of long-term changes in Earth’s rotation.

Key findings from the research are summarised below:

Although the extension of a day by a few milliseconds may seem trivial in daily life, the research demonstrates how deeply human activity can influence planetary systems. Scientists say the findings serve as another reminder that climate change has consequences extending far beyond rising temperatures, affecting even the rotation of the planet itself.