Recent studies indicate that the Earth is no longer rotating at a constant speed as previously believed; instead, it has begun to slow down at an unprecedented rate over the past approximately 3.6 million years. Although this slowdown is measured in fractions of a millisecond, it has tangible effects on our daily lives, particularly in global timing and modern space navigation systems.
At the International Earth Rotation and Reference Systems Service (IERS) center in Paris, scientists periodically compare the Earth's rotation with ultra-precise atomic clocks. These comparisons have revealed that the Earth has started to slow down unexpectedly over the past two decades, not due to the Moon's gravity as previously thought, but because of the movement of water on the Earth's surface resulting from climate change-induced ice melting.
Details of the Event
For billions of years, the Moon's gravity has been the primary factor slowing the Earth's rotation, as tidal friction between the Moon and the oceans transfers part of the Earth's rotational energy to the Moon, increasing the length of the day by about 1.8 milliseconds per century. This slowdown was expected and consistent, allowing scientists to accurately adjust global clocks through what are known as "leap seconds," with 27 leap seconds added since 1972.
However, in the last two decades, scientists have observed that the rate of the Earth's slowdown is no longer regular, and a new effect has emerged that was not previously known: the melting of ice and the redistribution of water around the globe. Water that was previously trapped at the poles is now flowing towards the oceans, increasing the bulge at the equator and altering the Earth's moment of inertia.
Background & Context
Scientists liken the Earth to a "figure skater"; when the skater extends their arms, their speed decreases. In the same way, the redistribution of water is causing the Earth's rotation to slow down. Researcher Mustafa Kiani Shahfandi from the University of Vienna states, "Never before has the planetary skater extended its arms so rapidly, as occurred between 2000 and 2020, due to the significant rise in sea levels."
Although the change in the length of the day seems very small—about 1.33 milliseconds per century—these time fractions accumulate over time, affecting precise systems such as the Global Positioning System (GPS) and other satellites. These systems rely on precise synchronization with the Earth's rotation, and even a slight discrepancy between atomic time and the actual rotation of the Earth can lead to positioning errors.
Impact & Consequences
Benedikt Suga, a geodesy and earth geography expert at the Swiss Federal Institute of Technology in Zurich, notes that "by the end of the century, the impact of climate change on the length of the day is expected to surpass the effect of the Moon itself, indicating that human activity has become one of the main factors influencing the Earth's rotation."
Although these changes do not significantly affect daily life, they pose a substantial challenge for sciences and technologies that depend on millisecond precision, especially in modern space, military, and technological fields.
Regional Significance
The Arab region is among the areas most affected by climate change, suffering from rising temperatures and water scarcity. The effects resulting from the slowdown of the Earth's rotation may exacerbate these issues, necessitating urgent action to address environmental challenges.
In conclusion, this discovery shows that climate change goes beyond just rising temperatures and melting ice; it even affects the rhythm of the planet itself. Understanding these phenomena is crucial to mitigating their negative impacts on technology and daily life.