Climate Change Causes Earth's Rotation to Slow, Days to Lengthen – Study

Jakarta, CNBC Indonesia - Unbeknownst to humans, the duration of a day is slowly but steadily increasing. The Earth’s rotation has slowed in recent decades to a degree not seen in 3.6 million years. This phenomenon is a stark indicator of how human activity has transformed the planet, even affecting its movement in space. Recent research by a joint team from the University of Vienna and ETH Zurich reveals that this slowdown is no longer solely due to the Moon’s gravitational pull, as previously thought, but is now significantly driven by climate change and global warming. Each day, the time required for Earth to complete one full rotation increases by a few milliseconds. While the figure seems small, the force required to alter Earth’s rotation is immense. The primary cause of the slowing rotation is the melting of polar ice caps and glaciers due to rising global temperatures. Water previously locked in ice at high latitudes is now melting and flowing into the oceans, spreading slowly towards the equator. This massive redistribution of water alters the planet’s weight distribution. The principle is similar to an ice skater spinning: when they extend their arms, their rotation slows compared to when arms are pulled in. Similarly, as water mass moves away from the rotational axis toward the equator, Earth’s spin slows dramatically. While Earth’s rotation has always slowed naturally due to the Moon’s gravitational pull, this new research shows climate change is now a force of equal magnitude, and is predicted to dominate over the Moon’s influence by the end of this century. Professor Benedikt Soja from ETH Zurich, one of the study’s authors, explained: ‘The current climate-driven change in day length is occurring at a rate of 1.33 milliseconds per century. This may sound trivial, but the mass shift is extraordinary.’ To grasp the scale, this shift is equivalent to moving about 1,000 gigatonnes of water from the poles to the oceans. ‘Imagine a solid ice block 10 kilometres high—taller than Mount Everest—covering all of New York City. That is the mass in motion,’ he added. From an energy perspective, Mostafa Kiani Shahvandi, lead researcher from the University of Vienna, stated: ‘This change in Earth’s rotational energy is equivalent to the energy released by a magnitude 9.0 earthquake.’ This refers not to physical damage on land, but the sheer force moving planetary scales. To determine if this phenomenon has occurred before, researchers examined geological records dating back 3.6 million years to the Late Pliocene. They used fossilised single-celled marine organisms called benthic foraminifera. The chemical composition of their shells recorded ancient sea level changes, allowing scientists to reconstruct past variations in Earth’s rotation speed. Using artificial intelligence to analyse this ancient data, they found no geological evidence of such rapid and massive water mass shifts. A rare event approximately two million years ago came close to current conditions, triggered by natural carbon dioxide spikes and fragile ice sheets. However, such an event has not recurred naturally since. ‘That rare event is now recurring, but not due to nature—human activity. We are capable of generating planetary-scale forces in less than a century,’ Soja stressed. If the world continues to rely on fossil fuels and global temperatures rise by 3 to 5 degrees Celsius, researchers predict climate change’s impact on Earth’s rotation will surpass the Moon’s gravitational effect before 2100. Even tiny time discrepancies are critical for the accuracy of Earth-based GPS positioning and navigation systems, as well as spacecraft guidance across the solar system. This rotational shift is a stark reflection of humanity’s profound impact on Earth’s systems. The mass movement of water coincides with rising sea levels and more frequent extreme weather, both of which will significantly affect human habitability in the future. ‘The key takeaway is that human influence on Earth’s systems has become so profound. We have altered the planet’s rotation—the most fundamental mechanism of its existence,’ Soja concluded. Researchers are now investigating other human activities, such as groundwater depletion and altered water cycles, to assess their impact on Earth’s once thought immutable rotation.