That rate is so slow that it will take two hundred million years to add a single hour to the day. There is no calendar date to circle. The 25-hour day is a geological certainty, not a scheduling conflict.<\/p>\n
![\"Moon,and,earth.,the,moon,is,natural,satellite,orbiting,earth.\"](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/04\/Lunar-tides-have-slowed-Earth-for-billions-of-years.jpg.webp.webp\")
Lunar tides have slowed Earth for billions of years, but climate-driven ice melt is now disrupting that ancient rhythm. Image credit: Shutterstock<\/p>\n
But that ancient, predictable rhythm is being disrupted. Researchers led by Mostafa Kiani Shahvandi of ETH Zurich analyzed more than 120 years of data and found that climate-driven mass shifts are now accelerating the slowdown beyond what the Moon alone can explain.<\/p>\n
Melting Ice Is Flattening the Planet<\/p>\n
Between 2000 and 2018, the lengthening of day attributed specifically to melting ice and groundwater depletion reached 1.33 milliseconds per century. In the prior hundred years, that same contribution never exceeded 1.0 millisecond per century. The full findings are detailed in a NASA Earth science report<\/a> published in July 2024.<\/p>\n The physics is intuitive. When the massive ice sheets of Greenland <\/a>and Antarctica melt, the water does not stay at the poles. It flows into the equatorial ocean. This redistributes mass toward Earth\u2019s midsection, flattening the planet\u2019s shape by a tiny but measurable amount. A flatter sphere spins more slowly. The principle is identical to an ice skater extending their arms to reduce their rotation speed.<\/p>\n The research team relied on satellite data from NASA\u2019s GRACE mission and its follow-on GRACE-FO to measure these mass changes with precision. They combined those observations with historical mass-balance studies to reconstruct the trend back to 1900.<\/p>\n The conclusion is stark. If greenhouse emissions continue to rise along current trajectories, the climate-driven lengthening of day could reach 2.62 milliseconds per century by the year 2100. At that point, human-driven ice melt will overtake the Moon\u2019s tidal friction as the primary brake on planetary rotation. For the first time in Earth\u2019s history, the dominant force shaping the length of a day will not be celestial. It will be terrestrial.<\/p>\n Why Milliseconds Matter to Modern Life<\/p>\n A few thousandths of a second sounds like an abstraction. To a GPS satellite, it is a catastrophic error.<\/p>\n Global positioning systems function by timing how long it takes a radio signal to travel from a satellite to a receiver on the ground. Light travels roughly 300 meters in one microsecond. If the atomic clocks that govern GPS drift out of alignment with Earth\u2019s actual orientation in space by even a tiny fraction of a second, the resulting position error can span city blocks.<\/p>\n Organizations like the International Earth Rotation and Reference Systems Service publish regular bulletins<\/a> tracking the difference between precise atomic time and the planet\u2019s irregular rotation. Since 1972, timekeepers at the National Institute of Standards and Technology<\/a> have added 27 leap seconds to Coordinated Universal Time to keep the two systems synchronized. The last leap second was inserted on December 31, 2016.<\/p>\n The accelerated melting of polar ice introduces a new and unpredictable variable into those calculations. As Adhikari\u2019s team noted, the planet\u2019s spin is no longer a purely astronomical problem. It is now a climate problem.<\/p>\n The Axis Is Wandering in Response<\/p>\n The same redistribution of mass that slows the rotation also shifts the location of the spin axis itself. Scientists refer to this phenomenon as polar motion.<\/p>\n Using machine-learning algorithms to analyze 120 years of measurements, the research team found that 90 percent of recurring fluctuations in the axis position could be explained by changes in groundwater, ice sheets, glaciers, and sea level. The axis has wandered by approximately 30 feet<\/a> over the past century. <\/p>\n A sudden eastward drift that began around 2000 was traced directly to accelerated melting in Greenland and Antarctica and to groundwater depletion in Eurasia. The evidence converges on a single point. Climate-driven changes in surface mass are now detectable at the scale of the entire planet.<\/p>\n The Long Goodbye to 24 Hours<\/p>\n A study from the University of Toronto<\/a> published in Science Advances <\/a>offers a useful reminder of how unusual this moment is. Led by theoretical astrophysicist Norman Murray, the research showed that for more than a billion years, the length of Earth\u2019s day held steady at 19.5 hours. An atmospheric tide driven by the Sun resonated with the planet\u2019s rotation, perfectly counteracting the Moon\u2019s braking effect. That natural stalemate ended long before humans arrived.<\/p>\n The current acceleration is not natural. It is a direct consequence of ice loss driven by rising global temperatures. The length of day will reach 25 hours eventually, but it will arrive on a planet shaped by forces we are only beginning to measure.<\/p>\n![\"Beautiful,carved,ice,shelf,wall,in,antarctica.,view,from,ship\"](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/04\/Water-flowing-from-melting-poles-to-the-equator-flattens-Earth-slightly.jpg.webp.webp\")
Water flowing from melting poles to the equator flattens Earth slightly, slowing its rotation like a skater extending their arms. Image credit: Shutterstock<\/p>\n![\"Satellite,orbiting,earth,at,night,with,glowing,city,lights,below.\"](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/04\/A-tiny-rotational-drift-causes-GPS-errors-of-hundreds-of-meters.jpg.webp.webp\")
A tiny rotational drift causes GPS errors of hundreds of meters, forcing timekeepers to add leap seconds to atomic clocks. Image credit: Shutterstock<\/p>\n![\"Image\"](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/04\/image-79.png\")
The north magnetic pole, the point on the Earth where a compass needle would point down, is sliding about 35 miles closer to Russia each year. Credit: Jonathan Corum | National Oceanic and Atmospheric Administration<\/p>\n