Something invisible and immense is happening beneath your feet. Published research from the University of Vienna and ETH Zurich now establishes that human activity has pushed the planet's rotation into territory unlike anything in 3.6 million years — and the engineers who keep GPS working are already watching the numbers.
The finding, published in March 2026 in the Journal of Geophysical Research: Solid Earth by researchers Mostafa Kiani Shahvandi and Benedikt Soja, quantifies precisely what glaciologists and geodesists had been building toward: Earth's days are currently lengthening at 1.33 milliseconds per century due to climate-driven ice melt and sea-level rise. That rate is, by the geological record stretching back to the Late Pliocene, without precedent.
A companion finding — from a separate 2023 study by Ki-Weon Seo and colleagues at Seoul National University — adds a second human fingerprint: agricultural groundwater extraction shifted Earth's rotational pole roughly 80 centimeters eastward between 1993 and 2010 alone, making groundwater pumping the single largest climate-related driver of polar drift, according to that research.
Together, the two lines of work establish something that the prior generation of Earth scientists could not have stated with confidence: humanity has become, in the span of decades, a geological force potent enough to alter the mechanics of how the planet moves through space.
Days Are Getting Longer: How Researchers Measured 3.6 Million Years of Earth's Spin
The 2026 ETH Zurich/University of Vienna study posed a deceptively simple question: has anything like today's rate of rotational change happened before? Answering it required looking back millions of years — well beyond any instrumental record.
The team built their paleoclimate archive from the fossilized shells of benthic foraminifera, single-celled marine organisms that live on the ocean floor. These shells record the oxygen isotopic composition (δ¹⁸O, or delta-18 oxygen) of the seawater in which the organisms lived. When global ice volume increases, the ocean's ratio of heavier oxygen-18 to lighter oxygen-16 rises — lighter water is preferentially locked into polar ice sheets. That chemical signal, preserved in millimeter-scale calcium carbonate shells at the bottom of ancient ocean sediment cores, becomes a direct proxy for sea-level history.
From sea-level fluctuations, the team could mathematically derive changes in day length using Liouville's equations — the governing equations of Earth rotation — because redistributing water mass between high-latitude ice and equatorial oceans changes the planet's moment of inertia, much like a figure skater extending their arms to slow a spin.
To handle the large statistical uncertainties inherent in data stretching back nearly four million years, Shahvandi and Soja developed a new deep learning methodology called a Physics-Informed Diffusion Model (PIDM). The PIDM integrates physical laws governing sea-level change directly into a probabilistic neural network — it does not merely fit a curve to noisy data, but instead constrains its outputs to be physically plausible at every step. "This model captures the physics of sea-level change, while remaining robust to the large uncertainties inherent in paleoclimate data," Kiani Shahvandi explained in the study press release.
The verdict was unambiguous. Today's 1.33-millisecond-per-century rate stands alone in the entire record. One prior episode, roughly two million years ago, approached today's values — but it resulted from what Soja describes as a coincidence of fragile ice sheets and a temporary natural CO₂ spike. That event was an anomaly; today's trend is driven by sustained, human-caused warming.
"This rapid increase in day length implies that the rate of modern climate change has been unprecedented at least since the late Pliocene, 3.6 million years ago," said Soja, Professor of Space Geodesy at ETH Zurich. "The current rapid rise in day length can thus be attributed primarily to human influences."
Groundwater Extraction Effects: How Agricultural Pumping Moved Earth's Pole
The rotational-pole story involves a different but equally striking mechanism. Earth's rotational pole — the geographic point through which the planet's axis passes — does not stay fixed. It wanders continuously in response to mass redistributions across the surface. What the 2023 Seoul National University study showed is that groundwater extraction alone shifted the pole roughly 80 centimeters eastward between 1993 and 2010.
The team used data from NASA's GRACE (Gravity Recovery and Climate Experiment) mission, a twin-satellite system that detects variations in Earth's gravitational field by measuring the precisely tracked separation between the two spacecraft via a K-band microwave ranging system. As groundwater moves from underground aquifers into rivers and eventually into the ocean, the resulting mass redistribution alters the planet's gravitational field at a level detectable from orbit. Those changes map to specific alterations in the degree-2 order-1 Stokes coefficients of Earth's geopotential — the mathematical parameters that describe how polar motion is excited.
The study modeled the observed polar drift against scenarios with and without groundwater redistribution. Only the scenario that included 2,150 gigatons of groundwater depletion — pumped primarily from aquifers in western North America and northwestern India — matched what GRACE actually measured.
"Our study shows that among climate-related causes, the redistribution of groundwater actually has the largest impact on the drift of the rotational pole," said Ki-Weon Seo, geophysicist at Seoul National University and lead author of the 2023 study.
The energy involved in producing even the day-length component of this shift is substantial. As lead author Kiani Shahvandi described the rotational energy change: it is equivalent in scale to a magnitude-9.0 earthquake — not in terms of ground shaking, but in sheer planetary-scale force rearrangement.
GPS Navigation Accuracy and Spacecraft Systems: What Changing Rotation Demands
For most people, a millisecond-scale shift in day length is imperceptible. For the infrastructure of global navigation and spacecraft operation, it represents a continuously updated calculation problem.
GPS and global navigation satellite systems depend on precise knowledge of Earth's rotation rate — specifically the parameter called UT1 (Universal Time 1), which tracks how much the Earth has actually rotated relative to an inertial reference frame. Any drift between UT1 and atomic clock time must be corrected. The International Earth Rotation and Reference Systems Service (IERS), hosted partly at the U.S. Naval Observatory and the Observatoire de Paris, publishes daily Earth Orientation Parameters — a package of corrections that GPS receivers, VLBI telescopes, and spacecraft navigation systems ingest continuously to maintain positional accuracy.
It is worth being precise about the current situation. GPS systems already handle rotational corrections far larger than 1.33 milliseconds per century — they absorb a full hour of change twice a year for daylight saving time adjustments, and have added 27 leap seconds to UTC since 1972. The IERS infrastructure is already built to handle known variability.
What the 2026 research changes is the engineering challenge going forward. The prior dominant driver of day-length change was the Moon's gravitational tidal friction — a steady, predictable deceleration of approximately 2.4 milliseconds per century. Predictable forces are easier to model and correct for. Climate-driven ice melt, by contrast, varies year to year with weather patterns, El Niño cycles, and regional ice dynamics. As Soja notes, even a 1-centimeter position error rooted in uncorrected rotational drift can propagate to a deviation of hundreds of meters when navigating a spacecraft toward another planet.
Michael Mann, Presidential Distinguished Professor of Earth and Environmental Science at the University of Pennsylvania, noted that instruments requiring precise knowledge of Earth's rotation rate — including those used aboard spacecraft — may need recalibration as the rate of change increases.
The timekeeping community is already adapting. Duncan Agnew, Professor of Geophysics at the University of California San Diego, showed in a 2024 study published in Nature that climate-driven rotational slowdown has delayed the likely need for a negative leap second from around 2026 to 2029. In 2022, an international panel of metrologists voted to eliminate leap seconds entirely by 2035 in favor of larger, less-frequent timekeeping adjustments. The working group is expected to finalize those details at a meeting later in 2026.
Length of Day Increase at End of Century: What High-Emissions Projections Show
The 2026 study also projects a future trajectory that depends heavily on which emissions path civilization follows.
In the higher-emissions scenario — sustained fossil fuel use, global temperatures rising 3°C to 5°C — the day-length-change rate accelerates to approximately 2.62 milliseconds per century by 2080, exceeding the Moon's tidal influence for the first time in Earth's history. In a low-emissions, high-mitigation scenario, the rate remains closer to today's level. The difference is consequential: crossing the threshold where climate exceeds lunar influence would mark the first time in Earth's history that a species has become the dominant force shaping the planet's rotation. It would also increase the inherent unpredictability of the IERS's correction models, since ice melt is far less regular than lunar tidal friction.
"The most important takeaway is that human influence on the Earth system has become so profound that we are now changing the very way our Earth spins," Soja said.
The researchers are now examining other human-driven mass redistribution events — particularly groundwater depletion and water-cycle changes driven by climate change — to build a fuller picture of how Earth's spin is being shaped by the choices civilization makes.
How Do Scientists Detect Changes in Earth's Rotation?
Detecting changes in Earth's rotation requires two fundamentally different measurement approaches for the two effects described in these studies.
For day-length changes, modern scientists use Very Long Baseline Interferometry (VLBI) — a technique that times the arrival of radio signals from distant quasars at arrays of radio telescopes separated by thousands of kilometers. Because quasars are effectively fixed points in the cosmos, the precise arrival-time differences encode how fast Earth is rotating. VLBI can measure UT1 to better than a microsecond. For polar motion, GRACE satellite gravimetry directly maps the mass redistribution that drives the pole's wandering — converting gravitational field variations into polar motion excitation forces via the degree-2 Stokes coefficients. For the deep-time reconstruction in the 2026 study, the δ¹⁸O chemistry of benthic foraminifera shells served as the proxy archive, with the PIDM algorithm bridging the gap between geological uncertainty and quantitative day-length estimates.
Frequently Asked Questions
How does climate change affect Earth's rotation?
Melting polar ice redistributes mass from high-latitude ice sheets to the equatorial ocean, increasing Earth's moment of inertia and slowing its spin — much like a figure skater extending their arms mid-spin. A 2026 study in the Journal of Geophysical Research: Solid Earth found this process is currently lengthening days at 1.33 milliseconds per century, a rate without precedent in the 3.6-million-year geological record examined.
Why are days getting longer due to climate change?
As Greenland and Antarctic ice sheets melt, the meltwater flows into the ocean and spreads toward the equator. This movement of mass away from the poles reduces Earth's rotational speed through conservation of angular momentum. The same physics operates when groundwater pumped from mid-latitude aquifers eventually reaches the ocean, contributing both to sea-level rise and to the redistribution of planetary mass.
Does melting ice slow Earth's spin?
Yes. Sea-level rise driven by ice melt is the primary mechanism behind the current slowdown in Earth's rotation. Researchers quantified this link by reconstructing ancient sea levels from benthic foraminifera fossil chemistry and applying Liouville's equations to derive the corresponding day-length history. No comparable rate of climate-driven day-length increase appears in the 3.6 million years of geological record examined.
How does Earth's rotation affect GPS accuracy?
GPS systems rely on precise knowledge of Earth's rotation parameters, which are published daily by the International Earth Rotation and Reference Systems Service and continuously ingested by navigation systems. An accelerating, increasingly unpredictable rate of rotational change — driven by variable ice melt rather than the steady lunar tidal deceleration — raises the precision demands on these corrections. Spacecraft navigation is particularly sensitive: researchers note that even a 1-centimeter position error on Earth can grow to hundreds of meters at interplanetary distances.
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