Climate Change Causes Earth’s Rotation to Slow: Day Length Increases at a Pace Unseen in 3.6 Million Years

In a remarkable breakthrough that bridges paleoclimatology and Earth’s rotational dynamics, scientists have revealed that modern climate change is causing our days to lengthen at an unprecedented rate. This extension, currently measuring approximately 1.33 milliseconds per century, is primarily driven by rising sea levels induced by the accelerated melting of polar ice and mountain glaciers. The findings not only highlight the intricate connections between Earth’s changing climate and its physical rotation but also underscore the profound impact of human activities on planetary-scale processes.

The Earth’s rotation period has never been a fixed constant. Natural variations arise from gravitational interactions, especially with the Moon, and from internal geophysical processes involving Earth’s mantle, core, and atmosphere. However, recent studies have identified an additional and unexpectedly rapid influence connected to anthropogenic climate change. As ice melts and water redistributes across our planet, the mass redistribution alters Earth’s moment of inertia, causing it to spin more slowly much like a figure skater extending her arms, thereby lengthening the day.

Building upon this insight, researchers from the University of Vienna and ETH Zurich embarked on an ambitious project to investigate whether similar rapid changes in day length have occurred in Earth’s geological past. To explore this, the scientists turned to the fossilized remains of benthic foraminifera—single-celled marine organisms whose chemical signatures serve as archival records of ancient sea-level fluctuations. By analyzing these fossil records, the team could infer historic sea levels and compute corresponding changes in Earth’s rotation over millions of years.

What sets this study apart is the innovative application of a physics-informed probabilistic diffusion model, a cutting-edge deep learning algorithm designed to handle the uncertainties inherent in paleoclimate data. This model combines rigorous physical laws governing sea-level change with statistical frameworks that accommodate data imprecision, enabling a highly robust reconstruction of past fluctuations in day length. Such an approach marks a notable advancement in understanding Earth’s climate-rotation interdependencies.

Their analysis revealed that during the Quaternary period, spanning the last 2.6 million years, the cyclical growth and retreat of extensive continental ice sheets caused notable variations in Earth’s rotation speed through sea-level changes. Despite these fluctuations, the current rate of increase in day length stands out starkly when viewed against this long-term backdrop. Only once, approximately two million years ago, did the rate of change approach today’s rapid pace, suggesting that the modern climate crisis is truly exceptional in Earth’s recent history.

This acceleration in day length measured between 2000 and 2020 emerges predominantly due to climate-related factors, particularly the melting of polar ice caps and glaciers. These phenomena contribute to a redistribution of water mass from land-based ice to the oceans, altering the planet’s angular momentum balance. This mechanism slows Earth’s rotation fractionally but measurably, illustrating a novel dimension of climate change’s pervasive reach beyond surface temperature rise or sea-level height.

The analogy employed by the lead researcher, Mostafa Kiani Shahvandi, elegantly captures the physics involved: the Earth spins akin to a figure skater who modulates her spin velocity by changing the position of her arms. As the planet’s mass shifts outward—through the melting of ice sheets and subsequent sea-level rise—it effectively “stretches its arms,” causing the rotational period to increase subtly but progressively.

Professor Benedikt Soja of ETH Zurich highlights the broader implications of these findings, emphasizing that by the end of this century, the influence of climate change on Earth’s rotation could eclipse that of the Moon itself. Given the finely tuned calibration of modern technological systems like satellite navigation, telecommunications, and precise astronomical observations, even millisecond-level perturbations in day length could present significant challenges to operational accuracy.

This pioneering research also underscores humanity’s unique role in driving changes at a planetary scale, with contemporary climate trends outstripping natural variations recorded over millions of years. The integration of paleontological data, advanced modeling, and geophysical theory provides a powerful framework to forecast how ongoing environmental transformations will continue to influence Earth’s fundamental physical behaviors.

As the study demonstrates, the fossil archives preserved in minute marine organisms unlock invaluable insights into the Earth’s past environmental conditions and its rotational dynamics. These complex interdisciplinary efforts reaffirm the necessity to monitor and understand Earth’s systemic responses to climate fluctuations, a task increasingly urgent in light of rapid anthropogenic impacts.

By establishing an unprecedented link between ancient climate events and the length of the day, this work catalyzes a shift in how we comprehend Earth as an interconnected system. It calls for a reassessment of long-term rotational models to incorporate climate-driven variables alongside gravitational forces, further refining our understanding of temporal changes in the planet’s behavior.

In summary, the research illuminates the invisible but measurable ways human-induced climate change stretches time itself, however subtly, by adding milliseconds to our days. This revelation offers a profound perspective on the scale of anthropogenic influence and poses important considerations for future scientific and technological adaptations.

News Publication Date:
9-Mar-2026

Web References:
http://dx.doi.org/10.1029/2025JB032161