The Astonishing Reason Why Our Days Are Getting Longer

In the urgent landscape of the climate crisis, time itself is undergoing subtle yet significant changes, as highlighted by a recent study revealing an unprecedented consequence of melting polar ice caps: the lengthening of Earth’s days. Published in the Proceedings of the National Academy of Sciences, the study illuminates how the redistribution of water from Greenland and Antarctica is altering the planet’s rotation speed, gradually increasing the length of our days. Co-author Surendra Adhikari, from NASA’s Jet Propulsion Laboratory, explained that the process is akin to a figure skater extending her arms during a pirouette. As masses shift away from Earth’s rotational axis due to melting ice, they increase the planet’s physical inertia, slowing its rotation. This phenomenon leads to longer days, a concept rooted in Earth’s oblate spheroid shape, where mass distribution affects rotational dynamics.

Earth, often depicted as spherical, actually bulges at the equator, resembling a satsuma fruit. This oblate spheroid shape is not static; it fluctuates under the influence of daily tidal cycles, tectonic plate movements, and seismic events like earthquakes and volcanic eruptions. The study employed advanced techniques such as Very Long Baseline Interferometry and Global Positioning System measurements, precise to a fraction of a millisecond, to track these subtle changes in Earth’s rotation and day length. Currently, the dominant contributor to this rotational slowdown is the Moon’s gravitational pull, causing tidal friction that has gradually lengthened days by approximately 2.40 milliseconds per century over millions of years. However, the study unveils a startling revelation: the influence of climate change, driven by human-induced greenhouse gas emissions, is poised to surpass the Moon’s impact by the end of the 21st century.

Since 1900, climate change has already lengthened Earth’s days by about 0.8 milliseconds, primarily through the redistribution of water masses and associated inertia changes. Under a high-emission scenario, this effect could accelerate, potentially adding 2.2 milliseconds to the day by 2100 compared to pre-industrial levels. While imperceptible to human senses, these changes have profound implications for global navigation systems and space missions. Adhikari underscores the critical importance of precise Earth orientation data for spacecraft navigation, where even minute deviations can lead to significant positional errors over vast distances. This precision is crucial for missions like the Voyager probes, which venture beyond the solar system, relying on accurate Earth orientation data transmitted across vast distances.

Beyond the scientific implications, the study’s findings underscore the interconnected nature of Earth’s systems and the profound impact of human activities on planetary dynamics. As global temperatures rise and ice continues to melt at unprecedented rates, the Earth’s rotational dynamics are undergoing an accelerated evolution, influencing everything from climate patterns to global navigation infrastructure. In conclusion, while the lengthening of Earth’s days may seem subtle, its implications are far-reaching. It serves as a poignant reminder of the intricate balance within Earth’s systems and the urgent need for concerted global action to mitigate climate change. Understanding these dynamics not only enhances our scientific understanding but also underscores the imperative of safeguarding Earth’s delicate equilibrium for future generations.