Earth's days are getting longer at a speed not seen in at least 3.6 million years. New research shows human-caused climate change is primarily responsible, with melting ice sheets and glaciers slowing the planet's rotation. Days are now lengthening by about 1.33 milliseconds per century, a subtle but significant change impacting global timekeeping and navigation.[iflscience+4]
A Slowing Planet
The planet's spin is gradually slowing down, making each day slightly longer. This change is tiny, adding roughly 1.33 milliseconds to every century. Think of it like a figure skater extending their arms, which causes them to spin slower. Earth's mass redistribution works in a similar way.[iflscience+4]
Scientists from the University of Vienna and ETH Zurich led the recent studies confirming this trend. They found that while Earth's rotation naturally speeds up and slows down, the current rate of lengthening is highly unusual.[iflscience+4]
Climate Change's Role
Human-driven climate change is the main reason for this rapid slowdown. Global warming melts polar ice sheets and mountain glaciers. As this ice turns to liquid, the water spreads across the oceans, moving mass away from Earth's poles and towards the equator.This shift in mass acts like a brake on the planet's rotation.[iflscience+8]
Mostafa Kiani Shahvandi, a study author from the University of Vienna, explained the process. "The accelerated melting of polar ice sheets and mountain glaciers in the 21st century is raising sea levels, which slows Earth's rotation and therefore lengthens the day," he said.He likened it to a figure skater spinning slower when they stretch their arms out.[iflscience+6]
Benedikt Soja, a professor of Space Geodesy at ETH Zurich, highlighted the human impact. "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," Soja stated.He added that "the current rapid rise in day length can thus be attributed primarily to human influences."While the Moon's gravitational pull has always caused a long-term slowdown of Earth's rotation, the current rapid increase is distinct and directly linked to human activity.[iflscience+13]
Unprecedented in Geological History
Researchers used advanced methods to look back millions of years. They studied paleoclimate data, including the fossil remains of tiny single-celled marine organisms called benthic foraminifera.By analyzing the chemical makeup of these fossils, scientists could figure out past sea-level changes. These sea-level changes then allowed them to calculate how Earth's rotation varied over time.[rdworldonline+7]
The findings, published in the Journal of Geophysical Research: Solid Earth, show just how unique the present situation is.Their analysis revealed that only once before, around 2 million years ago, was there a nearly comparable rate of change in day length.However, the current rate of increase remains unparalleled over the past 3.6 million years.[gizmodo+13]
The study also used a new deep learning approach, a "physics-informed diffusion model," to reconstruct Earth's rotational history with high accuracy.This method helped confirm that current changes stand out significantly in Earth's climate history.[rdworldonline+5]
Impact on Modern Life
Even though the changes are only milliseconds, they have real-world implications. Precise timekeeping, which our modern world relies on, is affected.Global systems like GPS satellites and space navigation need extremely accurate information about Earth's rotation.[iflscience+7]
The international standard for time, Coordinated Universal Time (UTC), uses atomic clocks. However, UTC must be regularly adjusted to stay in sync with Earth's slightly changing rotation.This often means adding "leap seconds" to our clocks.[climateadaptationplatform+5]
Benedikt Soja noted that "even though the changes are only milliseconds, they can cause problems in many areas, for example, in precise space navigation, which requires accurate information on Earth's rotation."Some experts believe the slowing rotation might even delay the need for a "negative leap second," which would remove a second from our clocks, a complex adjustment for computer systems.[iflscience+4]
The ongoing research helps scientists understand Earth as a dynamic system. It also shows the far-reaching impact of human activities on the planet's natural processes.Scientists expect these effects to grow stronger as global warming and ice melting continue in the coming decades.[forbes+6]
