Everyone on the planet will lose a second during the next several years. According to a new study melting polar ice impacts the Earth’s rotation and time itself.
The Earth’s rotation determines the hours and minutes that make up our days. However, that rotation is not continuous; it can vary somewhat depending on what is happening on Earth’s surface and in its molten core.
These very imperceptible shifts occasionally require the world’s clocks to be changed by a “leap second,” which may seem insignificant but can have a significant impact on computing systems.
A lot of seconds have been added over the years. However, after a long period of slowdown, the Earth’s rotation is presently accelerating due to changes in its core. For the first time, a second will need to be removed.
“A negative leap second has never been added or tested, so the problems it could create are without precedent,” Patrizia Tavella, a member of the Time Department at the International Bureau of Weights and Measures in France, wrote in an article accompanying the study.
Global warming delays leap second addition, pushing from 2026 to 2029
However, when this occurs, it is influenced by global warming, according to a study published Wednesday in the journal Nature. Melting polar ice is postponing the leap second by three years, from 2026 to 2029, according to the paper.
“Part of figuring out what is going to happen in global timekeeping … is dependent on understanding what is happening with the global warming effect,” said Duncan Agnew, professor of geophysics at the University of California San Diego and the study’s author.
Before 1955, a second was defined as a specific fraction of the time it took for the Earth to complete one rotation around the stars. Then came the era of ultra-precise atomic clocks, which proved to be a far more stable method of quantifying physical seconds.
Since the late 1960s, the world has used coordinated universal time (UTC) to establish time zones. UTC uses atomic clocks but still keeps up with the planet’s rotation.
However, because the rotation speed is not constant, the two timelines gradually diverge. This means that a “leap second” must be inserted periodically to bring them back into alignment.
Melting polar ice from fossil fuel emissions slows Earth’s rotation
Over time, the friction of the tides on the ocean floor has slowed the Earth’s rotation. The effects of melting polar ice, caused by people burning planet-warming fossil fuels, have now become a big factor, according to Agnew. As the ice melts into the ocean, meltwater travels from the poles to the equator, slowing the Earth’s rotation.
Ted Scambos, a glaciologist at the University of Colorado Boulder who was not involved in the study, compares the technique to a figure skater spinning with their arms overhead. As they lower their arms to their shoulders, their rotation slows.
Polar ice melt “has been large enough to noticeably affect the rotation of the entire Earth in a way that is unprecedented,” Agnew said. “To me, the fact that human beings have caused the rotation of the Earth to change is kind of amazing.”
