Key points
- Shortest day recorded 1.36 milliseconds under 24 hours
- Climate change slowing Earth’s spin by redistributing mass
- Even millisecond shifts impact satellites and global systems
ISLAMABAD: Scientists and timekeepers have raised concern as Earth’s rotation is speeding up this summer, making days marginally shorter and potentially disrupting global timekeeping systems.
On 10 July, the planet recorded its shortest day of the year so far, 1.36 milliseconds less than the standard 24 hours, according to data compiled by the International Earth Rotation and Reference Systems Service and the US Naval Observatory, according to CNN.
Forecasts show more ultra-short days ahead on 22 July and 5 August, with predicted losses of 1.34 and 1.25 milliseconds respectively.
Earth’s rotation is not perfectly consistent. Influences such as lunar gravity, seasonal atmospheric shifts, and changes in the planet’s liquid core cause daily fluctuations, usually by just milliseconds. While imperceptible to humans, these variations matter significantly in sectors reliant on extreme precision — including satellites, GPS, telecommunications and financial systems.
Atomic clocks
Since 1955, Coordinated Universal Time (UTC) has been calculated using atomic clocks, which are accurate to the billionth of a second. When Earth’s rotation deviates from UTC, “leap seconds” are occasionally added — 27 so far since 1972.
But as Earth speeds up, no leap seconds have been needed since 2016, and the system may soon face an unprecedented reverse adjustment: a “negative leap second,” where a second would be removed.
Experts estimate a 40 per cent chance of this happening before 2035. Such an adjustment has never been attempted and could create technical challenges similar to the Y2K scare, where fears of digital failure arose as clocks ticked from 1999 to 2000.
Seasonal shifts, such as summer atmospheric changes and tidal movements, are short-term contributors to Earth’s faster spin. Over longer periods, the slowing of Earth’s liquid core has also influenced rotational speed.
Counterbalancing effect
Interestingly, climate change is having a counterbalancing effect. Melting ice from Antarctica and Greenland is redistributing mass across the planet, which slows the spin — similar to a figure skater extending their arms. Without this, Earth might already require a negative leap second.
Scientists remain cautious. “We’re still within natural variability,” said Benedikt Soja, a geophysicist in Zurich. “But if warming continues, climate change could overtake lunar forces in influencing Earth’s rotation by century’s end.”
For now, experts are closely monitoring the situation — with even a few milliseconds proving critical to global systems.
