A recent study suggests that climate change is altering the Earth’s rotation speed, potentially affecting timekeeping.
The accelerated melting of ice from Greenland and Antarctica is redistributing mass in the world’s seas, slightly slowing down the Earth’s rotation, though it still spins faster than before.
Consequently, global timekeepers might need to subtract a second from clocks later than anticipated.
“This phenomenon impacts Coordinated Universal Time (UTC), calculated based on Earth’s rotation, which isn’t constant due to changes in the liquid core.”
Since the 1970s, about 27 leap seconds have been added to UTC, but a negative leap second might be required for the first time in 2026.
Duncan Agnew, the author of the study and a geophysicist at the Scripps Institution of Oceanography at the University of California, says the ice melting in Greenland and Antarctica has changed where the Earth’s mass is concentrated.
However, the study suggests that accelerated ice melt has offset some of this acceleration, delaying the need for a negative leap second until 2029. This unprecedented event poses challenges for global timing infrastructure and computer systems, as many programs assume leap seconds are always positive. While some skepticism exists regarding the study’s findings, it underscores the impact of human-induced climate change on Earth’s systems, including its rotation and timekeeping.
Experts are concerned that the introduction of a negative leap second, a minute with only 59 seconds, into standard time could disrupt computer systems worldwide.
Historically, time was measured by the Earth’s rotation, but in 1967, timekeepers adopted atomic clocks, which use atomic frequency for more precise timekeeping. However, some, including sailors navigating by the stars, wanted to maintain the link between Earth’s rotation and time.
What Is Compromised?
The challenge arose because the Earth’s rotation was slightly slower than atomic time, necessitating a compromise. When the difference between the two measurements approached 0.9 seconds, a “leap second” was added to Coordinated Universal Time (UTC), the globally accepted standard. Although many people may not have noticed, 27 leap seconds have been added to UTC since 1972, with the last occurring in 2016.
