Climate change is even messing with how we measure time, says study



PARIS: Struggle to wrap your head around daylight savings? Spare a thought for the world’s timekeepers, who are trying to work out how climate change is affecting Earth’s rotation – and in turn, how we keep track of time. In a strange twist, global warming could even help out timekeepers by delaying the need for history’s first “negative leap second” by three years, a study published on Wednesday suggested.Experts fear that introducing a negative leap second – a minute with only 59 seconds – into standard time could cause havoc on computer systems across the world.
For most of history, time was measured by the rotation of the Earth. However in 1967, the world’s timekeepers embraced atomic clocks – ushering in a more precise era of timekeeping. But sailors, who still relied on the Sun and stars for navigation, and others wanted to retain the connection between Earth’s rotation and time. There was a problem. Our planet is an unreliable clock, and had long been rotating slower than atomic time, meaning the two measurements were out of sync. So a compromise was struck. Whenever the difference between the two measurements approached 0.9 of a second, a “leap second” was added to Coordinated Universal Time (UTC), the internationally agreed standard by which the world sets its clocks.
Though most people likely have not noticed, 27 leap seconds have been added to UTC since 1972, the last coming in 2016. But in recent years a new problem has emerged that few saw coming: Earth’s rotation has been speeding up, overtaking atomic time. This means that to bring the two measurements in sync, timekeepers may have to introduce the first ever negative leap second. “This has never happened before, and poses a major challenge to making sure that all parts of the global timing infrastructure show the same time,” said Duncan Agnew, a researcher at the University of California.
He determined that if not for climate change, a negative leap second might have needed to be added to UTC as soon as 2026. But starting from 1990, melting ice in Greenland and Antarctica has slowed down the Earth’s rotation, the study said. This has delayed the need for a negative leap second until at least 2029, it added. Demetrios Matsakis, ex-chief scientist for time services at US Naval Observatory who was not involved in the study, said he was sceptical of Agnew’s analysis.


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