Mar 27, 2024 - Energy & Environment

Study: Climate change has delayed a time conundrum

Illustration of a clock with disappearing earth on its face

Illustration: Sarah Grillo/Axios

Accelerated polar ice melting from human-caused global warming has delayed an upcoming risk to universal standard time by slowing down Earth's rotation, according to a new study published in the journal Nature on Wednesday.

The big picture: The findings suggest the world's timekeepers have longer to manage a first-of-its-kind time adjustment that could wreak havoc on computer networks.

What's inside: The study by University of California San Diego geophysics professor Duncan Agnew published Wednesday found increased tidal friction due to accelerated sea-level rise from polar ice melt has counteracted the effect of changes in Earth's core that are speeding up the planet's rotation.

  • This sea-level-rise break has generated slightly more time to figure out how to manage negative leap seconds. Without the added friction from the tides, the world likely would have had to address the timekeeping problem as soon as 2026.
  • But if current trends continue, Coordinated Universal Time (UTC), the world's primary time standard for decades, should require a negative second by 2029.

How it works: UTC is based on the time kept by hundreds of atomic clocks worldwide but is periodically adjusted with leap seconds to keep it closely aligned with Earth's rotation.

  • These rare additional seconds (so far, there have been 27 since 1972) are needed because atomic clocks consistently count exactly 86,400 seconds every day, but for decades, the Earth's spin had been slowing, making some days longer than others.
  • If ignored, the small millisecond deviation between atomic clocks and Earth's rotation would have snowballed into a large time discrepancy that could have made astronomical observations more difficult while adding confusion to air and sea navigation and telecommunications.
  • But it's been tricky to predict when exactly these adjustments are needed and even tricker to add them to computer networks without causing crippling glitches and widespread disruptions.

Yes, but: The Earth has suddenly begun spinning faster in recent years, partly because the spin of the planet's inner core has slowed.

  • This abrupt acceleration has made days slightly shorter than in the past. That's concerned the world's timekeepers because it presents an unprecedented predicament: having to subtract time to keep atomic clocks in sync with Earth's rotation.

Threat level: Though compensating for an extra second has become relatively common, the impact of removing time is unpredictable and "expected to create many difficulties," the paper said.

  • The effect of negative leap seconds has never been tested on a large scale, and it could have a "devastating effect" on critical digital infrastructure, Meta said as part of a call to end leap seconds.

The intrigue: The study's 2029 forecast suggests that the international bodies that manage time may have to make more immediate changes to UTC if they want to avoid a negative time discontinuity.

  • Currently, international timekeepers are working out how to keep UTC tethered to the Earth's rotation while limiting disruptions from time adjustments.

Zoom out: The General Conference on Weights and Measures (CGPM), the world's supreme authority on measurements, voted in 2022 to discontinue leap seconds in or before 2035.

  • Its decision means the time difference between atomic time and the Earth's spin will one day be allowed to expand beyond a second, but CGPM has yet to decide on a new discrepancy maximum.
  • Some researchers have suggested letting atomic time diverge from solar time for up to a minute before resyncing every half-century or so.

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