Global warming interferes with the calculation of universal time – 03/27/2024 – Science

The melting of ice in Greenland and Antarctica changes the Earth’s rotation speed faster than expected, to the point of affecting the calculation of universal time, which determines the proper functioning of computer networks, points out a study released this Wednesday (27 ).

Since 1967, Coordinated Universal Time (UCT) has been established using ultra-sensitive atomic clocks, which keep time around the world and ensure the accuracy of digital and communications infrastructures such as satellite navigation.

For historical reasons, synchrony was maintained between the UCT and astronomical time, calculated from the Earth’s rotation speed, which is not constant. From 1972 onwards, it was decided to compensate for irregularities by adding intercalary seconds to atomic time, so that it coincided with astronomical time.

Intercalary seconds are inserted each time the lag between the two measurements approaches 0.9 seconds. The last adjustment dates back to 2016, according to Duncan Agnew of the Geophysics Institute at the University of California, San Diego. He is the author of one of the studies on the topic, published in the journal Nature.

The acceleration of the Earth’s rotation movement, however, brings an inverse problem, as it will cause astronomical time to come before atomic time, which would force the introduction of a negative intercalary second within a few years.

The news worries metrology experts, since the introduction of a negative intercalary second would bring “unprecedented problems in an increasingly connected world”, says Patrizia Tavella, from the International Bureau of Weights and Measures (BIPM), in a comment study annex.

The uncertainty comes from the fact that computer programs that integrate leap seconds “assume that they are always positive,” according to Agnew.

Earth slows down

Partly because of this new situation, metrologists around the world agreed to suppress the intercalary second by 2035. From that year onwards, it was planned to allow the difference between atomic time and the Earth’s rotation to increase to one minute.

According to Nature, however, this schedule could be compromised by global warming, due to the acceleration of melting in Greenland and Antarctica, which Agnew measured with satellite observations.

Since the 1990s, the melting of ice has slowed down the Earth’s rotation, as have the tides caused by the gravitational force that the Moon and the Sun exert on the planet, counterbalancing the natural acceleration.

“When the ice melts, water spreads throughout the ocean, which alters the distribution of fluids on the Earth’s surface and interior,” says the scientist.

The slowdown effect caused by melting ice was suggested at the end of the 19th century and has been measured since the 1950s, highlights Agnew. “The novelty of my work is to show the extent of the impact of melting ice on the Earth’s rotation, a change never seen before.”

The slowdown is such that it could delay an eventual transition to negative second until 2029, according to forecasts. Without the impacts of global warming, this would likely occur in 2026.

This postponement gives metrologists a breather, who will have “more time to decide whether 2035 is the best date to suppress the interim second or whether it should be abandoned sooner”, commented Patrizia Tavella.