Media release

From: Springer Nature

Increased polar ice melting due to global warming may be affecting global timekeeping, according to a paper published in Nature. Ice melting in Greenland and Antarctica may have decreased the Earth’s angular velocity (the rate of change of angular position with respect to time) more rapidly than before. As a result, Coordinated Universal Time (UTC) might require a negative 'leap second' three years later than it would otherwise.

Many activities, such as network computing and financial markets, require the consistent, standardized and precise timescale that is provided by UTC. Because the solid Earth’s rotation rate is not constant, UTC has needed to be adjusted since it was defined in 1969 to maintain a consistent time frame with the Earth’s rotation relative to the stars. As the solid Earth’s angular velocity has been decreasing, these adjustments have required a leap second to be added at certain times.

Duncan Agnew used mathematical modelling to investigate the effect of variations of the Earth’s angular momentum on global timekeeping. The angular velocity of the Earth’s mostly liquid core has been decreasing at a constant rate that has steadily increased the angular velocity of the solid Earth (to conserve angular momentum). This effect has resulted in only a few leap seconds being needed over recent decades and, when extrapolated to the future, predicts that a negative leap second will be required as early as the year 2026. Agnew also found, however, that recent increased melting of ice caps in Greenland and Antarctica, measured by satellite gravity, has decreased the solid Earth’s angular velocity more rapidly than before. The author extrapolated these trends to predict the angular velocity of the solid Earth and estimated that UTC, as now defined, will not require a negative leap second until the year 2029. He suggests that this will pose a problem for computer network timing and may require changes in the policy of aligning UTC to the Earth’s rotation to be made earlier than currently planned.

Agnew notes that if polar ice melting had not recently accelerated, the negative leap second would be required three years earlier. He concludes that global warming and global timekeeping have become inextricably linked and may be more so in the future