Global Warming Has Even Slowed Earth's Rotation Speed

A study has found that global warming is altering the Earth's rotation speed, which could also affect human timekeeping.

On the 27th (local time), foreign media including AFP and AP reported that a research team led by Duncan Agnew from the University of California published a study in the journal Nature revealing that the Earth's rotation speed is slowing down more than previously predicted due to melting ice in polar regions.

The research team explained that as ice melts from polar glaciers due to climate change, the water flows toward the equator, making the Earth's shape closer to a perfect sphere and slowing its rotation speed. This is similar to the principle where a spinning figure skater slows down when lowering their arms from above their head to their shoulders. The team stated that to correct errors caused by changes in rotation speed, the world time will be artificially advanced by one second around 2029.

The length of a day is measured based on the Earth's rotation period, but the rotation speed varies slightly due to various complex natural phenomena. Because of this, differences arise between atomic time (measured by atomic clocks) and astronomical time (based on astronomical phenomena). To address this, the International Bureau of Weights and Measures (BIPM) introduced the concept of a "leap second" in 1972. Similar to a leap month that occurs every few years, when the accumulated time difference due to changes in rotation speed reaches 0.9 seconds or more, one second is added or subtracted at the end of the year or on June 30 to align the time. Since its introduction in 1972, leap seconds have been applied 27 times, all of which have been positive leap seconds adding one second.

However, recently, due to unknown causes within the Earth's interior, the Earth's rotation speed has been gradually increasing, and for the first time in history, a negative leap second subtracting one second was expected to be implemented in 2026. The research team explained that the involvement of the artificial factor of global warming has delayed the introduction of the negative leap second from 2026 to 2029.

Although leap seconds are too brief for us to perceive, they can have significant impacts on computer systems requiring precise time settings, such as stock trading and satellite navigation. Especially since a negative leap second is unprecedented, many computer programs will need to be reconfigured, and there is a risk of unforeseen errors. Therefore, it is reported that some view the delay of the negative leap second due to global warming as a welcome development.

Professor Agnew of the research team said, "It is astonishing that humans have altered the Earth's rotation." Chris Hughes, a climatologist at the University of Liverpool in the UK, told the Financial Times, "This study is a very clear indicator that significant changes are occurring on Earth."