Ilaria Rosella Pagliaro How climate change and melting glaciers affect the Earth's rotation and the measurement of Coordinated Universal Time (UTC), with predictions pointing to the introduction of a negative leap second by 2029
The phenomenon of climate change, commonly linked to the melting of glaciers, carries lesser-known but significantly important implications that affect the geometry and rotational dynamics of our planet, directly influencing the global measurement of time. Changes in the distribution of the Earth’s mass, due to the reduction of polar ice, are indeed altering the shape of the Earth and slowing its rotation speed on its axis, with significant repercussions on Universal Time Coordinated (UTC), the main reference for the definition of world time zones.
A study published in the prestigious journal Nature by the esteemed Duncan Carr Agnew, a professor at the University of California, San Diego, has highlighted how global warming and the melting of ice in Greenland and Antarctica are actually slowing the Earth’s angular velocity. This slow but inexorable deceleration has led scientists to consider for the first time the introduction of a “negative leap second,” i.e., the subtraction of a second rather than its addition, an operation previously scheduled for 2026 but now postponed to 2029 due to these climatic dynamics.
According to Massimo Frezzotti, a glaciologist and professor at Roma Tre University, although the global changes are minimal, they are significant enough to affect Earth’s rotation. Since 1972, UTC has undergone periodic adjustments, adding a total of 27 leap seconds to align atomic time with Earth’s astronomical time, with the last addition made in 2016.
What are the consequences?
Atomic clocks, based on the vibrations of cesium atoms, provide an extremely precise measurement of time, down to the billionths of a second. However, this precision highlights irregularities in the Earth’s rotational movement, such as those induced by tides, emphasizing the daily variability in rotation speed and underlining the need to periodically adjust UTC by introducing the leap second.
The prospect of removing a leap second raises unprecedented and potentially problematic issues for satellite navigation systems and computers. The accuracy of UTC is crucial for the operation of satellite navigation systems like GPS, whose signals are based on extremely accurate time synchronization. A change, even by a single second, can have repercussions on the determination of geographical positions, with potential impacts on transport, telecommunications, and rescue operations.
Similarly, computer networks, which use time synchronization protocols for the security and efficiency of communications, may require updates and technical adaptations to handle variations in UTC. Global financial markets, which depend on millisecond precision in the timing of transactions, could face significant challenges in their daily operations.
Although less immediately apparent, variations in Earth’s rotation can also affect climate models and ecosystems. The distribution and duration of sunlight, for example, can undergo subtle but significant changes that affect the life cycles of plants and animals, potentially altering existing ecological balances.
Agnew’s research, using mathematical models to examine the effect of variations in Earth’s motions on time measurement systems, projects a future in which climate change will continue to increasingly influence our perception and measurement of time.
Source: Nature
