Unprecedented for 3.6 million years: Climate change is lengthening our days
Earth's rotation is slowing down faster since the late Pliocene. Days are therefore getting longer by more than a millisecond per 100 years – with consequences.
Days on Earth are getting longer faster than they have in millions of years
(Image: Skylines/Shutterstock.com)
Man-made climate change is slowing down the Earth's rotation as rapidly as no other event in the last 3.6 million years. A research group from Austria and Switzerland has determined this and sees potential impairments in various areas, including satellite navigation. Only two million years ago was the rate of change almost comparable, but apart from that, it has never been comparable in recent Earth history. The lengthening of days by 1.33 milliseconds per century is therefore attributed to the unprecedentedly rapid redistribution of mass between the continents and the oceans.
Like a figure skater
To reconstruct historical and prehistoric day lengths, Mostafa Kiani Shahvandi from the University of Vienna and Benedikt Soja from ETH Zurich examined the fossil remains of single-celled marine organisms. Based on the chemical composition of the shells of so-called benthic foraminifera, the fluctuations in sea level can be traced, and through calculations, the fluctuations in day length can be derived, explains Kiani Shahvandi. A special deep learning algorithm was then used for reliable conclusions. This confirmed that the growth and melting of continental ice sheets have caused major fluctuations in day length. However, the rate from the years 2000 to 2020 is unprecedented.
The two researchers compare the process itself to a figure skater who can influence their rotational speed by extending their arms – and then rotating more slowly – or holding them close to their body. The research group showed in an earlier study that the accelerated melting of polar ice sheets and mountain glaciers is sufficient to slow down the Earth's rotation. However, it was not yet clear how the current rate compares historically and "whether there were also phases in the past when the climate increased day length similarly rapidly," adds Kiani Shahvandi. Now there is a clear indication that "the rate of modern climate change is unprecedented at least since the late Pliocene 3.6 million years ago," adds Soja.
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Even though it is currently only about one millisecond per century, the change in day length can have practical consequences, the researchers write. They primarily refer to precise navigation systems that are based on satellites and require accurate information about the Earth's rotation. However, the researchers cannot say whether its deceleration has or will have concrete consequences. Their work, now published in the Journal of Geophysical Research, once again shows the unexpected consequences of global warming. By the end of the century, climate change will therefore have an even greater impact on day lengths than the moon. And the moon has contributed to stabilizing the rotational speed to today's day length.
(mho)
