Researchers say that day lengthening is ‘unprecedented’, caused by rising sea levels slowing Earth’s rotation
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A new study, published in the Journal of Geophysical Research: Solid Earth, has found that from 2000–2020, each day has lengthened by 1.33 milliseconds due to climate-related factors such as sea level changes. Such a rise, researchers say, is unparalleled across the last 3.6 million years.
To come to their conclusions, researchers from the University of Vienna and ETH Zurich use the fossilised remains of single-celled marine organisms called benthic foraminifera. From the chemical composition of their shells, researchers could deduce clues about past ocean conditions and estimate ancient sea levels.
Their findings were stark: the rise in day length could be primarily attributed to human influences. The analysis did show that historically, day-length changes were recorded – but the modern rate of change is unusually fast.
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How does climate change impact the Earth’s spin?
Earth doesn’t spin at a perfectly constant speed. Its rotation changes due to several factors – historically, other factors such as tidal forces from the moon have been the main influence on this phenomenon. But currently, modern climate change is playing a significant role.
As temperatures rise, glaciers and polar ice sheets melt. This water flows into oceans, adding to rising sea levels and redistributing mass across the planet.
Put simply, the effect that sea level rise has on the rotational spin of Earth can be explained by an analogy of a figure skater. As meltwater from Antarctica and the Arctic spreads from these areas toward the equator, the effect is similar to a figure skater spinning more slowly once they stretch their arms.
By the end of the 21st century, climate change is expected to affect day length even more strongly than the moon. Even though changes are microscopic – occurring in milliseconds – they can cause problems in many areas, for example, in precise space navigation that relies on accurate information about Earth’s rotation. However, these changes are unlikely to impact human biology, such as sleep or circadian rhythms.
If the world continues to warm thanks to greenhouse gas emissions, scientists predict that climate change could increase the length of a day by 2.62 milliseconds by the end of the century.
