In what researchers see as confirmation that climate change is changing the length of the day on our planet, a new study has shown that Earth's rotation has slowed in recent decades - more than at almost any other time in millions of years.
The rotation is currently lengthening by 1.33 milliseconds per century, making the slowdown not noticeable in everyday life, the reasearchers in Austria and Switzerland say.
Even so, the study said the longer day could affect precise timekeeping and spaceflight navigation, both of which are based on the Earth’s rotation.
At school, pupils are taught that a day lasts 24 hours because the Earth rotates once on its axis in that time. Strictly speaking, however, the duration of Earth’s rotation changes due to the Moon’s gravitational pull and geophysical processes inside Earth, on its surface and in the atmosphere.
In earlier research, Mostafa Kiani Shahvandi of the University of Vienna and Benedikt Soja of ETH Zurich showed that sea levels are rising due to accelerated ice melt at the poles and on glaciers, which in turn slows the Earth's rotation.
This is comparable to a figure skater who spins more slowly when she stretches out her arms, Kiani Shahvandi said in a statement from the University of Vienna.
The researchers then wanted to find out whether there had been earlier phases in which the climate significantly increased the length of the day. To do so, they analysed the chemical composition of marine fossils as an indicator of sea level. They then used mathematical models to derive changes in day length.
The research, published in March, found that the Earth's rotation repeatedly changed over the past 3.6 million years. But only once so far - about 2 million years ago - did the planet slow by roughly as much as between 2000 and 2020. The current lengthening of the day can mainly be attributed to human influences, Soja said.
"What we are observing is caused by climate change," Soja told dpa. Calculations suggest that the globe will slow even more in future as global warming continues. – dpa
