Earth's rotation slower

Climate change makes the days slightly longer

The climate has a tiny influence on the Earth's rotation, which can be measured using modern satellites.

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According to a study, climate change is leading to a minimal lengthening of the Earth's days. As the polar ice melts, the mass in the world's oceans is redistributed, which slows down the Earth's rotation. The climate-related influence on the length of the day is currently around 1.33 milliseconds per century.

This is reported by a research team in the journal "Proceedings" of the US National Academy of Sciences ("PNAS"). 

"Tugging" of the moon against the earth slows down the earth's rotation
If climate change is not curbed, the effect could be greater than the moon's influence on the Earth's rotation, explains the group led by Mostafa Kiani Shahvandi from ETH Zurich. The moon's gravity creates tidal forces on the Earth, which are mainly visible in high and low tides. The moon's "tugging" on the earth minimally slows down the earth's rotation and thus lengthens the day.

The climate also has a tiny influence on the Earth's rotation, which can be measured using modern satellites. 

Increase in day length fluctuates
The researchers' calculations showed that the climate-related increase in day length has fluctuated considerably over the course of the 20th century: between 0.31 milliseconds per century (1960 to 1980) and 1.00 milliseconds per century (1920 to 1940).

For the first two decades of the 21st century, the researchers calculated an average climate-induced increase in day length of 1.33 milliseconds per century - statistically significantly more than in the entire 20th century. 

"Through their effect on day length, these results show that the mass transport from the poles to the equator as a result of climate change has been unprecedented in the last two decades compared to the previous 100 years," say the researchers.

Mass shifts in the Earth's mantle
The effect that counteracts the displacement of the water masses in the course of the ice melt was also taken into account: mass displacements in the Earth's mantle. Kilometre-thick ice pushes the land masses of Greenland and Antarctica into the viscous part of the Earth's mantle on which the Earth's plates move. When the ice melts, the land masses become lighter and rise because viscous earth mantle mass flows underneath. According to calculations, the effect is currently minus 0.8 milliseconds per century, i.e. it shortens the length of the day.