Our days are getting longer.
It’s a consequence of climate change that you would never feel, but scientists say it matters more than you might think.
Rising sea levels caused by melting glaciers and polar ice sheets are slowing Earth’s rotation, adding approximately 1.33 milliseconds to the length of a day every century, according to a new study.
The researchers from the University of Vienna and ETH Zurich also found that this rate of change has not occurred in the last 3.6 million years.
HOW DOES MELTING ICE MAKE DAYS LONGER?
The mechanism behind this is surprisingly intuitive.
As polar ice sheets and mountain glaciers melt in the 21st century, rising sea levels redistribute mass across the planet’s surface, which slows Earth’s rotation and therefore lengthens the day. It’s similar to a figure skater who spins more slowly once they stretch their arms outward.
Earth doesn’t spin at a perfectly constant speed. In fact, the planet’s rotation can shift due to the gravitational pull of the Moon, movements inside the planet, and atmospheric conditions.
But what makes this finding alarming is that human-driven climate change has now become a dominant force in that equation.
To reconstruct how Earth’s rotation has changed over millions of years, the researchers used fossil remains of a tiny single-celled marine organism called benthic foraminifera, whose chemical composition reveals past sea-level fluctuations, from which they mathematically derived corresponding changes in day length.
They also used a deep-learning model to handle the large uncertainties in ancient climate data.
DOES IT MATTER?
The changes are tiny in human terms, but their consequences are real.
Even small shifts in Earth’s rotation can cause problems in areas like space navigation, GPS systems, atomic clock synchronisation, and satellite tracking.
By the end of this century, climate change is expected to have more influence over the length of day than the Moon itself, according to Benedikt Soja, the study’s senior author and a geophysicist at ETH Zurich.
“The current rapid rise in day length can thus be attributed primarily to human influences,” Soja said.
The findings add yet another dimension to the cascading effects of climate change.
The same melting ice that is raising the sea levels across the planet, putting millions at risk, and changing the weather systems, is now also altering the planet’s spin.
It is a stark reminder of how deeply interconnected our climate crisis truly is.
