It is common knowledge that time is of the essence when it comes to the climate crisis.
A study published Monday found that melting polar ice caps is causing our planet to spin more slowly, making days “unprecedentedly” longer.
The article, published in Proceedings of the National Academy of Sciencesshows that water flowing from Greenland and Antarctica is adding mass around the equator, co-author Surendra Adhikari of NASA’s Jet Propulsion Laboratory told AFP.
“It’s like a figure skater doing a pirouette, where she first holds her arms close to her body and then extends them,” adds co-author Benedikt Soja of ETH Zurich.
“The initially fast rotation slows down as the masses move away from the axis of rotation, increasing the physical inertia.”
The Earth is generally thought of as a sphere, but it is more accurate to speak of an ‘oblate spheroid’ that bulges slightly around the equator, somewhat like a tangerine.
Moreover, its shape is constantly changing, influenced by the daily tides that affect the oceans and the Earth’s crust, as well as by the long-term effects of tectonic plate shifts and sudden, violent shifts caused by earthquakes and volcanoes.
The paper relied on observational techniques such as Very Long Baseline Interferometry, which allow scientists to measure the difference in the time it takes for radio signals from space to reach different points on Earth. From this, they can infer variations in the orientation of the planet and the length of the day.
The Global Positioning System, which measures the Earth’s rotation very accurately, down to about a hundredth of a millisecond, was also used. They even looked at old data on solar eclipses going back thousands of years.
Implications for space travel
As the Earth rotates more slowly, the length of the day increases by a few milliseconds from the standard measure of 86,400 seconds.
A more important cause of the slowdown today is the Moon’s gravity pulling on the oceans. This process is called tidal friction and has caused a gradual slowing of 2.40 milliseconds per century over millions of years.
But the new research comes to the surprising conclusion that if humans continue to emit greenhouse gases at a rapid pace, the effect of a warming climate will be greater than that of the moon’s gravitational pull by the end of the 21st century, Adhikari said.
Between the year 1900 and today, climate has caused the days to lengthen by about 0.8 milliseconds. In the worst case of high emissions, climate alone would be responsible for the days becoming 2.2 milliseconds longer by the year 2100, compared to the same baseline.
That may not seem like much, and it’s certainly not something that humans can perceive.
“But there are certainly a lot of implications for space travel and navigation on Earth,” Adhikari said.
Knowing the exact position of the Earth at any given time is crucial when trying to communicate with spacecraft, such as the Voyager probes now far beyond our solar system. Even a small deviation of a centimeter can cause the probe to be miles off target.
© Agence France-Presse