Melting polar ice is changing the way the Earth spins and lengthening our days

CNN
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According to new research, the effects of human-caused climate change are so staggering that they are actually messing with time.

The melting of polar ice caused by global warming is changing speed According to a study published Monday in the journal Proceedings of the National Academy of Sciences, the Earth is rotating and increasing the length of each day, a trend that will accelerate this century as humans continue to pump pollution into the warming planet.

The changes are small—a matter of milliseconds a day—but in our high-tech, hyper-connected world, they have an important impact on the computing systems we’ve come to rely on, including GPS.

It’s another sign of the enormous impact humans have on the planet. “This is evidence of the severity of ongoing climate change,” said Surendra Adhikari, a geophysicist at NASA’s Jet Propulsion Laboratory and an author of the report.

The number of hours, minutes, and seconds that make up each day on Earth is determined by the speed of Earth’s rotation, which is affected by a complex knot of factors. These include processes in the planet’s liquid core, the continued impact of the melting of huge glaciers after the last ice age, as well as the melting of polar ice due to climate change.

For millennia, however, the influence of the Moon dominated, extending the length of the day by a few milliseconds per century. The Moon exerts a pull on the Earth that causes the oceans to bulge toward it, gradually slowing the Earth’s rotation.

Scientists have previously made connections between melting polar ice and longer days, but new research suggests that global warming has a greater effect on time than recent studies have shown.

In the past, the impact of climate change on time “wasn’t that dramatic,” said Benedikt Soja, study author and assistant professor of space geodesy at Switzerland’s ETH Zurich.

But that could change. If the world continues to drain planet-warming pollution, “climate change could become the new dominant factor, surpassing the role of the moon. he told CNN.

Here’s how it works: As humans warm the world, glaciers and ice sheets melt, and the melting water flows from the poles towards the equator. This changes the shape of the planet – flattening it at the poles and bulging more in the middle – slowing its rotation.

This process is often compared to a spinning skater. When the skater pulls his arms to his body, he spins faster. But if they move their arms outward, away from their body, their rotation slows down.

An international team of scientists looked at the 200-year period between 1900 and 2100 using observational data and climate models to understand how climate change affected day length in the past and project its role in the future.

They found that the effect of climate change on the length of the day has increased significantly.

Sea level rise caused by climate change caused the length of a day to vary between 0.3 and 1 millisecond in the 20th century. But over the past two decades, scientists calculated an increase in day length of 1.33 milliseconds per century, which is “significantly more than at any time in the 20th century,” according to the report.

If planet-warming pollution continues to rise, warming the oceans and accelerating ice loss in Greenland and Antarctica, the rate of change will increase, the report says. If the world is unable to curb emissions, climate change could increase the length of the day by 2.62 milliseconds by the end of the century – surpassing the natural effects of the moon.

“In barely 200 years, we’re going to change the Earth’s climate system enough to see it impact the very way the Earth spins,” Adhikari told CNN.

A few extra milliseconds a day may be imperceptible to humans, but they have an impact on technology.

Accurate timekeeping is essential to GPS, which everyone with a smartphone will have, as well as other communication and navigation systems. These use highly accurate atomic time, based on the frequency of certain atoms.

Since the late 1960s, the world has started using Coordinated Universal Time (UTC) to set time zones. UTC relies on atomic clocks but still keeps pace with the planet’s rotation. This means that at some point “leap seconds” must be added or subtracted to keep it in line with the Earth’s rotation.

Some studies have also suggested a correlation between increasing day length and an increase in earthquakes, said Mostafa Kiani Shahvandi, study author and geoscientist at ETH Zurich. However, the link remains speculative and much more research needs to be done to establish any clear link, he told CNN.

A work on the same subject published in March has ended that while climate change was increasingly slowing the Earth’s rotation, processes in the Earth’s core may have been more important and actually speeding it up, shortening the length of the day.

“What we’ve done is go a little further and rethink these trends,” Shahvandi said. They found that any effect of the molten core was outweighed by the effect of climate change.

Duncan Agnew, a professor of geophysics at the University of California, San Diego and author of the March study, said the news The study still links to his research, “and is valuable because it extends the result further into the future and looks at more than one climate scenario.”

Jacqueline McCleary, an assistant professor of physics at Northeastern University who was not involved in the study, said the new research helps inform “a decades-long debate about exactly what role climate change will play in the changing length of the day.”

While there is now general agreement that climate change will have a “net day-lengthening effect,” she told CNN, there is still uncertainty about which weather-affecting processes will dominate this century. That study concluded that climate change is now the second most dominant factor, she said.

It’s a sobering conclusion, said ETH Zurich’s Soja. “We have to consider that we are now influencing the orientation of the Earth in space so much that we are dominating effects that have been in action for billions of years.”