How global warming is literally making your day longer

Solving a scientific mystery over 20 years old, a team of Harvard researchers published a paper proving global warming's role in slowing the Earth's rotation.

NASA/Reuters
The Thwaites Glacier in Antarctica is seen in this undated handout NASA image. The melting of glaciers caused by the world's rising temperatures appears to be causing a slight slowing of the Earth's rotation in another illustration of the far-reaching impact of global climate change, scientists said December 10, 2015.

Melting glaciers caused by global warming will likely impact the Earth’s rotation, researchers suggest in a paper published Friday in the journal Science Advances. 

Researchers at Harvard University suggest the duration of the Earth’s day has lengthened by a millisecond over the past 100 years. Because, as atmospheric temperature rises and ice from the poles melts into the ocean, the weight of the planet’s water shifts from Earth’s axis to the Equator, causing the planet’s rotation to wobble and slow.

And when the Earth’s rotation slows, the days get longer.

“Because glaciers are at high latitudes, when they melt they redistribute water from these high latitudes towards lower latitudes, and like a figure skater who moves his or her arms away from their body, this acts to slow the rotation rate of the Earth,” Harvard University geophysicist and lead author Jerry Mitrovica told Reuters. 

Additionally, glacial melt will make the Earth’s rotation wobble because “the melting of glaciers isn’t perfectly symmetrical, and the water will move more in some parts of the Earth than others,” Mitrovica told The Washington Post.  

Building off of research from a 2002 paper by oceanographer Walter Munk, Mitrovica and his team solved “Munk’s enigma,” an early suggestion that melting glaciers were changing the Earth’s rotation. Dr. Munk knew that the Earth’s rotation had changed, and he knew sea-level rise had occurred, and while he knew the two were related he couldn’t make his data prove it. 

Consequently, Munk predicted that melting polar ice caps would actually make the Earth's days shorter, because melting removes the weight of ice from the poles and allows the underlying rock to rebound upward, adding more mass to the poles and causing the planet to spin more quickly.

But to officially solve Munk’s original thesis, Mitrovica’s team lowered Munk’s estimate of sea level rise over the 20th century by 30 percent (equating to 1 or 1.5 millimeter each year). They also updated Munk’s model to account for Earth’s less-than-perfectly-spherical shape during the Ice Age and underestimating glaciers’ ability to deform underlying rock in the long term. 

And most importantly, Munk did not account for the Earth’s liquid core, which plays a huge role in slowing the planet’s rotation.

“It’s like a hamster in a wheel,” Mathieu Dumberry, a physics professor at the University of Alberta, told CBC news. “The hamster runs in one direction and the wheel [turns] in the other.”

“What we believe in regard to melting of glaciers in the 20th century is completely consistent with changes in Earth’s rotation [as] measured by satellites and astronomical methods,” Mitrovica told Live Science. “By resolving Munk’s enigma, we further strengthen the already-strong argument that we are impacting climate.” 

And while the change is modest, experts say it should not be underrated.

“The period of a day is now a millisecond longer than a century ago but that will accelerate as the melting increases,” Mitrovica told The Guardian. “People won’t be running from their houses screaming about an extra millisecond but it adds yet further confirmation of what we are doing to our environment. It’s another fingerprint.”

The volume of Earth’s glaciers is predicted to decrease between 15 and 85 percent by 2100, further slowing Earth’s rotation. 

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.