Climate change is actually making days longer: NPR

Climate change is causing far-reaching global impacts, but now scientists are finding it is changing the planet itself. The rotation of the Earth is slowing down and the length of the day is getting a little longer.

As temperatures rise, huge amounts of ice from Greenland and Antarctica are melting. This meltwater flows into the oceans and redistributes mass closer to the equator. When a planet is thicker around the center, its daily rotation takes slightly longer.

“It is, in a sense, evidence of the severity of climate change,” says Surendra Adhikari of NASA’s Jet Propulsion Laboratory, who authored the study, which was just published. Proceedings of the National Academy of Sciences.

The change is minute, measured in milliseconds, which is one-thousandth of a second. Although this may not be noticeable on a human scale, it can affect the computer systems that control financial transactions, GPS navigation and the electrical grid.

“Everyday life is not sensitive at the one-second level,” says Judah Levine, a physicist at the National Institute of Standards and Technology. “Technology can be and people use it and not realize the sensitivity of it.”

Why don’t days have exactly 24 hours

Clocks measure the day as 24 hours on the nose, but on a highly dynamic planet like Earth, exactly 24 hours is not quite true.

“If you want to be more precise, the length of the day basically changes every day,” says Adhikari. “Today may be a little longer or shorter than yesterday.”

A wide variety of forces are constantly acting on the planet’s rotation. The Moon’s action constantly slows the Earth’s rotation by a few milliseconds per century. The rotation of the solid iron core at the center of the planet can also fluctuate slightly, causing the Earth’s outer layer to speed up or slow down. Even the movement of the Earth’s crust, which is now slowly rebounding after being covered by ice during the last ice age, affects the rotation.

Now, rapidly melting ice at the poles is shifting the planet’s mass and raising ocean levels at the equator. Since 1993, global sea levels have risen an average of 4 inches and are likely to rise 2 feet or more by the end of the century, depending on how much humans reduce climate pollution from burning fossil fuels.

As a result, the Earth is now slightly wider at its center, slowing its rotation much like a spinning figure skater. Skaters with outstretched arms spin more slowly than those with arms drawn to the body. Adhikari and his colleagues found that melting ice has slowed the planet’s rotation by 1.33 milliseconds per century since 2000. If emissions remain high, that will increase to 2.62 milliseconds by the end of the century.

Adding leap seconds

While this amount of time doesn’t mean much for everyday life, it can pose problems for the highly interconnected computer networks that society relies on. GPS and space navigation, as well as financial institutions and cellular networks, all rely on time synchronization. Setting up their clocks can be a major technology headache.

Since 1972, 27 leap seconds have been added to Universal Time to account for the slowing rotation of the Earth. The problem arises because timekeeping is now controlled by atomic clocks, not the rotation of the Earth. However, in order for this time to correspond to the rotation of the planet, seconds had to be added. Tech companies have since rallied against the changes, saying they could cause networks to collapse.

Now experts say climate change will have to be factored into those decisions. But melting ice has far more serious consequences for the planet than time. Millions of people face losing their homes as polar ice melts and sea levels continue to rise.

“If you live in a low-lying coastal area, you don’t have to worry about leap seconds,” says Levine. “That’s the least of your worries. You have much more serious issues to deal with.”