Global warming is causing glaciers to melt at unprecedented speeds, which in turn is causing sea levels to rise worldwide. Now scientists have confirmed yet another deleterious effect of this process: It is causing the planet's rotation to slow down, according to a new study recently published in Science Advances.
The speed of Earth's rotation is affected by a number of things, such as the shifting behavior of the planet's molten core, and even by a force called tidal acceleration, which is caused by the gravitational dance between Earth and the moon. But the shifting mass of the world's water, as it goes from being frozen as ice to free-flowing in the seas, should also have a measurable effect.
Since human-caused global warming has led to a marked acceleration in sea level rise, especially over the last century, then the Earth's rotational speed should have a correlative change as well. At least, that's been the assumption. But observational data to confirm this correlation have been scant — until now.
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Using a combination of calculations and computer modeling, a team of researchers led by Jerry Mitrovica of Harvard University have finally confirmed the effect. It turns out that Earth’s rotation has slowed by 16,000 seconds, or about 4.5 hours, since 500 B.C. According to Mitrovica's team, 6,000 seconds of this can be blamed specifically on changing sea levels.
Much of the change in sea level during this period of time has been due to the natural process of glacial recession since the last ice age, but the team was able to correct previous miscalculations about the correlation between sea level change and Earth's rotational spin by factoring in updated numbers on 20th century sea level changes, among other things.
It can therefore be expected that as sea levels continue to rise, Earth's rotation will continue to slow down. Although this effect only amounts to a few seconds each year, which is not really perceptible, it further goes to show just how profoundly modern climate change is capable of disrupting our planet.