Believe it or not, a team of scientists at Harvard University has published a paper which proves that global warming is slowing the Earth’s rotation. They solved Munk’s Enigma a scientific quandary that was formulated in 2002 by famed oceanographer Walter Munk, and which had stumped climate scientists until now.
Munk had discovered a discrepancy between the amount of sea level rise (SLR) caused by global warming during the 20th century and the effect that the sea level rise should have had on the rotation of Earth. To determine how much the Earth’s rotation has changed over the years, Munk made his calculation by using both 20th century data as well as ancient astronomical records.
One of the things that Munk had to account was a phenomenon called glacial rebound, or the ice age effect. When the Laurentide ice sheet covered North America during the Pleistocene Epoch (2,600,000 to 11,700 years ago), the weight of the glacial ice pushed the land down. But when the ice sheet melted the land below it slowly rose again and this meant that the sea level rose again too. This is phenomenon, which occurred thousands of years ago at the end of the last ice age, is still producing changes on the Earth’s surface, notably in places such as Chesapeake Bay where islands have disappeared due to glacial rebound. The Earth’s rotation is affected by glacial rebound too.
There are in fact two things, science and opinion; the former begets knowledge, the latter ignorance.
Hippocrates (460 BC – 377 BC)
The paper by the scientists at Harvard University was published in the journal Science Advances under the title Reconciling past changes in Earth’s rotation with 20th century global sea-level rise: Resolving Munk’s enigma. The full text of the article is available online.
Munk used three different observations related to Earth’s rotation. His analysis of Babylonian, Chinese, Arab, and Greek eclipse observations from (500 BC to 1600 AD) identified a known slowing of Earth’s rotation rate sufficient to produce a small clock error. His second and third observations involved changes in the magnitude and orientation of the Earth’s rotation, as well as global mean sea-level (GMSL) rise during the 20th century.
But when Munk crunched his numbers, his result did not match the actual measured change in the Earth’s rotation. By his calculations, the effect on the Earth’s rotation caused by the sea level rise caused by climate change should have been higher. In short, his numbers didn’t add up.
The scientists at Harvard discovered why. There were mistakes in the data used by Munk. For example, the estimates Munk used for sea-level rise during the 20th-century were too high. He used data that assumed the rate of sea level rise was about 1.5 to 2 millimeters per year. However, more recent measurements indicate a lower rate of sea level rise, about 1 to 1.5 millimeters per year
When the Harvard scientists inserted those figures into Munk’s calculations, the result was much closer to the change in the Earth’s rotation that has been observed by NASA and other scientific agencies. But, even with the updated sea-level rise estimates, the calculations didn’t quite work, because there was another piece of the puzzle that Munk had missed, and the Harvard Scientists didn’t.
Jerry Mitrovica, the paper’s lead author and a professor of geophysics at Harvard explained it this way. “If you melt ice sheets or glaciers, which happen to be close to the poles, and all of that mass moves from the poles toward the equators, that movement is very similar to a figure skater who puts her arms out. The melting of glaciers acts to slow the spin of the Earth in a measurable way.”
When that effect was factored into Munk’s calculations, the result was an almost perfect match with the scientifically observed changes in the rotation of the Earth. Munk’s Enigma was the work of a genius. But everybody is human and no human is perfect, not even a genius.
Munk’s enigma has been solved. The scientific data now show without a doubt that the global mean sea-level (GMSL) rise caused by global warming has changed the rotation of the Earth. But in all probability, climate change deniers will ignore this scientific evidence just as they have ignored all the other scientific evidence that human activity, especially our reliance on fossil fuels, had had a serious negative effect on Earth’s climate. They may not get the point until New Orleans or Miami disappears under the waves.