As the World Turns
Published: April 25, 2011
Q. Do the shifts of the Earth's axis produced by earthquakes alter world weather?
A. "In short, no," said Allegra N. LeGrande of the Center for Climate Systems Research at Columbia University. "The changes are simply too small."
Researchers at the NASA Jet Propulsion Laboratory calculate that the recent earthquake in Japan pushed the Earth's rotational axis more than 6.5 inches, while the quake in Chile in 2010 shifted it by 2.8 inches, through slightly altering the distribution of mass across the Earth.
But "natural shifts in the Earth's mass in the atmosphere and oceans also cause changes of about 39 inches in the rotational axis each year," Dr. LeGrande said. "In other words, the shifts associated with earthquakes are much smaller than the unnoticeable shifts that occur each year anyhow."
Large shifts in the axis do cause climate changes, Dr. LeGrande said. The cyclical change in the axis tilt associated with astronomical changes, called obliquity, has a very long cycle, about 41,000 years, and changes the tilt from around 22.1 degrees to 24.5 degrees. Right now it is about 23.4 degrees.
At high latitudes, greater obliquity means greater total annual irradiation. At low latitudes, the opposite is true, and at middle latitudes, there is almost no change. When obliquity is high, Dr. LeGrande said, the difference between the equator and the poles in total irradiation, and also in temperature, is larger, and as a result the seasonal cycle becomes more extreme.
"But the changes that occur each year with obliquity are so tiny as to be unnoticeable," Dr. LeGrande said.
C. CLAIBORNE RAYSource
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