Are we about to have a magnetic reversal?

Almost certainly not.

Since the invention of the magnetometer in the 1830s, the average intensity of the magnetic field at the Earth's surface has decreased by about ten percent. We know from paleomagnetic records that the intensity of the magnetic field decreases by as much as ninety percent at the Earth's surface during a reversal. But those same paleomagnetic records also show that the field intensity can vary significantly without resulting in a reversal.

So a reduced intensity in the magnetic field does not necessarily mean that a reversal is about to occur. Moreover, the decrease in intensity is not a dramatic departure from normal. For all we know, the field may actually get stronger at some point in the not-so-distant future.

Predicting the occurrence of a reversal based on the current state of the magnetic field is extremely difficult. Reversals are not instantaneous--they take place over a period of hundreds to thousands of years. We wouldn’t know that a reversal is happening until it was half over. 

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Midcontinent aeromagnetic anomalies
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Aeromagnetic anomalies over part of the Midcontinent rift region

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Attribution: Energy and Minerals
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Attribution: Geomagnetism
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Fredericksburg Geomagnetic Observatory

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Image: Deadhorse Geomagnetic Observatory
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Boulder Geomagnetic Observatory

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The geomagnetic polarity timescale.

The geomagnetic polarity timescale

The geomagnetic polarity timescale.

Image: College Geomagnetic Observatory

College Geomagnetic Observatory

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Chart showing the Earth’s magnetic feild

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