Earth’s magnetic poles are on the move. The North Magnetic Pole is moving from northern Canada towards Siberia at a rate of between 34 and 37 miles per hour, and its speed is increasing. At the beginning of the 20th century, it only moved at about 6 miles per year. Now it is shifting north about 1 degree every 5 years. Airports from Tampa to Paris have been forced to renumber their runways, which are aligned to the Earth’s magnetic field for compass purposes.
At the same time, the Earth’s magnetic field is becoming weaker. This is also accelerating. Over the past 150 years, it has declined by about 10-15%. The Earth’s magnetic field is now about 35% weaker than it was at its maximum modern level, about 2,000 years ago. It’s still within the normal range of fluctuation, but it could also be leading up to a geomagnetic reversal, where the Earth’s north and south magnetic poles change sides.
The National Ocean and Atmospheric Administration (NOAA) has warned that the US electrical grid is vulnerable to the effects of a major solar storm. These effects could be even more serious if the magnetic field continues to weaken. Widespread loss of communications or electricity could be life-threatening. An airline disaster caused by faulty communications and electrical blackout could easily kill over a thousand people.
However, there is no evidence that changes to the Earth’s magnetic field will cause atmospheric superstorms, such as massive hurricanes or tornado outbreaks. The magnetic field may have a small effect on weather, but not to that extent.
In the past
Previous reversals have been recorded in the Earth’s geological history. When a rock containing ferromagnetic materials is formed, it records the direction of the magnetic poles for all time. Scientists first found out about magnetic pole reversals by discovering volcanic rocks which were magnetized in the opposite direction from Earth’s magnetic field.
The Cande and Kent Geomagnetic Polarity Time Scale records 184 polarity reversals during the last 83 million years. Other versions of the GPTM go back even farther than that, nearly twice as far. However, older reversals are more difficult to date accurately because the magnetic record in sedimentary rocks can be overwritten.
There is no pattern to the time interval between magnetic pole reversals. Sometimes the magnetic field is constant for as long as 30 to 50 million years, a so-called superchron period. Sometimes it has also flipped after less than 50,000 years. It has been 780,000 years since the most recent flip, the Brunhes-Matuyama reversal.
According to the geologic record, some previous reversals have taken up to 10,000 years to complete. Some have taken as few as 1,000 years to complete. Some evidence indicates that the Brunhes-Matuyama reversal may have happened even faster than that.
During a polarity reversal, the magnetic field weakens, but it does not go completely away. Instead, it forms many localized magnetic fields all over the Earth until it eventually sorts itself out.
Cracks in the magnetic field
The Earth’s magnetic field also has cracks in it, which can be the size of California or even larger. These cracks have been detected since 1979, although they were predicted much earlier. Some cracks remain open for hours at a time.
Cracks can occur whenever the magnetic field of the solar wind is opposite the magnetic field of the Earth. If Earth’s magnetic field is weakening, the cracks may be larger and may open for longer.
The effects of these cracks are felt mostly in the Earth’s upper atmosphere. Usually the only noticeable effect is a localized aurora. However, a localized influx of solar ions could potentially affect atmospheric moisture, because water is a polarized molecule. In turn, this could affect troposphere wind patterns.
Space “weather” is magnetic. Most of Earth’s space weather comes from the sun. Large solar flares can cause magnetic storms on Earth, which result in brilliant auroras near the magnetic poles. Particularly powerful solar flares can overwhelm the Earth’s magnetic field and disrupt communications. Satellites in geosynchronous orbit are especially vulnerable, because a strong solar flare will push Earth’s magnetic field too far inwards to protect them.
The only confirmed magnetic superstorm in human history occurred on September 1 and 2, 1859. It started with a solar flare which was so intense that the amount of sunlight briefly doubled. When the solar particles from the flare reached Earth, they were in opposite alignment with the Earth’s magnetic field and were strong enough to overwhelm it. Auroras were visible as far south as Hawaii, with the New York Times reporting that in Boston, the aurora was “so brilliant that about one o’clock ordinary print could be read by [its] light.”
The auroral current was strong enough to short out most telegraph wires and even cause fires. Some telegraph operators were even able to cut off their battery power and communicate using only the electrical power of the aurora.
This is the strongest magnetic storm that occurred in historic times. Throughout its duration, there were no reports in the media of particularly bad weather. In fact, the skies must have been clear in most parts of the United States. Otherwise, the auroras would not have been so noticeable.
The magnetic storm of 1989 was much less powerful, but it still caused the Hydro-Quebec power grid in Canada to go down for over 9 hours. A 1994 magnetic storm damaged 2 communications satellites and disrupted communications across Canada. The strongest magnetic effects of any solar storm are usually felt in Canada because it is the country which currently contains the North Magnetic Pole.
The current solar cycle is on the upswing. However, it is forecast to be among the weaker solar cycles in known history. A solar storm is always possible, but it probably won’t be a big one. Even so, FEMA estimates that a solar superstorm could occur once every 100 years. The electrical grid in the United States is 10 times as large as it was just 50 years ago, and needs to be ready.
Atmospheric weather caused by changes in magnetism
The strength of Earth’s magnetic field has been linked to the amount of precipitation in the tropics. When galactic cosmic rays get through Earth’s magnetic field to reach the Earth’s atmosphere, they may trigger cloud formation. Some studies have also shown that the strength of Earth’s magnetic field can affect air pressure in the troposphere.
However, these effects are not strong enough to cause atmospheric superstorms by themselves. However, they could potentially intensify storms which are already strong due to other factors.
A storm does not need to be a superstorm to kill hundreds or even thousands of people. All strong storms should be treated with respect. The late-April tornado outbreak across the southeastern United States killed nearly 400 people and caused catastrophic flooding in its wake. A Category 4 hurricane which struck Bangledesh in 1991 killed over 138,000 people, due almost entirely to a strong storm surge onto low-lying land.
What won’t happen
Fortunately for life on earth, magnetic superstorms and flipflops in the Earth’s magnetic field won’t increase the amount of ultraviolet or X-ray radiation which reaches the ground. The magnetic field only affects charged particles, not electromagnetic radiation such as ultraviolet light. That type of radiation is absorbed by the atmosphere, especially the ozone layer, and the ozone layer is also not affected by changes in magnetism.
Magnetic pole reversal won’t affect Earth’s rotation. Wobbles by the Earth’s axis may be influenced by the molten core, but that influence depends on shifts in mass, not shifts in magnetism.
It is extremely unlikely that even a magnetic pole reversal will directly cause life-threatening disruption to life on earth. Homo erectus was already around during the the Brunhes-Matuyama reversal, so clearly humanity survived before. No study has ever found a link between magnetic pole reversals and mass extinction events.