How Do The Positions Of The Magnetic Poles Change Through Time?

conceptual animation of solar wind — A constant outflow of solar material streams out from the Sun, depicted here in an artist'southward rendering. This solar wind is always passing by Earth. Credit: NASA Goddard's Conceptual Image Lab/Greg Shirah

Earth is surrounded by an immense magnetic field, called the magnetosphere. Generated by powerful, dynamic forces at the center of our world, our magnetosphere shields u.s. from erosion of our atmosphere by the solar wind, particle radiation from coronal mass ejections (eruptions of large clouds of energetic, magnetized plasma from the Sun's corona into space), and from catholic rays from deep space. Our magnetosphere plays the role of gatekeeper, repelling these forms of energy that are harmful to life, trapping almost of it safely away from Earth's surface. You can larn more well-nigh Earth's magnetosphere here.

Since the forces that generate our magnetic field are constantly changing, the field itself is also in continual flux, its strength waxing and waning over time. This causes the location of World'south magnetic north and south poles to gradually shift, and to fifty-fifty completely flip locations every 300,000 years or so. That might be somewhat important if you employ a compass, or for certain animals like birds, fish and ocean turtles, whose internal compasses use the magnetic field to navigate.

Some people have claimed that variations in Earth's magnetic field are contributing to current global warming and tin cause catastrophic climate change. However, the science doesn't back up that argument. In this blog, we'll examine a number of proposed hypotheses regarding the effects of changes in Earth's magnetic field on climate. We'll also discuss physics-based reasons why changes in the magnetic field can't impact climate.

Image of the average strength of Earth's magnetic field at the surface (measured in nanotesla) between January 1 and June 30, 2014

Image showing changes in Earth's magnetic field between January 1 and June 20, 2014 — Launched in Nov 2013 by the European Space Agency (ESA), the three-satellite Swarm constellation is providing new insights into the workings of Earth's global magnetic field. Generated by the motion of molten fe in Earth's core, the magnetic field protects our planet from cosmic radiation and from the charged particles emitted by our Sun. It as well provides the basis for navigation with a compass.
Based on data from Swarm, the top image shows the boilerplate strength of Earth's magnetic field at the surface (measured in nanotesla) between January 1 and June xxx, 2014. The second paradigm shows changes in that field over the aforementioned menstruation. Though the colors in the second prototype are just equally vivid as the first, note that the greatest changes were plus or minus 100 nanotesla in a field that reaches 60,000 nanotesla. Credit: European Space Agency/Technical University of Denmark (ESA/DTU Space)

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Hypotheses:

1. Shifts in Magnetic Pole Locations

The position of Earth'due south magnetic north pole was showtime precisely located in 1831. Since then, it's gradually drifted north-northwest by more than 600 miles (1,100 kilometers), and its forward speed has increased from about x miles (16 kilometers) per year to about 34 miles (55 kilometers) per year. This gradual shift impacts navigation and must be regularly deemed for. However, there is picayune scientific bear witness of any significant links between Earth's drifting magnetic poles and climate.

2. Magnetic Pole Reversals

Supercomputer models of Earth's magnetic field. On the left is a normal dipolar magnetic field, typical of the long years betwixt polarity reversals. On the right is the sort of complicated magnetic field Globe has during the upheaval of a reversal. Credit: Academy of California, Santa Cruz/Gary Glatzmaier

During a pole reversal, Earth's magnetic north and s poles bandy locations. While that may sound like a big deal, pole reversals are common in Earth's geologic history. Paleomagnetic records tell usa Earth'southward magnetic poles have reversed 183 times in the last 83 million years, and at least several hundred times in the past 160 million years. The time intervals between reversals have fluctuated widely, merely average almost 300,000 years, with the last one taking place about 780,000 years ago.

Geomagnetic polarity over the past 169 million years, trailing off into the Jurassic Quiet Zone. Dark areas denote periods of normal polarity, light areas denote reverse polarity. — Geomagnetic polarity over the by 169 million years, trailing off into the Jurassic Tranquillity Zone. Nighttime areas denote periods of normal polarity, low-cal areas denote reverse polarity. Credit: Public domain

During a pole reversal, the magnetic field weakens, but it doesn't completely disappear. The magnetosphere, together with Earth's atmosphere, keep protecting World from cosmic rays and charged solar particles, though there may be a pocket-size amount of particulate radiation that makes it downward to Earth's surface. The magnetic field becomes jumbled, and multiple magnetic poles can emerge in unexpected places.

No one knows exactly when the side by side pole reversal may occur, but scientists know they don't happen overnight: they take identify over hundreds to thousands of years.

In the by 200 years, Earth's magnetic field has weakened about ix percent on a global average. Some people cite this as "evidence" a pole reversal is imminent, but scientists have no reason to believe then. In fact, paleomagnetic studies show the field is about every bit strong as it's been in the past 100,000 years, and is twice as intense as its one thousand thousand-year boilerplate. While some scientists estimate the field's strength might completely disuse in nigh 1,300 years, the current weakening could finish at any time.

The Sun expels a constant outflow of particles and magnetic fields known as the solar wind and vast clouds of hot plasma and radiation called coronal mass ejections. This solar material streams across space and strikes Earth's magnetosphere, the space occupied by Earth's magnetic field, which acts like a protective shield around the planet. — The Sun expels a constant outflow of particles and magnetic fields known as the solar current of air and vast clouds of hot plasma and radiation called coronal mass ejections. This solar cloth streams across space and strikes Globe's magnetosphere, the infinite occupied by Earth'due south magnetic field, which acts like a protective shield around the planet. Credit: NASA Goddard/Bailee DesRocher

Constitute and animal fossils from the period of the last major pole reversal don't prove any large changes. Deep ocean sediment samples signal glacial activity was stable. In fact, geologic and fossil records from previous reversals show goose egg remarkable, such as doomsday events or major extinctions.

three. Geomagnetic Excursions

Recently, at that place accept been questions and discussion almost "geomagnetic excursions:" shorter-lived but significant changes in the magnetic field'southward intensity that concluding from a few centuries to a few tens of thousands of years. During the last major circuit, called the Laschamps event, radiocarbon evidence shows that near 41,500 years ago, the magnetic field weakened significantly and the poles reversed, only to flip back once again near 500 years later.

While in that location is some evidence of regional climate changes during the Laschamps event timeframe, ice cores from Antarctica and Greenland don't testify any major changes. Moreover, when viewed within the context of climate variability during the terminal ice age, whatsoever changes in climate observed at Earth'southward surface were subtle.

Lesser line: At that place's no bear witness that Globe's climate has been significantly impacted by the last three magnetic field excursions, nor past any excursion issue within at least the last 2.viii million years.

Physical Principles

one. Insufficient Energy in Earth'southward Upper Atmosphere

Electromagnetic currents exist inside Earth's upper temper. But the energy driving the climate system in the upper atmosphere is, on global average, a infinitesimal fraction of the free energy that drives the climate arrangement at Earth's surface. Its magnitude is typically less than ane to a few milliwatts per square meter. To put that into context, the energy budget at Earth's surface is well-nigh 250 to 300 watts per square meter. In the long run, the free energy that governs Earth's upper atmosphere is about 100,000 times less than the amount of free energy driving the climate organization at Earth'southward surface. There is only not enough energy aloft to have an influence on climate down where we live.

two. Air Isn't Ferrous

Finally, changes and shifts in Globe'due south magnetic field polarity don't impact conditions and climate for a key reason: air isn't ferrous.

Ferrous? Say what?? Bueller? Bueller?

Ferrous means "containing or consisting of iron." While fe in volcanic ash is transported in the temper, and small quantities of iron and iron compounds generated by man activities are a source of air pollution in some urban areas, iron isn't a significant component of Earth'south atmosphere. There's no known concrete machinery capable of connecting atmospheric condition conditions at World'due south surface with electromagnetic currents in space.

Thermal and compositional structure of the atmosphere. The upper atmosphere, comprising the mesosphere, thermosphere, and embedded ionosphere, absorbs all incident solar radiation at wavelengths less than 200 nanometers (nm). Nigh of that captivated radiation is ultimately returned to space via infrared emissionsfrom carbon dioxide (CO₂) and nitric oxide (NO) molecules. The stratospheric ozone layer absorbs radiation between 200 and 300 nm.
The plot on the left shows the typical global-boilerplate thermal structure of the atmosphere when the flux of solar radiation is at the minimum and maximum values of its xi-year cycle. The plot on the right shows the density of nitrogen (N2), oxygen (O2), and atomic oxygen (O), the 3 major neutral species in the upper atmosphere, along with the complimentary electron (e−) density, which is equal to the combined density of the diverse ion species. The F, E, and D regions of the ionosphere are also indicated, equally is the troposphere, the atmosphere's lowest region. Credit: Naval Research Laboratory/J. Emmert

Solar storms and their electromagnetic interactions merely affect Globe'due south ionosphere, which extends from the everyman edge of the mesosphere (about 31 miles or 50 kilometers above Earth's surface) to infinite, around 600 miles (965 kilometers) above the surface. They accept no impact on Earth's troposphere or lower stratosphere, where Earth's surface weather, and subsequently its climate, originate.

In short, when information technology comes to climate, variations in Earth's magnetic field are naught to get charged up about.

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