A new study of previous reversals of Earth's magnetic field has found a rapid shift occurred within two centuries — a discovery that has prompted researchers to warn of a potential dire scenario.
According to a team of international scientists, including from the Australian National University (ANU), such an event in the future would increase our planet's exposure to the Sun's radiation, and could cause trillions of dollars in damage by decimating power and communications systems across the globe.
The Earth has a magnetic field that scientists believe is generated by motion in the planet's core. It's what gives us our north and south poles and powers compasses.
We've known for more than a century that our planet's magnetic field has been weakening at a rate of about five per cent a century, prompting concerns that the Earth's magnetic poles could soon flip — an event that could have potentially disastrous results for life on Earth.
The last time the poles reversed was roughly 780,000 years ago and certain commentators have expressed concern that we could be heading for another flip in the not too distant future. Historically the magnetic north and south poles flip about every 300,000 years, so some say we're overdue.
The new research shows that magnetic field reversals could happen much more rapidly than the thousands of years previously thought to be needed.
Professor Andrew Roberts from the ANU's Research School of Earth Sciences said the magnetic field's strength decreased by about 90 per cent when a field reversal occurred, making the Earth much more vulnerable to the Sun's radiation.
"Earth's magnetic field, which has existed for at least 3.45 billion years, provides a shield from the direct impact of solar radiation," he said in a statement released by the ANU.
"Even with Earth's strong magnetic field today, we're still susceptible to solar storms that can damage our electricity-based society."
From the electrical grids that power our computers to the satellites that let us watch TV, many facets of our lives depend on the Earth's magnetic field. It also acts like an invisible force field protecting Earth from solar winds and harmful cosmic radiation.
A dramatic drop in its strength brought about by a reversal could leave us vulnerable.
The study looked at the paleomagnetic record from 107,000 to 91,000 years ago that is based on precise magnetic analysis and radiometric dating of a stalagmite from a cave in southwestern China.
"The record provides important insights into ancient magnetic field behaviour, which has turned out to vary much more rapidly than previously thought," Prof Roberts said.
The group's findings were published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).
About 40,000 years ago, Earth's magnetic field underwent a dramatic "wobble" but didn't quite topple, researchers believe. But the ongoing weakening and in particular the expansion of a weak hole in the magnetic field in the South Atlantic known as the South Atlantic Anomaly (SAA), has led to concerns that a significant change could be afoot.
However a separate report also published in the PNAS journal back in May downplayed the idea that the poles are reversing.
Prof Roberts said there is no need to panic just yet and hoped we would be able to develop ways to mitigate against the effects of a future pole reversal.
"Hopefully such an event is a long way in the future and we can develop future technologies to avoid huge damage, where possible, from such events," he said.