The Laschamp event was a short reversal of the Earth's magnetic field. It occurred 41,400 (±2,000) years ago during the last ice age and was first recognised in the late 1960s as a geomagnetic reversal recorded in the Laschamp lava flows in the Clermont-Ferrand district of France.[1] The magnetic excursion has since been demonstrated in geological archives from many parts of the world. The period of reversed magnetic field was ~440 years, with the transition from the normal field lasting ~250 years. The reversed field was 75% weaker whereas the strength dropped to only 5% of the current strength during the transition. This resulted in greater radiation reaching the Earth, causing greater production of beryllium 10 and higher levels of carbon 14.[2]
https://en.wikipedia.org/wiki/Laschamp_event
> Earth's magnetic field, which protects the planet from huge blasts of deadly solar radiation, has been weakening over the past six months, according to data collected by a European Space Agency (ESA) satellite array called Swarm.
The biggest weak spots in the magnetic field — which extends 370,000 miles (600,000 kilometers) above the planet's surface — have sprung up over the Western Hemisphere, while the field has strengthened over areas like the southern Indian Ocean, according to the magnetometers onboard the Swarm satellites — three separate satellites floating in tandem.
The scientists who conducted the study are still unsure why the magnetic field is weakening, but one likely reason is that Earth's magnetic poles are getting ready to flip, said Rune Floberghagen, the ESA's Swarm mission manager. In fact, the data suggest magnetic north is moving toward Siberia. http://www.livescience.com/46694-magnetic-field-weakens.html