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Summary
Using a remarkable record from a 42,000-year-old kauri tree preserved in a bog, researchers have pieced together a record of the last time Earth's protective magnetic field weakened and its poles flipped—known as the Laschamp excursion—exposing to the world to a bombardment of cosmic rays and, the team suggests, briefly shifting Earth's climate. The record shows the field nearly failed prior to its brief swap, which only lasted 500 years. Combined with an unusually quiet Sun that is believed to have occurred during this time, cosmic rays could have caused a notable drop in stratospheric ozone, shifting wind flows and climate patterns, they suggest. However, ice cores capture no record of a large climate change during this time, which came during a period already known to feature drastic climate swings related to the Atlantic Ocean. And scientists believe it is very premature to connect this event to milestones in human evolution that occurred around that time, such as the demise of the Neanderthals or increase in cave painting—though the link is worth investigating.
