I always thought +/- meant within a range, so if something was +/- 2mm of 4mm it would be from 2mm - 6mm.

I know that's not the point of what you're saying but I learnt something new today too.

This has happened since then and may even be happening right now, w no extinction events.

Original research article from the Adams Event team

Summary Article

Video, “Paleopocalypse!”, narrated by Stephen Fry

Summary:

The temporary breakdown of Earth’s magnetic field 42,000 years ago sparked major climate shifts that led to global environmental change and mass extinctions, a new international study co-led by UNSW Sydney and the South Australian Museum shows.

This dramatic turning point in Earth’s history – laced with electrical storms, widespread auroras, and cosmic radiation – was triggered by the reversal of Earth’s magnetic poles and changing solar winds. The researchers dubbed this danger period the ‘Adams Transitional Geomagnetic Event’, or ‘Adams Event’ for short – a tribute to science fiction writer Douglas Adams, who wrote in The Hitchhiker's Guide to the Galaxy that ‘42’ was the answer to life, the universe, and everything.

Abstract from research paper:

Geological archives record multiple reversals of Earth’s magnetic poles, but the global impacts of these events, if any, remain unclear. Uncertain radiocarbon calibration has limited investigation of the potential effects of the last major magnetic inversion, known as the Laschamps Excursion [41 to 42 thousand years ago (ka)]. We use ancient New Zealand kauri trees (Agathis australis) to develop a detailed record of atmospheric radiocarbon levels across the Laschamps Excursion. We precisely characterize the geomagnetic reversal and perform global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records to investigate impacts. We find that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record.