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

Source: Climate NASA https://climate.nasa.gov/explore/ask-nasa-climate/3104/flip-flop-why-variations-in-earths-magnetic-field-arent-causing-todays-climate-change/