solar spots and milankovitch cycle are all predictable cycles that determine how much sunlight reaches where on earth. greenhouse gasses determine how much heat energy we send back and ice or albido how much we reflect back. I tried to research about a rapid polar shift but could not find a rapid one. just a degree every million years. i looked into this interesting paper that had managed to look at the moving poles over serveral million years. still with their rapid movement of poles was described again in degrees per millions of years.
https://en.wikipedia.org/wiki/Geomagnetic_reversal#Effects_on_biosphere
geomagnetic reversal takes place over 200 years atleast. so far im only seeing that there will be more radiation and charged particles will not be trapped in the magnetic field during the magnetopause and i also read there will be more vulcanic activity. it may also damage our electrical equipment.
i couldnt find about thomas theory?