Ok, let's quickly google and quote some facts from here and there (instead of paranoid hear-say)
The fluxuations in the magnetic field we see today are very very low compared to what the earth's magnetic field has done in the past.
Sometimes the field completely flips. The north and the south poles swap places. Such reversals, recorded in the magnetism of ancient rocks, are unpredictable
and they come at irregular intervals averaging
years; the last one was 780,000
(thus not like stated in the first post every 750,000-780,000 years).
Some reversals occurred within a few 10,000 years of eachother and there are other periods where no reversals occurred for tens of millions of years
No one knows
if we are overdue or not as it is based upon chaos in the core influenced by the surface movements of the earth.
Hence why I said it is the same as point 5...
The ongoing 10% decline since a few decades doesn't mean that a reversal is imminent at all. The field is increasing or decreasing all the time
. Earth's present-day magnetic field is, in fact, much stronger
than normal, although decreasing. The dipole moment, a measure of the intensity of the magnetic field, is now 8 × 1022 amps × m2. That's twice the million-year average of 4× 1022 amps × m2.
Reversals take, at least, a few thousand
years to complete (this alone makes the prediction of 2012 totally rediculus), and during that time, contrary to popular belief, the magnetic field does not completely vanish
, it just gets more complicated with more than one south and one north pole.
Magnetic lines of force near Earth's surface become twisted and tangled, and multiple magnetic poles will pop up in unaccustomed places. A south magnetic pole might emerge over Africa, for instance, or a north pole over Tahiti. Weird. But it's still a planetary magnetic field, and it will still protects us from space radiation and solar storms
. Even if the magnetic field completely vanishes, there are still meganisms which will protect us. The first human beings, homo erectus survived many reversals (otherwise we wouldn't be here). There is in fact no evidence at all that anything went extinct because of a reversal.
sources: stuff like Nature, NGC, SC