When the dipole moment is strong, carbon-14 production is suppressed below normal; when it is weak, carbon-14 production is boosted above normal.
What the magnetic field does is to partially shield the earth from cosmic rays which produce carbon-14 high in the atmosphere.
The curve is roughly fitted to mean values determined about every 500 to 1,000 years...
It's a great argument except for one, little thing.
The water is coming out of the hose at a steady rate as our model assumed!
(Strahler, 1987, p.158) Lingenfelter actually attributed the discrepancy between the production and decay rates to possible variations in the earth's magnetic field, a conclusion which would have ruined Morris's argument.
Henry Morris chose not to mention that portion of the paper!