In a post on the co-rotation of Earth and its magnetic field (Does the geomagnetic field rotate?), John Rennie raised the point that, if Earth's magnetic field were rotating about its dipole axis, it would generate an electric current in salt water and any other conductor on Earth. While the magnetic field does not rotate separately (as it co-rotates with Earth), its dipole axis is constantly wandering relative to Earth's spin axis, currently at a rate of about 6.3 meters/hour. Could this introduce an electric current in the global saltwater ocean and so inject thermal energy? If it does, can that effect be quantified? Interestingly, the rate of dipole axis wander increased in the 1990s from 1.7 meters/hour to about the current rate - a potential thermal effect of dipole axis wander, if in any way signficant, might thus contribute to ocean warming since the 1990s.