  As one knows, strong discrepancies are found between the different precise
measurements of the gravitational constant carried out in Earth-based
laboratories. While the precision are increasing in different laboratories and
with various methods, these measurements are even more and more discordant. We
have shown since 2002 that an improved 5D Kaluza-Klein (KK) theory may provide
a satisfactory explanation to these discrepancies by referring to the
geomagnetic field as a possible cause. Here we take advantage of different
precise measurements performed at the same location but at different epoch to
address the temporal variation of the gravitational constant measurements.
