The effects of boundary layer aerosol particles on the electric field measurement of the DC global circuit are considered. Aitken (condensation) nuclei concentrations are found to have systematic local seasonal variations which obscure the global behavior of the DC circuit. These local variations appear to be the result of several seasonal factors, including variations in atmospheric mixed layer heights, variations in the productions rates of anthropogenic aerosols, and variations in surface wind speed. Air-Earth conduction current measurements made by W. Cobb at Mauna Loa (1977–1983), a site remote from sources of pollution and mostly above the boundary layer, appear to be relatively free of aerosol particle effects. The Mauna Loa data are examined and the air-Earth current is found to peak in the northern hemisphere summer, consistent with the peak of the global thunderstorm activity in the same season. A reanalysis of the entire Carnegie and Maud ocean data set as well as ongoing Schumann resonance results support this finding. However, the general absence of a distinct semiannual signal remains unresolved.