It seems that there is a substantial difference between the Earth's net negative charge (~ 500,000 C) and it's surface charge (`26,000 C).
http://www.nofc.forestry.ca/fire/faq_lightning_e.php#one "The Earth is electrically charged and acts as a spherical capacitor. The Earth has a net negative charge of about a million coulombs, while an equal and positive charge resides in the atmosphere." AND amongst others that are close. http://www.madsci.org/posts/archives/2000-10/972662284.Es.r.html "The solid Earth has a negative charge of about a half million coulombs. The atmosphere has a roughly equal and opposite charge, so that the Earth as a whole is roughly neutral. The charge difference produces a "fair weather electric field" in the lower atmosphere averaging about 6 volts per meter -- however, this field varies strongly with altitude, and is nearly 100 volts per meter at ground level. The total voltage difference between the ground charge and the atmosphere's charge (which exists roughly 30-50 km up) is about 300,000 volts. A simple calculation shows that the total energy stored in the fair weather electric field is 150 billion joules."
