The latest data, as of March 2006, shows CO2 levels now stand at 381 parts per million (ppm)---100ppm above the pre-industrial average.
Despite its small concentration, CO2 is a very important component of Earth's atmosphere, because it absorbs infrared radiation at wavelengths of 4.26 µm and 14.99 µm and enhances the greenhouse effect.
The initial carbon dioxide in the atmosphere of the young Earth was produced by volcanic activity; this was essential for a warm and stable climate conducive to life. Volcanic activity now releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year. Volcanic releases are about 1% of the amount which is released by human activities.
Since the start of the Industrial Revolution, the atmospheric CO2 concentration has increased by approximately 110 µL/L or about 40%, most of it released since 1945. Monthly measurements taken at Mauna Loa since 1958 show an increase from 316 µL/L in that year to 376 µL/L in 2003, an overall increase of 60 µL/L during the 44-year history of the measurements. Burning fossil fuels such as coal and petroleum is the leading cause of increased man-made CO2; deforestation is the second major cause.
Scott, the source you were quoting was simply wrong.
Volcanoes also eject the kind of compounds that environmentalists call greenhouse gases. A single eruption the size of the Mt. St. Helens eruption released more of these gases, dust and ash into the atmosphere than all such emissions by human activity since the beginning of recorded human history. And there are numerous volcanic eruptions yearly.
Here, he's comparing apples and oranges. Greenhouse gases vs. volcanic ash. Most of what volcanoes spew out is simply ash that falls to the ground over the next few months. And he doesn't cite any of his sources.