Carbon dioxide levels prior to the start of the industrial revolution were approximately 280 parts per million by volume, or ppmv. Current levels of carbon dioxide are more than 380ppmv, and have been steadily increasing at a rate of 1.9ppmv per year since the year 2000. To put these numbers into focus, the natural range of CO2 over the last 650,000 years has been between 180 and 300 ppmv. According to a special report issued by the IPCC, we will see CO2 concentrations in the range of 490 to 1260 ppmv by the end of the 21st century 7. According to the EPA, the total amount of U.S. greenhouse gas emissions in 2007 was 7,510 teragrams, or 8.3 billion short tons, of carbon dioxide equivalents 8. Overall, from 1990 to 2007, total emissions of CO2 increased by 20.2 percent, or 1.1 billion short tons 9.