Pop Quiz: Pre-Industrial Carbon
Answer: C) 280 parts per million
The concentration of atmospheric carbon dioxide--measured in parts per million (PPM)--has recently entered the mainstream as scientists debate the concentration above which we must not go if we are to avoid the worst consequences of global climate change. Before the onset of the Industrial Revolution, the concentration of atmospheric CO2 was around 280 parts per million. As of January 2007, the concentration was measured at 383 PPM, which is higher than it has been in the last 650,000 years.