Isn carbon dioxide produced naturally? Why are humans to blame?
Carbon dioxide is a by-product of many natural processes on Earth. However, these processes cannot explain the rise in carbon dioxide levels that we have measured over the past several decades. For example, natural decay of plant matter releases CO2 into the atmosphere, but averaged over a year this is almost exactly cancelled by removal of CO2 by plants as they photosynthesize and grow. In fact, estimates of deforestation and oil, coal, and natural gas consumption allow the yearly release of CO2 by humans to be calculated. The actual atmospheric CO2 abundance is currently rising at only half this rate. Therefore, not only is the current CO2 increase caused by humans, but much of the CO2 released by humans is going somwhere other than the atmosphere. See here for a more detailed summary.
