An ongoing study in Yellowstone National Park seeks to measure the emissions of carbon dioxide (CO2) as a response to geologic activity and as a possible predictor of some geologic events. A story covering this study notes that researchers estimate that Yellowstone emits 45,000 tons of CO2 per day. That is about 16.5 million tons per year.
The EPA estimates that the average car emits between five and six tons of CO2 per year. So natural geologic activity in Yellowstone contributes CO2 equivalent to about 3 million cars. The current attempts by the EPA to limit CO2 emissions would be dangerous for the American economy, but they would have no impact on the millions of tons Yellowstone emits every year.
More seriously, the EPA regulations would also have little impact on the billions of additional tons of CO2 that China, India, and the developing world will emit each year in the decades ahead. As a result, the regulations would have damaging impacts on the American economy, but just like cap-and-trade restrictions, they would have negligible impact on world temperatures.