Taking your comment seriously: People have done the math on the heat directly released by burning fossil fuels, and it isn't that high. What CO2 does is keep

Taking your comment seriously: People have done the math on the heat directly released by burning fossil fuels, and it isn't that high. What CO2 does is keep more of the SUN'S heat on Earth. And that turns out to be a much more important contribution to the temperature of the Earth than the heat directly released by burning fossil fuels. Current CO2 levels are a full 50% higher than they were 80 years ago or so, and that makes a big, big difference.