Do Warmer Temperatures Cause Higher Carbon Dioxide Levels?

Some people, notably Al Gore, show the correlation between CO2 levels and the temperature of the atmosphere near the earth's surface, and argue that the CO2 we're putting into the atmosphere will cause that temperature to go up. Of course, there's the old axiom that correlation does not imply causation. It could also be that the increase in CO2 levels doesn't cause the warm up but instead is a consequence of the warm up. If so, the increasing CO2 levels occurring now would not a priori be expected to correlate with warmer temperatures.

Plants take CO2 out of the atmosphere with photosynthesis, but also put it back with respiration. If there are more plants could it be that the CO2 levels would be higher due to their respiration, or some other mechanism? For instance, what about animals and small non-photosynthetic organisms like bacteria? If the earth is warmer, won't there be more animals and bacteria breathing and putting CO2 into the atmosphere? Could mechanisms like this account for higher CO2 levels when the earth is warm? If so, the higher CO2 levels would be a consequence of warmer temperatures, not the cause of them.