What was done
In an invited review of the pertinent scientific literature, the authors evaluate what was known near the close of 2004 about the effects of atmospheric CO2 enrichment on plant respiration from the cellular level to the level of entire ecosystems.

What was learned
Gonzalez-Meler et al. report that "contrary to what was previously thought, specific respiration rates are generally not reduced when plants are grown at elevated CO2."  Nevertheless, they note that "whole ecosystem studies show that canopy respiration does not increase proportionally to increases in biomass in response to elevated CO2," but they also find that "a larger proportion of respiration takes place in the root system [when plants are grown in CO2-enriched air]," which once again complicates the issue.

What it means
The authors ultimately conclude that "fundamental information is still lacking on how respiration and the processes supported by it are physiologically controlled, thereby preventing sound interpretations of what seem to be species-specific responses of respiration to elevated CO2."  Hence, they refreshingly state that "the role of plant respiration in augmenting the sink capacity of terrestrial ecosystems is still uncertain," setting an example of wise restraint that many climate alarmists and politicians would do well to follow with respect to the question of CO2 effects on world temperatures.