The number of studies seeking to empirically characterize the reduced-form relationship between a country economic growth and the quantity of pollutants produced in the process has recently increased significantly. In several cases researchers have found evidence pointing to an inverted-U “environmental Kuznets” curve. In the case of a major greenhouse gas, CO2, however, the evidence is at best mixed. This paper attempts to shed further light on this issue by using a newly developed dataset on emissions and by employing a new highly flexible functional form.