Unlike the vast preponderance of planets, earth has been bequeathed a hospitable environment in which to thrive. Up to now, man's activities have affected this environment negligibly. Scientists are becoming convinced, however, that release of carbon dioxide (CO2) from combustion of fossil fuels will lead to a significant modification of the global climate (see Woodwell). How should we think about such a destruction of our heritage? Should it be treated as anathema, like bondage? Or should the pace and extent of use of our global commons be subject to the same reasoned balancing of costs and benefits as other economic activities? The present paper takes the second approach -- asking how fast the global economy should allow a buildup of atmospheric CO2. The first section reviews the current scientific knowledge on this subject, while the second puts this into an optimal growth framework. The third section then presents a numerical example, while the last presents some realistic policy views on the subject.
