Future harm and current obligations: the case of global warming

There is a time during which aggregate benefits from greenhouse gas emissions dominate costs, but less comfort should be drawn from this situation than current emphasis on double CO2 scenarios suggests. The intertemporal asymmetry of impacts means initial benefits to most regions, from slight global warming, turn into very large economic costs, as warming continues. Economic decisions over what action, if any, to take concerning the greenhouse effect are essentially controlled by the social discount rate. The discount rate chosen implicitly attributes intertemporal weights to welfare and implies a moral stance. Once the future is considered from an ethical perspective a conflict is apparent between the view that the current generation need be unconcerned over the loss or injury caused to future generations, because they will benefit from advances in technology, investments in both man-made and natural capital, and direct bequests, and the requirement to avoid harming the innocent. Changes in units of welfare cannot be viewed as equivalent regardless of their direction. In general, doing harm is not cancelled out by doing good. The result is a rejection of the potential compensation principle and acceptance of the need to carefully consider the moral constraints upon economic activities creating global warming.