Fixing global carbon emissions: choosing the best target year

Confronted with issues fraught with enormous complexity, policy makers have shown a proclivity towards considering and enacting simple and apparently equitable structures that can be easily explained to and understood by their constituents. In the global change arena, this tendency seems to lead to consideration of global emissions targets defined by levels achieved in some specific year along a previously unregulated trajectory. The question raised then is one of determining which year's emissions would, if set as a global limit, maximize the discounted net benefit of the policy? In addition, how sensitive is that year to changes in the damages associated with a doubling of atmospheric concentrations of greenhouse gases and/or the pace of near-term, unregulated emissions of those gases? Results produced here support two qualitative results that answers these questions. (author)