In many climate change mitigation cost-effectiveness studies that do n
ot develop endogenous shadow prices for the value of carbon it is nece
ssary to determine the time value of reductions in carbon dioxide emis
sions. This paper examines the implications for the time value of carb
on of exogenously specifying (2) the path of marginal damages over tim
e, (2) the path of emissions over time, and (3) that the emissions pat
h follow an optimal trajectory over time.