Comprehensive abatement of greenhouse gases involves reducing the emissions of all greenhouse gases. Comprehensive abatement strategies require indices to trade off between gases based on their relative contributions to climate change and associated impacts. This paper presents the results of an integrated approach to determining the relative role of different gases in the greenhouse abatement policy. Scientific and economic processes represented by realistic reduced form models are combined to determine greenhouse gas for methane, nitrous oxide and HCFC-22 using CO2 as the datum. The analysis suggests that greenhouse gas indices depend critically on the choice of discount rates, uncertainties in greenhouse gas lifetime, and the degree of non-linearity in climate damages. Costs of carbon abatement and uncertainties in climate models are less important.