A reformulation of global warming potentials is propounded, that combines the time-horizon and discounting definitions, and covers both ordinary atmospheric forcing (via greenhouse gases) and its rate-of-change. Insofar as GWPs are used to guide investment and socioeconomic choices, there is merit in adopting cost-benefit techniques. The parametric equivalence of the two definitions applies for the ordinary atmospheric forcing; but for its rat-of-change, only the discounting definition gives realistic results, as shown in application to methane, a short-lived greenhouse gas.