Global Warming Potentials (GWPs) are used to estimate, compare and aggregate the relative climate effects of various greenhouse gases (GHGs). They are a measure of the relative radiative effect of a given substance compared to another, integrated over a chosen time horizon. This note provides basic information on GWPs and their use under the Convention and the Kyoto Protocol, in particular their use in guidelines for reporting GHG inventories and for preparation of national communications by Parties.