At international climate conferences, the European Union and its member states both are negotiating partners – does this make it an actor in international politics? The EU signs the treaties to protect the climate, the member states ratify and translate them into national policy. Based on the literature on actorness, Klaus Jacob and Julia Teebken identify in their articel different dimensions in which the EU’s actor quality is articulated. Actorness has internal dimensions, such as the transfer of responsibilities, and external dimensions, such as the recognition as a contracting party by other states. Actorness, however, cannot be grasped by analysing institutions alone, but also arises discursively and situationally. With regard to EU actorness four critical points in time in international climate policy were considered, which showed that actorness in the policy field has increased overall over time, but that the full potential has not yet been exploited. In some dimensions, a temporary decline in actorness could be observed, especially at the Copenhagen summit.