This paper examines the effects of political pressure groups (lobbies) on the size and stability of international climate agreements. We consider two types of lobbies, industry and environmentalists. We show the potential effects of lobbying using the STAbility of COalitions (STACO) model. We find that although lobby contributions may help to stimulate international cooperation, the resulting stable agreement does little to tackle climate change. Finally, we observe that, contrary to intuition, a member of a stable agreement can collect industry contributions.