Climate treaties have progressed over time to pledge substantial reductions in global warming. This is surprising, given that theories of climate politics emphasize collective-action problems and domestic deadlock. I first describe the process of updating climate mitigation targets under the Paris Agreement. Then I develop a theoretical argument that explains target changes based on how countries are situated in economic and political networks. Trade flows create competitive economic pressures that may undermine climate action, but these pressures may ebb when partners also commit to act. I argue that political networks support conditional cooperation, especially when institutional design promotes gradual commitments. I use spatial regression models to study how countries’ climate targets are related to their partners’ prior targets. I find that countries pledged stronger updated mitigation targets in the Glasgow Climate Pact when their closest political partners submitted strong targets in the Paris Agreement. This suggests the Paris Agreement drove conditional cooperation on mitigation.