The Durban Platform talks, aiming for a new global agreement in 2015, present an opportunity to assess and strengthen the international climate change effort. Since launching the U.N. Framework Convention on Climate Change two decades ago, governments have tried both “top down” and “bottom up” approaches. Neither has achieved the levels of participation or ambition needed to reverse the continued rise of global greenhouse gas emissions. Going forward, governments should draw on both models to forge a more effective global agreement.