This paper analyzes insufficiencies in UN negotiations and identifies a set of characteristics that would make a complementary institutional design efficient. A coalition among nations with high climate ambitions is suggested. Such a coalition should introduce measures that leaders can control and be accountable for—measures that are short-term and fewdimensional, and that incentivize efficient reductions, prevent leakages to outside nations, and sanction non-compliance. A coalition should also provide incentives to outside emitters and encourage new members. A Climate Coalition that harmonizes minimum national carbon prices (i.e. carbon taxes), introduces a common carbon tariff, and welcomes new members would meet the criteria and have the potential to emerge at a global level.