Following the success of the High Ambition Coalition (HAC) in contributing to the UNFCCC Paris Agreement in 2015, the European Union (EU), which played an instrumental role in the coalition, remobilised, along with its partners, the HAC to support two key international climate agreements in 2016: the Kigali Amendment to the Montreal Protocol and the ICAO Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). Despite these negotiations taking place simultaneously within a push for climate action following COP21 and having significant EU involvement, the HAC produced mixed results. While the HAC appeared successful in helping to secure an ambitious agreement in Kigali, thanks to broad involvement from the EU and HAC partners, this was not the case with ICAO CORSIA, where the EU struggled to mobilise its HAC partners. This article answers the question Why was the EU successful in its involvement with the High Ambition Coalition in the negotiations leading to the Kigali Amendment yet unsuccessful in the ICAO CORSIA negotiations? In conducting a detailed “most similar” case study comparison, it identifies three contextual (scope) conditions that needed to be present for such success: capacity of the HAC for collective action, a favourable institutional environment in the negotiating forum in question, and the availability of sufficient time to influence the negotiations.

继高雄心联盟 (HAC) 于 2015 年成功为《联合国气候变化框架公约》巴黎协定作出贡献之后，在该联盟中发挥重要作用的欧盟 (EU) 重新动员了 HAC 及其合作伙伴，以支持两个关键目标： 2016 年国际气候协议：蒙特利尔议定书基加利修正案和国际民航组织国际航空碳抵消和减排计划 (CORSIA)。尽管这些谈判是在 COP21 后推动气候行动的同时进行的，并且欧盟也大力参与，但 HAC 的结果好坏参半。尽管由于欧盟和 HAC 合作伙伴的广泛参与，HAC 似乎成功地帮助在基加利达成了一项雄心勃勃的协议，但国际民航组织 CORSIA 的情况并非如此，欧盟在动员其 HAC 合作伙伴方面遇到了困难。本文回答了以下问题：为什么欧盟成功地参与了雄心联盟的基加利修正案谈判，但在国际民航组织 CORSIA 谈判中却失败了？在进行详细的“最相似”案例研究比较时，它确定了取得成功所需的三个背景（范围）条件：HAC 采取集体行动的能力、相关谈判论坛中有利的制度环境以及有足够的时间来影响谈判。