Climate governance beyond the United Nations Framework Convention on Climate Change (UNFCCC)—including countries, companies, civil society, and international organizations, forming cooperative initiatives—is increasingly framed as complementing, supporting, and even substituting the multilateral negotiations. Cooperative initiatives activating nonstate actors could help bridging the ‘ambition gap’ between governmental greenhouse gas mitigation pledges and the decarbonization pathway needed to halt global warming at 2°C. But what do we know about the performance of cooperative initiatives and their participants? We examine the content of five databases aiming to capture the emerging field of cooperative initiatives and assess whether it is possible to measure the performance of cooperative initiatives based on current data. Overall, we find a substantial lack of ex post data for measuring performance. Available studies either focus on nonemission-related qualitative variables and characteristics of cooperative initiatives such as governance function, participants composition, and thematic areas, or use quantitative modeling approaches to estimate their potential impact. Consequently, we currently lack information to assess how existing initiatives perform in relation to the socio-technical systems they are intended to intervene in, or how initiatives align, scale-up, and form low-carbon pathways. Given the increasingly important role and legitimacy attributed to cooperative initiatives in addressing climate change, we argue that focusing more on gathering ex post data, improving exchange between academic and policy-oriented work, and developing assessment methods accommodating diversity in terms of function, goal, and output, are needed to understand the performance of climate governance beyond the UNFCCC. WIREs Clim Change 2016, 7:486–500. doi: 10.1002/wcc.396. For further resources related to this article, please visit the WIREs website.