In order to help address climate finance-related information needs under the UNFCCC, this paper explores the extent to which currently-available secondary data make it possible to estimate private finance mobilised by developed countries for climate action in developing countries. This is done by testing the implementation of two approaches: the first one based on an analysis of an investment-related commercial database, and the second one based on the use of publicly-available private finance leverage ratios. Due to data constraints, the focus is on renewable energy as a sub-set of climate mitigation activities. Volumes of private finance estimated as mobilised under the first approach are very partial, due to limitations of the database used, while the second approach results in highly inaccurate extrapolations due to a current lack of empirically-robust publicly-available private finance leverage ratios. These findings highlight the need for improved primary data collection, in particular by public climate finance providers on private co-finance, building upon the recent progress already achieved by a number of bilateral and multilateral development finance institutions. Further, very careful and transparent use should be made of leverage ratios, as they are highly sensitive to both the underlying calculation methods (e.g. in terms of attribution of mobilised private finance among public actors involved), as well as to core characteristics of public finance that result from varying mandates of development agencies and institutions. In any case, amounts of private finance mobilised by public actors and interventions (and ratios that can be calculated on such basis) should not necessarily be interpreted as reflecting their respective abilities to achieve effective and transformational climate action, which requires monitoring of impacts over time.