Since the 2015 Paris Agreement, the approach on international climate equity has been bottom-up, with the production of voluntary contributions by Parties. The construction of a judgement on these contributions' fairness needs to result in a trade-off between legitimacy - acknowledging as many existing visions of climate equity as possible - and conclusiveness. In this exploratory study, we use survey techniques in the original perspective of empirical social choice: we observe individual judgements and values from citizens to provide insights on building a legitimate collective judgement. Both in France and in the United States, we elicit people’s adhesion to general equity principles, and judgements on illustrative theoretical cases as well as some countries’ existing contributions. We then discuss the robustness and legitimacy of our results.