This chapter looks at several interpretive models that help to define and explains the equity debates about responses to climate change. It discusses equity issues in climate discourses, distributional principles and allocational issues, procedural fairness, and the relationship of equity issues to social solidarity. A two-dimensional map of human values provides a tool for bringing equity issues into integrated assessment. The chapter deals with suggestions for ways to incorporate equity concerns into integrated assessment. The assumption that decision-makers are responsive to prices underlies the economic modules of all integrated assessment models. Efficiency, unlike equity, is inherent in the very idea of integrated assessment. Historical responsibility as an equity principle has strong support in the literature and politically in developing countries, but there are also valid counter-arguments. Issues of equity in climate change serve to highlight the central importance of the concept of social solidarity to understanding the social and political discourses about climate.