In the context of the global response to the threat of climate change, the question arises of how to fairly share the overall global effort required to mitigate climate change based on fundamental ethical principles. The Climate Equity Reference Project (CERP) framework (which evolved from earlier Greenhouse Development Rights work) is an approach that allows users to explore various ways of defining and expressing fair shares, and calculate the results for any country. It takes nations’ historical responsibility for greenhouse gas emissions and their financial capacity to reduce emissions and otherwise address climate change as the basis for assigning fair shares of the overall global effort, doing so in a way that considers the disparities in emissions and income not just among countries, but also among individuals within countries.

The Climate Equity Reference Calculator and its web interface, cerc-web, allows users to calculate fair share contributions for each country, based on a user’s selection of equity-related parameters. The cerc-web interface serves as a user interface to, and enhances the capabilities of, the calculator “engine” backend. Taken together, the “engine” and cerc-web represent the only official implementation of the theoretical GDRs and CERP frameworks by their authors.