The overall goal of the research project is to investigate and produce knowledge about how teacher educators and student teachers are influenced when critical mathematics education (CME) is introduced in a thematic context of climate change, in their teaching and learning situation. The aim of CME is to teach mathematics through issues of social justice, inviting discussion in the mathematical classroom. Climate change can be seen as an instance of social justice, it does not affect everybody the same, some nations use more natural resources than others, etc. An empirical investigation is done at teacher education at Malmö university at a compulsory course in statistics. We study the situation both from a teacher and a student teachers’ perspective. Findings so far suggest that the complexity in the situation increases. We provide one explanation for this increase in complexity. Further we suggest ways of dealing with this complexity to support teachers and student-teachers in using CME in their teaching and learning.