This thesis aims to compare and analyze how the Swedish political debate on climate action policy between the two parties the Centre Party and the Green Party has played out from 2006 to 2020. This is done using two sub-theories within the grander theory of institutionalism. In addition to this, Katarina Barrling's research on the internal party cultures and collective selfimages within Swedish political parties will be used and referred to in the analysis of this study to better explain the development of this policy debate between the Centre Party and the Green Party from our choice of theories and subsequent research questions. This study uses a qualitative approach to conduct a longitudinal study in order to explain the development of the debate on climate action policy between these two parties. By looking at and analysing debate articles from six major national news outlets in Sweden, the rhetorical language and values promoted by the Centre Party and the Green Party in this debate on climate policy can be established and compared. In terms of results, the study shows that the climate policy debate between the Centre Party and the Green Party has to a large extent remained the same with a consistently heated and adversarial rhetoric used by the two parties against each other throughout the years. The study also shows that several important normative/institutional values similar to those found in Katarina Barrling's research on the Centre Party and the Green Party are visible in the arguments displayed by these two parties in this debate on climate action policy. Like Barrling's research indicates, the Centre Party clearly displays institutional values or traits such as "pragmatism" and having a "practical mindset" in their rhetoric in this debate, and the Green Party clearly displays institutional values or traits such as thinking "creatively" and "radically" about climate policy ideas and wanting to influence policy decisions as much as possible. Nevertheless, despite these important findings, some of Barrling's empirical claims about the norms and values embedded within each of these two parties were not detected or proven through this thesis. These undetected claims concerned the image of the Centre Party as being a "cooperative" party in nature, and the Green Party as being a highly "individualistic" party in nature with a lack of internal unity among its members.