While researchers have stressed the importance of engaging students in activities that enhance their reasoning practices, few have scrutinised the factors that impact the reasoning involved in such activities. We explored the role of attitudes in student-group interactions concerning a climate change-related socio-scientific issue and how those attitudes emerged from the reasoning process. We applied Martin and White's [(2005). "The language of evaluation: Appraisal in English." Palgrave Macmillan] appraisal framework for studying attitudes in oral language to analyse two student groups involved in a discourse as they constructed arguments supporting further petroleum exploration. The two groups displayed unique patterns of attitudes towards additional exploration: one group displayed strong, positive attitudes, while the other displayed varied attitudes, including doubt and insecurity. These more complex attitudes in the second group were important to how these students reasoned about the issue, enabling them to appreciate the complexity of the issue, as the expression of multiple perspectives and doubt opened a richer inquiry into the socio-scientific issue, enhancing the quality of their reasoning. Our findings point to the significance of considering students' attitudes when organising activities were students' reason about a socio-scientific issue.