This case study applied sociocultural theory to examine the climate change ideas communicated by one group of middle school students (N = 39) in a suburban community on the U.S. East Coast. We investigated the ways in which students' participation in the sociocultural activities of their varied communities appeared to inform their understandings of climate change prior to formal classroom science instruction on the topic. Data sources included an 18-item multiple choice Climate Science Knowledge Assessment Instrument (CSKAI), interviews investigating students' content knowledge and perspectives related to climate change, and drawings examining how students saw climate change in relation to their own lives. We interpreted learners' sociocultural activities as having implications for: (1) the kinds of scientifically-informed climate change ideas they brought to the classroom; (2) the sources of climate change information they perceived as trustworthy; and (3) the extent to which they viewed climate change as problematic, or as having potential connections to their lives. Findings also suggested that students' engagement with media within and beyond their school-based learning experiences -- even prior to formal instruction on climate change -- appeared to most strongly inform their ideas about climate change. We concluded that viewing students' climate change understandings as a product of the unique sociocultural activities in which they are already participating may provide a valuable foundation for planning science learning experiences that resonate personally with students.