Abstract No other environmental issue today has as much potential to alter life on Earth as does global climate change. Scientific evidence continues to grow; indicating that climate change is occurring now, and that change is a result of human activities (National Research Council [NRC], 2010). The need for climate literacy in society has become increasingly urgent. Unfortunately, understanding the concepts necessary for climate literacy remains a challenge for most individuals. A growing research base has identified a number of common misconceptions people have about climate literacy concepts (Leiserowitz, Smith, & Marlon 2011; Shepardson, Niyogi, Choi, & Charusombat, 2009). However, few have explored this understanding in high school students. This sequential mixed methods study explored the changing conceptions of global climate change in 90 sophomore biology students through the course of their participation in an eight-week inquiry-based global climate change unit. The study also explored changes in students' attitudes over the course of the study unit, contemplating possible relationships between students' conceptual understanding of and attitudes toward global climate change. Phase I of the mixed methods study included quantitative analysis of pre-post content knowledge and attitude assessment data. Content knowledge gains were statistically significant and over 25% of students in the study shifted from an expressed belief of denial or uncertainty about global warming to one of belief in it. Phase II used an inductive approach to explore student attitudes and conceptions. Conceptually, very few students grew to a scientifically accurate understanding of the greenhouse effect or the relationship between global warming and climate change. However, they generally made progress in their conceptual understanding by adding more specific detail to explain their understanding. Phase III employed a case study approach with eight purposefully selected student cases, identifying five common conceptual and five common attitudebased themes. Findings suggest similar misconceptions revealed in prior research also occurred in this study group. Some examples include; connecting global warming to the hole in the ozone layer, and falsely linking unrelated environmental issues like littering to climate change. Data about students' conceptual understanding of energy may also have implications for education research curriculum development. Similar to Driver & While no statistical relationship between students' attitudes about global climate change and overall conceptual understanding emerged, some data suggested that climate change skeptics may perceive the concept of evidence differently than non-skeptics. One-way ANOVA data comparing skeptics with other students on evidence-based assessment items was significant. This study offers insights to teachers of potential barriers students face when trying to conceptualize global climate change concepts. More importantly it reinforces the idea that students generally find value in learning about global climate change in the classroom.