To prepare students to make informed decisions and gain coherent understanding about global climate change, we tested and refined a middle school inquiry unit that featured interactive visualizations. Based on evidence from student pre-test responses, we increased emphasis on energy transfer and transformation. The first iteration improved comprehension of the visualizations resulting in better understanding of energy transfer (n = 67). The second iteration improved understanding of energy transformation (n = 109) by adding pivotal cases, reducing deceptive clarity, and emphasizing distinguishing of ideas. Focusing student investigations in the second version allowed students to make more normative, personally relevant decisions related to their energy use. These iterative refinements reflected knowledge integration principles and offer guidance for designers of inquiry units. (Contains 6 tables and 13 figures.)