Background/Question/Methods In order to educate decision makers and voters capable of making informed policy decisions in today’s rapidly changing global environment, K-12 teachers must fully understand the linkages among photosynthesis, respiration, and atmospheric CO2. Inquiry-based activities allow learners to build content knowledge and science process and critical thinking skills by connecting their previous knowledge with new ideas and evidence. We will present an intensive 5-day curriculum for an inquiry-based mini-course for K-12 teachers on the carbon cycle. Results/Conclusions The course consists of a series of inquiry activities and discussions we designed to allow teachers to link the processes of photosynthesis and respiration to atmospheric CO2 while gaining hands-on experience with affordable scientific equipment they can use in their classrooms, making and testing predictions about gas exchange processes, and working with data. The week starts with an engagement inquiry and discussion on how CO2 concentrations in the atmosphere affect temperature. This is followed by a series of activities on the processes and organismal level consequences of photosynthesis and respiration (e.g. what does a plant need to grow and breathing and holding your breath). The activities in the next part of the curriculum link these two processes with ecosystems and changes in atmospheric CO2 (e.g. the catastrophe of Biosphere 2, the carbon scavenger hunt, and how does carbon move through the environment). Our presentation will also include a discussion of our experiences teaching the curriculum to Philadelphia high school teachers and potential pitfalls to avoid in the future.