Human Energy Systems is one of six units in the Carbon: Transformations in Matter and Energy (Carbon TIME) curriculum, which was developed through an NSF-funded research collaboration focused on learning progressions to support environmental literacy. These units were developed for middle and high school students. The units (http://carbontime.bscs.org/units) are designed in three groups; each group increases in scale from the previous one. Students should first complete the foundational unit, Systems & Scale, and then at least one of the three units at the organism level. They may then complete the Ecosystems unit before moving into the culminating Human Energy Systems unit. Each large-scale unit focuses on three questions: (1) Where are the carbon pools in the environment? (2) How are carbon atoms cycling among pools? and (3) What is happening to energy? In the Human Energy Systems unit, students investigate a series of phenomena focused on global carbon cycling and climate change. The highly guided sequence of six lessons helps students interpret large-scale datasets, trace global movements of matter and energy, and explain the consequences of human choices for changes in atmospheric CO2. Extensive supporting information is provided within each lesson and on the resources page (http://carbontime.bscs.org/resources). The assessment site (http://ibis.colostate.edu/MSP/CTIME/Index.php) includes pre/posttests for each unit and for the overall curriculum. The overview provided here (http://media.bscs.org/carbontime/files/unit_synopses.pdf) provides a helpful orientation to this complex resource.