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Human Energy Systems | Instructional Models

Instructional Models

Observations, Patterns, and Models

Like all Carbon TIME units, this unit consists of an instructional model designed to teach for a mastery of the unit’s inquiry and application goals. For more information about this, see the “Carbon TIME Instructional Model” document at The instructional model for the Human Energy Systems includes two complete cycles where students act as questioners, investigators and explainers. Phase 1 focuses on data and modeling associated with global climate change; Phase 2 focuses on global carbon cycling and how it is affected by human actions and technologies.

Instructional Model

Observations, Patterns, and Models in the Human Energy Systems Unit

Each phase has its own set of connected observations, patterns, and models.

Observations, Patterns, and Models for Phase 1: Climate Change Observations and patterns: trends in global climate data. Students investigate multiple representations of data about four global phenomena, comparing the representations to look for patterns in the data. They end the Lesson 2 with four clear long-term trends:

  • The extent of Arctic sea ice is decreasing
  • Sea levels are rising
  • Global average temperatures are rising
  • Global concentrations of CO2 are rising

Observations, Patterns, and Models in the Human Energy Systems Unit

Models: the Greenhouse Effect and CO2 as the driver. Students learn to use the Greenhouse effect to explain the connections among the long-term trends: Increasing CO2 levels are causing increases in global temperatures; the increasing temperatures are causing sea level to rise and ice to melt. Thus atmospheric CO2 is the driver—the factor that causes change in the other variables.

Observations, Patterns, and Models in the Human Energy Systems Unit

Observations, Patterns, and Models for Phase 2: Global Carbon Cycling

Observations and patterns: Students use visualizations and graphs to investigate changes in atmospheric CO2 concentrations. Key patterns include:

  • The annual cycle: CO2 concentrations in the northern hemisphere decline every summer and rise every winter.
  • The long-term trend: Global CO2 concentrations have increased from about 310 to 400 ppm since the late 1950s.

Models (and Explanations): Students explain carbon cycling and energy flow between carbon pools by connecting global, macroscopic, and atomic-molecular scales, and answering the Four Questions:

  • Carbon Pools: carbon atoms are found in CO2, living organisms, soil organic carbon, oceans, and fossil fuels
  • Carbon Fluxes: Changes in photosynthesis drive the annual cycle; combustion of fossil fuels drives the long-term trend.
  • Energy Flow: CO2 and other greenhouse gases cause climate change.
  • Stability and Change: The photosynthesis and cellular respiration fluxes are large, but balanced. So the smaller but unbalanced flux from combustion of fossil fuels is steadily increasing the size of the atmospheric CO2

Observations, Patterns, and Models in the Human Energy Systems Unit