Climate Bathtub Model of Earth's Carbon Cycle

Climate Bathtub Model of Earth's Carbon Cycle

The "Climate Bathtub" model is a conceptual model of a portion of Earth's carbon cycle. It is especially useful for helping people understand how anthropogenic (human-caused) emissions of carbon dioxide, primarily from fossil fuel burning, influence the amount of carbon dioxide in our planet's atmosphere. The "Climate Bathtub" model was initially articulated by John D. Sterman and Linda Booth Sweeney.

We developed a series of animations to illustrate a range of situations which can be portrayed by the "Climate Bathtub" model. The first (below) depicts Earth's climate in an equilibrium state, in which the amount of carbon flowing into the atmosphere is equal to the amount being removed from the atmosphere.

{C}{C} {C} {C}

In the equilibrium state, the amount of carbon dioxide in the atmosphere remains steady (doesn't change over time). In this version of the "Climate Bathtub" model:

  • the bathtub represents Earth's atmosphere
  • the water in the tub represents the amount of carbon dioxide in the atmosphere
  • the water flowing into the tub from the faucet represents carbon dioxide being added to the atmosphere (via processes such as respiration and decay of plants, dissolution from ocean water, etc.)
  • the water flowing out of the tub via the drain represents carbon dioxide being removed from the atmosphere (via processes such as photosynthesis, being dissolved into the oceans, etc.)

During much (but not all!) of the "natural" (pre-human) history of Earth, the atmospheric portion of the carbon cycle was in a more-or-less equilibrium state as is shown in this animated version of the "Climate Bathtub" model.