The Carbon Cycle and Intro to Feedback Loops
This introductory reading is designed to provide you with some background information
about the carbon cycle, permafrost, and the Arctic tundra that we will use to build systems
diagrams. The reading also introduces modeling terminology (bolded terms defined in the
glossary).
Introductory video
Watch the seven-minute video report, “Thawing Permafrost—Changing Planet”
(https://www.youtube.com/watch?v=yN4OdKPy9rM or
https://science360.gov/obj/video/d8fe889b-8741-4a25-a68d-9541f1562b9b/thawing-
permafrost) for an introduction to the potential impacts of melting permafrost.
Photosynthesis and stored carbon
Plants and other photosynthetic organisms use energy from the sun to build high-
energy carbon compounds from carbon dioxide that they take up from the atmosphere.
Normally, these high-energy carbon compounds are only a temporary storage form of the
carbon and energy they contain. Plants, animals, and decomposers will “burn” the organic
carbon compounds in a process called respiration, using the energy and releasing the
carbon dioxide back into the atmosphere. This flux, or movement of carbon between the
atmosphere and biosphere, is an important part of the global carbon cycle. Fossil fuels—
including coal, natural gas, and crude oil—contain carbon compounds that came from
plants living hundreds of millions of years ago. The formation of large organic carbon
reservoirs like those that produced fossil fuels removed some of the carbon from the
