There is a ridiculous amount of information on the internet for this unit. I ultimately ended up creating my own materials for this but reviewed a lot of it through various sources.
Links
https://en.wikipedia.org/wiki/Feedback#Positive_and_negative_feedback
https://en.wikipedia.org/wiki/Carbon_cycle
http://www.esrl.noaa.gov/gmd/ccgg/index.html
Next Up: Growth in Student Learning