Module 1 : Atmospheric Composition and Principles of Contaminant Behavior

Lecture 3 : The Greenhouse Effect on Earth

 

Feedback Loop

Positive Feedback

– Mechanisms that make things worse…

– e.g., Increasing CO2 in the atmosphere leads to the release of more CO2

Negative Feedback

– Mechanisms that are self-correcting…

– e.g., Increasing CO2 in the atmosphere leads to higher rate of CO2 removal, such as our CO2 cycle.

Plate Tectonics

Plate tectonics plays an important role in the CO2 cycle in that it helps to carry the carbonate rocks into the mantle, which are then released again by volcanic activities.

– Earth's lithosphere is broken into pieces (the plates).

– These plates float on top of the mantle, interacting with each other to produce the geological features we see and feel today.

Where Did O2 Come From?

The most important source of O2 on Earth is

Life and Photosynthesis.

  • Photosynthesis converts CO2 to O2 , and incorporates carbon into amino acids, proteins, and other components of living organisms.
  • O2 will be depleted from the atmosphere very rapidly without a source.
  • O2 is a very reactive chemical that likes to be combined with other elements through oxidation. For example, CO2 , H2O, FeO (rust) Þ That's how we make fire!
  • O2 Absorbs UV, which also transform some of the O2 into O3, which absorbs even more UV

⇒ O2 not only supports life, it also protect life!

UV light can break the water molecules to release oxygen, but the contribution is small….