Encyclopedia of Earth
Encyclopedia of Earth: Greenhouse Gas
Explains what greenhouse gas is, how the greenhouse effect works, and the history of fossil fuel combustion. Causes of other damaging greenhouse gases, including methane, nitrous oxide, chlorofluoracarbons, hydrofluorocarbons, and...
University of Illinois
University of Illinois: Illinois State Water Survey: Nitrogen Cycle: Human Impact on the Nitrogen Cycle
An overview of the impact of human activities on the environment and how those actions effect the nitrogen cycle.