Sources & Sinks

A source is any natural or human-induced process or activity that releases a greenhouse gas (GHG) or aerosol into the atmosphere. Alternatively, a sink is any process, activity, or mechanism that removes a GHG, an aerosol, or a precursor of a GHG or aerosol (e.g., volatile organic compounds, nitrogen oxides) from the atmosphere. Primary examples of sources and sinks for each major GHG (carbon dioxide, methane, and nitrous oxide) include:

Carbon dioxide (CO2)

  • Sources (natural): Microbial decomposition of organic material in the presence of oxygen, forest fires, and volcanoes.
  • Sources (human-induced): Burning of fossil fuels, deforestation, and the burning of solid waste.
  • Sinks: Photosynthetic vegetation, reforestation, and soils.

Methane (CH4)

Nitrous oxide (N2O)

The sidebar sections go into the detail of agricultural sources and sinks of GHG emissions and recommended mitigation strategies and case studies.