Interest has developed in knowing the net greenhouse gas (GHG) emission or carbon footprint of food production systems and to mitigate those emissions toward the goal of no effect on global warming. Quantifying and evaluating production system emissions requires a modeling approach. Models at various levels of detail are used to estimate GHG emissions from sources on dairy farms. Integration of these models considers the interactive effects among farm components to determine whole farm emissions. Life cycle assessment is often included to incorporate all sources from the production of resources used on the farm to emissions from farmland, animals, manure handling, and combustion or decomposition of fossil carbon. An important use of dairy farm models is quantifying and comparing life cycle carbon footprints to determine best management practices. Mitigation strategies are evaluated alone and in combination to refine production systems toward the goal of net zero milk production.