Carbon emissions refer to the release of greenhouse gases and/or their precursors into the atmosphere over a specified area and period of time. Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities, and it makes up the vast majority of greenhouse gas emissions. CO2 is a colorless, odorless, and non-poisonous gas formed by combustion of carbon and in the respiration of living organisms. Carbon dioxide emissions are those stemming from the burning of fossil fuels and the manufacture of cement, and they include carbon dioxide produced during consumption of solid, liquid, and gas fuels as well as gas flaring.

Other greenhouse gases that contribute to carbon emissions include methane (CH4) and nitrous oxide (N2O) . Methane is emitted from sources such as natural gas and petroleum products, organic waste sent to landfills, and wastewater treatment plants. Nitrous oxide is also emitted from wastewater treatment plants and from land use and management activities.

Carbon emissions have a significant impact on the Earths climate, as carbon dioxide is an important heat-trapping gas that contributes to global warming. Human activities are altering the carbon cycle by adding more CO2 to the atmosphere and by influencing the ability of natural sinks, like forests and soils, to remove and store CO2 from the atmosphere. Reducing carbon emissions is crucial to mitigating the effects of climate change, and this can be achieved by producing more energy from renewable sources and using fuels with lower carbon contents. Carbon capture and sequestration (CCS) is another technology that can potentially greatly reduce CO2 emissions from new and existing coal- and gas-fired power plants, industrial facilities, and other stationary sources.