Generally used as shorthand for ‘carbon emissions’. Greenhouse gases, including carbon dioxide (CO2) and methane, contain carbon and contribute to global warming. The temperature of the Earth depends on a balance between incoming energy from the Sun and the energy that bounces back into space. Carbon dioxide particles in the air absorb heat that would otherwise be lost to space. Some of this energy is re-emitted back to Earth, causing additional heating of the planet. Many organisations are trying to reduce their carbon footprint in order to reduce emissions of greenhouse gases, of which carbon dioxide is the main gas. See also Carbon Footprint and Greenhouse Gases. .