Methane
Methane (CH4) is a colorless gas and a potent Greenhouse gas emitted by both natural processes and human activities. Although it remains in the atmosphere for less time than carbon dioxide, each unit of methane traps substantially more heat over common assessment periods.
In simple terms
Human-caused methane comes mainly from energy systems, livestock and manure, rice cultivation, landfills, and wastewater. Wetlands and other natural processes also emit it, while chemical reactions and soils remove it from the atmosphere. As a Greenhouse gas, methane is included in emissions inventories. Its climate effect can be expressed as Carbon dioxide equivalent using a Global warming potential for a stated time horizon and assessment source. Because the gas is comparatively short-lived, sustained reductions can slow near-term warming, but they do not substitute for reducing long-lived carbon dioxide emissions.
Why it matters
Methane is responsible for an important share of human-caused warming and often has identifiable emission points. Detecting leaks, changing waste and livestock practices, and capturing usable gas can therefore deliver relatively rapid climate benefits. Accurate Carbon accounting still requires appropriate activity data, an Emission factor or direct measurement, clear boundaries, and consistent treatment of uncertainty.
Example
A landfill operator measures captured gas and estimates uncaptured methane using documented waste data and an Emission factor. It reports the result in tonnes of methane and converts it to Carbon dioxide equivalent with a named Global warming potential. It also explains measurement uncertainty rather than presenting the estimate as an exact reading.