What term describes the imbalance in Earth's energy budget caused by greenhouse gases?

Radiative forcing describes the imbalance in Earth's energy budget caused by greenhouse gases. It measures how an external influence changes the net flow of radiation entering and leaving the climate system, usually in watts per square metre.

When carbon dioxide, methane, or other greenhouse gases increase, they absorb more of Earth's outgoing infrared radiation. Less energy escapes to space immediately, creating positive radiative forcing and a warming influence. The climate system then gradually warms until increased outgoing radiation helps restore balance.

The term is sometimes confused with Earth's energy imbalance. Energy imbalance is the measured net heat gain or loss, while radiative forcing refers to the cause or imposed change in the radiation budget. Greenhouse gases are positive forcings; reflective aerosols and increased surface albedo can produce negative forcing.

Radiative forcing is also used for changes in solar output, volcanic aerosols, land cover, and other climate drivers. Modern assessments often use effective radiative forcing, which includes rapid atmospheric adjustments while separating the initial driver from slower temperature feedbacks.