Final answer:
The equilibrium in the Earth's Energy Budget is the balance between incoming solar energy and outgoing infrared radiation, maintaining Earth's average surface temperature.
Step-by-step explanation:
An equilibrium in terms of the Earth's Energy Budget refers to the balance between the energy Earth receives from the Sun and the energy it radiates back into space. Earth reaches a state of dynamical equilibrium where the power input from the Sun is equal to the power output, averaged over the surface to be about 240 W/m². This state of balance ensures that Earth maintains an average surface temperature that is conducive to life. The energy from the Sun, at a rate of 1,360 W/m², is immense compared to human energy consumption but only a portion is absorbed due to the geometric considerations that the Earth's projected area is much smaller than the total surface that radiates energy. During the pre-industrial equilibrium, the temperature balance was achieved without additional radiative forcing from increased CO₂ levels. Any gain in temperature would lead to an increase in the Earth's radiation output until it matches the increase in absorbed solar energy. Understanding this delicate balance is crucial for grasping the impacts of greenhouse gases on global temperatures and climate change.