Let’s begin by developing our “common sense” of thermal science.

Let’s remember the general principle of heating (file « Présentation du chauffage à eau chaude » - Presentation of the hot water heating system).

We can compare a heated building to a reservoir:

• The level of water in the reservoir remains constant if there is as much water coming in as there is coming out
• The temperature level of the house remains constant if there is as much heat coming in as there is coming out (this can also be stated as “ the temperature level of the house remains constant if there is as much heat coming out as there is coming in”)

As such, the temperature of the Earth remains constant as long as it emits as much heat as it receives from outside (from the sun) or from inside (from the center of the Earth or from human activity).

Prior to the current Global Warming period, the situation of the planet could be represented by the following scheme:

Power received by the planet	Power emitted by the planet
Sun: 342 [W/m²] Geothermal energy: 0.05 [W/m²] ------------- Total: 342.05 [W/m²]	Reflected from the atmosphere: 107 [W/m²] Emitted by the Earth and its atmosphere towards space: 235.05 [W/m²] ------------- Total: 342.05 [W/m²]