The Sun gives Earth energy in the form of short-wave radiation—this is called insolation. Earth also gives off energy as heat (long-wave radiation), just like any warm object. This outgoing energy is called terrestrial radiation.

Even though energy is always coming in and going out, Earth’s average temperature stays steady. That’s because there is a balance between the energy coming in and the energy going out. This balance is called the Earth’s Heat Budget.

The main source of energy for the Earth's climate system is incoming solar radiation. The sun emits energy in the form of shortwave radiation, which is absorbed by the Earth's atmosphere and surface. This absorbed energy is then re-emitted as longwave radiation, also known as infrared radiation.

The Earth's atmosphere and surface absorb different amounts of incoming solar radiation depending on their composition and structure. The Earth's atmosphere absorbs a significant amount of ultraviolet radiation (harmful to living organisms), while the Earth's surface absorbs a significant amount of visible and infrared radiation, which drives the planet's climate and weather patterns.

The energy absorbed by the Earth's atmosphere and surface is re-emitted as longwave radiation, which is then emitted back into space. This outgoing longwave radiation is critical in regulating the Earth's temperature and is influenced by atmospheric composition, cloud cover, and surface temperature.

The concentration of greenhouse gases plays a crucial role by trapping some of the outgoing longwave radiation and re-radiating it back towards the surface. This results in an increase in the Earth's average temperature, known as the greenhouse effect.

Even though the Sun is the main source of heat, the air gets cooler at higher altitudes. The atmosphere is heated through four main processes:

1. Radiation

• Heat travels as waves, even through empty space.
• The Sun sends shortwave energy to Earth (insolation).
• Earth gives back heat to the atmosphere as long waves.

Facts about radiation:

1. Everything (hot or cold) gives off radiant energy.
2. Hotter objects release more energy.
3. Hotter objects give off shorter waves.
4. Earth receives heat in short waves and sends it back in long waves.

2. Conduction

• Heat moves from the hot Earth’s surface to the air touching it.
• It happens only near the surface, where air touches the ground.
• Example: A spoon gets hot when left in a hot pot.

3. Convection

• After air near the surface gets hot (by conduction), it rises upward.
• This movement of hot air going up and cool air coming down is called convection.
• It keeps mixing the air and spreads heat in the lower atmosphere.

4. Advection

• This is the sideways movement of heat through wind.
• Wind moves warm or cool air from one place to another.
• Example: Sea breeze is cool wind moving from sea to land during daytime.

Cloud Cover

Cloud cover influences the amount of incoming solar radiation that reaches the surface and the amount of outgoing longwave radiation emitted back into space. Clouds reflect a significant portion of incoming solar radiation back into space, reducing the amount of energy absorbed by the surface. Clouds also trap a portion of outgoing longwave radiation, resulting in an increase in the amount of energy re-radiated back towards the surface.

Surface Temperature

The Earth's surface temperature is influenced by incoming solar radiation, cloud cover, and atmospheric composition. It affects the amount of energy absorbed and re-emitted as longwave radiation. Land masses tend to heat up and cool down more quickly than water masses, resulting in a more variable surface temperature.

Ocean Currents

Ocean currents play a crucial role by transporting heat and moisture around the planet. Driven by differences in temperature and salinity, they regulate the Earth's climate by transporting heat from the equator to the poles.

The Earth's heat budget plays a critical role in determining the planet's climate and weather patterns. The balance between incoming solar radiation and outgoing longwave radiation, along with the influence of cloud cover, surface temperature, and ocean currents, contributes to the formation of global climate patterns.

The presence of greenhouse gases results in an increase in the Earth's average temperature, leading to global warming and potential climatic disasters such as sea level rise, hurricanes, and droughts. Understanding the Earth's heat budget is essential for predicting, preparing for, and mitigating these effects.