EARTH’S ENERGY BUDGET

EARTH’S ENERGY BUDGET

Earth’s energy budget represents the balance between the energy the planet receives from the Sun and the energy it radiates back into space. While smaller energy sources like Earth’s internal heat are considered, solar energy is the primary contributor.

Insolation:

The primary source of energy injected into Earth’s atmosphere is the Sun. Solar radiation, also called insolation, is constantly emitted in all directions. It is the electromagnetic energy radiating from the Sun.

• Imbalance in the Energy Budget: Imbalances in the energy budget occur when there is a mismatch between the incoming energy from the Sun and the outgoing energy radiated by the Earth. This imbalance can vary with seasonal changes and atmospheric composition.
• Factors Influencing Insolation: Several factors influence how much solar energy (insolation) is received by the Earth:

• Rotation of the Earth on its axis: The Earth’s axis is tilted at an angle of 66.5°, which affects the amount of insolation different places receive based on latitude.
• Angle of Incidence of the Sun’s Rays: Depending on the latitude, the angle at which sunlight strikes the surface varies. Higher latitudes receive sunlight at a more oblique angle, reducing the amount of insolation.
• Duration of the Day: The length of the day changes across different places and seasons, affecting the total amount of insolation received. Longer days allow for more insolation.
• Transparency of the Atmosphere: Factors like cloud cover, dust particles, water vapor, and atmospheric thickness influence the amount of solar radiation that reaches Earth’s surface.

Earth Energy Budget: Of the total solar energy entering Earth’s atmosphere:

• 50% is absorbed by Earth’s surface (land and oceans).
• 30% is reflected back into space by clouds, gases, and particles in the atmosphere.
• 20% is absorbed by the atmosphere and clouds.

 Natural Factors Influencing Earth’s Energy Budget:

• Insolation and Its Influencing Factors: The amount of solar energy received by Earth (insolation) is a key factor influencing the energy budget. Factors such as distance, wavelength, and particle characteristics (size, shape, and density) play a role.
• Atmospheric Aerosols: Molecules in the atmosphere scatter radiation, depending on the size and density of the particles, which influences the energy absorbed or reflected back into space.
• Greenhouse Gases (GHGs): A significant portion of energy is absorbed by GHGs such as methane (CH₄), nitrous oxide (NO₂), carbon dioxide (CO₂), ozone (O₃), and water vapor. These gases trap solar energy and re-radiate it back to Earth, helping maintain a habitable temperature.
• Surface Albedo: Albedo refers to the reflectivity of Earth’s surface. A high albedo means more sunlight is reflected, reducing heat absorption. Surfaces like ice and snow have high albedos, while darker surfaces absorb more heat.
• Clouds: Thicker and denser clouds reflect more sunlight, reducing the amount of energy absorbed by Earth’s surface.
• Vegetation: Dense vegetation absorbs more heat and releases moisture through evapotranspiration, which also affects the overall energy budget.

Anthropogenic (Human-Caused) Factors:

• Expansion of Agriculture: Intense agriculture in specific areas leads to increased heat absorption and affects the energy budget of Earth.
• Land Use Patterns: Urbanization and the development of urban heat islands directly contribute to altering the energy balance due to increased heat absorption.
• Industrialization: The burning of fossil fuels due to increasing industrial activity contributes to higher greenhouse gas emissions, which trap more heat in Earth’s atmosphere.
• Deforestation: Deforestation reduces vegetation cover, which would normally reflect solar energy or absorb it for evapotranspiration. This reduction leads to more energy being absorbed and affects the energy budget.

Significance of Earth’s Energy Budget:

• Global Warming and Cooling: When the incoming and outgoing energy fluxes are balanced, Earth remains in radiative equilibrium, leading to climate stability. If more energy is received than released, global warming occurs. Conversely, when more energy is emitted than absorbed, global cooling happens.
• Causes of Warming and Cooling: By studying Earth’s heat budget, scientists can understand changes in climate caused by natural phenomena (like volcanic eruptions) and human activities (such as industrial emissions).
• Disturbance in the Energy Budget: According to a recent IPCC report, human activities have caused approximately 1.0°C of global warming above pre-industrial levels. This has led to changes such as increased mean temperatures, extreme weather events, and unpredictable precipitation patterns across the globe. These changes lead to:

• Threats to Human Security: Increased frequency of heatwaves, floods, cyclones, and other extreme weather events.
• Food Insecurity: Declining crop yields due to higher temperatures, new pests, and diseases.
• Threat to Economic Growth: Disruptions in agriculture and industries due to extreme weather affect national economies.
• Threat to Small Island Nations: Rising sea levels due to melting ice threaten the existence of small islands and low-lying coastal regions.