Question

What percentage of incoming solar radiation on earth is reflected back to space?

• A. 25
• B. 30
• C. 35
• D. 40

Hint:

Albedo is a dimensionless quantity ranging from 0 (perfect absorber) to 1 (perfect reflector).
The average albedo of Earth is approximately 0.30, which corresponds to a 30% reflection rate.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The fraction of incoming solar electromagnetic radiation reflected back into space by the Earth-atmosphere system is known as the planetary albedo.
This parameter is critical for understanding the global energy balance and regulating the Earth's average surface temperature.

Step 2: Detailed Explanation:
When solar radiation reaches the Earth's atmosphere, it interacts with various components:
1. Reflection by Clouds: Clouds are the largest contributors to the Earth's albedo, reflecting a significant portion of shortwave solar radiation back into space.
2. Scattering and Reflection by the Atmosphere: Atmospheric gases, aerosols, and dust particles scatter solar radiation in all directions, some of which escapes back into space.
3. Reflection by the Earth's Surface: Highly reflective surfaces on the Earth, such as snow-covered regions, glaciers, and deserts, reflect a portion of the transmitted solar energy directly back into space.
On average, the global planetary albedo of the Earth is measured to be approximately \( 30% \) to \( 31% \).
This means that out of \( 100 \text{ units} \) of incoming solar energy, about \( 30 \text{ units} \) are reflected back to space without heating the Earth's system.
The remaining \( 70% \) is absorbed by the atmosphere, oceans, and landmasses, driving the global climate system.

Step 3: Final Answer:
The percentage of incoming solar radiation reflected back to space is 30.