Nearly 30% of the solar radiations return back to the space without contributing anything to the earth's surface temperature. This amount of radiation is known as—

The amount of solar radiation reflected back to space without contributing to the Earth's surface temperature is known as the Earth's albedo [2]. Albedo is defined as the fraction or proportion of incoming solar radiation that a surface reflects [1]. On a global scale, this is often referred to as the planetary albedo. While specific values can vary slightly across sources, it is generally estimated that approximately 30% to 35% of incoming solar energy is reflected back to space by clouds, atmospheric particles, and reflective surfaces like snow and ice [5]. Specifically, the Earth's average planetary albedo is approximately 0.30 to 0.31, meaning about 30-31% of the sun's energy is immediately reflected. In contrast, a black body is a theoretical object that absorbs all radiation, while the tropopause and mesopause are boundaries within the Earth's atmospheric layers.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > Albedo > p. 283
2. [2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Heat Budget of the Planet Earth > p. 69
3. [4] https://mynasadata.larc.nasa.gov/mini-lessonactivity/what-albedo
4. [5] https://www.nature.com/scitable/knowledge/library/the-global-climate-system-74649049/