The correct option is 35 units.
Explanation
Albedo refers to the proportion of the incident light or radiation that is reflected by a surface. In the context of the Earth's heat budget, it represents the total amount of incoming shortwave solar radiation that is reflected back into space without heating the Earth's surface or atmosphere.
Detailed Analysis
To understand the Earth's albedo, the total incoming solar radiation is assumed to be 100 units. The distribution is as follows:
- Reflected Radiation (Albedo): Approximately 35 units are reflected back to space before reaching the Earth's surface. This includes:
- 27 units reflected by clouds.
- 2 units reflected by snow and ice-covered areas.
- 6 units scattered by the atmosphere to space.
- Absorbed Radiation: The remaining 65 units are absorbed, contributing to the Earth's heat budget:
- 14 units absorbed within the atmosphere.
- 51 units absorbed by the Earth's surface.
Therefore, the reflected amount, or the albedo of the Earth, is approximately 35 units (or 35%).
Key Takeaway: The Earth's albedo is approximately 35% (35 units), representing the fraction of solar energy reflected back to space, while the remaining 65 units are absorbed by the atmosphere and the surface.