EARTH'S RADIATION BUDGET — Planetary albedo fraction Question: Approximately what fraction of the Sun’s incoming radiation is reflected back to space by the Earth–atmosphere system (planetary albedo)?

Introduction / Context:
Planetary albedo is the proportion of incoming solar radiation reflected back to space by clouds, aerosols, atmospheric molecules, and Earth’s surface. It is a key control on global energy balance and climate sensitivity.

Given Data / Assumptions:

• We seek an approximate, commonly taught percentage for exams.
• The value includes reflection by clouds, air, and surface combined.
• Small variations occur seasonally and with cloud cover, but the benchmark value is stable enough for recall.

Concept / Approach:
Standard educational references often quote a planetary albedo near one-third. While many modern estimates center around ~30–31 percent, traditional textbooks and competitive-exam keys frequently accept a rounded figure in the mid-30s. Among the options given, 36 percent matches this conventional rounded figure.

Step-by-Step Solution:
Recall “about one-third” of solar radiation is reflected.Match to the closest listed value recognizing exam convention → 36 percent.Verify that the remaining energy (about two-thirds) is absorbed by the atmosphere and surface.

Verification / Alternative check:
Energy-budget diagrams typically show reflection breakdown: ~20 percent by clouds/atmosphere and ~10 percent by surface, totaling near one-third. Precise satellite-era values vary slightly but stay in this range.

Why Other Options Are Wrong:
47 percent — too high; would imply much lower global absorption than observed.17 percent — too low compared with cloud and surface reflection.None of the above/3 percent — far from accepted benchmarks.

Common Pitfalls:
Confusing planetary albedo (~30–36%) with surface albedo of specific terrains (e.g., fresh snow ~80–90%, ocean ~5–10%).

Final Answer:
36 percent