Explanation

Solar energy reaches the Earth predominantly as short-wave radiation (insolation), to which the atmosphere is largely transparent. Out of 100 units of incoming solar radiation, roughly 35 units are reflected directly back into space without heating the system (the Earth’s albedo—27 from clouds, 2 from ice/snow, and 6 by scattering). Of the remaining 65 units, only 14 units are absorbed directly by the atmosphere, while 51 units warm the Earth’s surface. As the surface cools, it re-radiates this energy outward as long-wave terrestrial radiation (infrared). The atmosphere absorbs 34 units of this terrestrial radiation, meaning it is fundamentally heated from the ground up rather than from direct solar rays.

* Statement I — Incorrect: The atmosphere is primarily heated by long-wave terrestrial radiation, not by incoming solar radiation. While direct solar insolation contributes only a small fraction (about 14 units) to atmospheric heating, outgoing radiation emitted by the Earth’s surface accounts for the major share (about 34 units).

* Statement II — Correct: Atmospheric greenhouse gases—primarily carbon dioxide (CO₂), water vapour (H₂O), methane (CH₄), nitrous oxide (N₂O), and ozone (O₃)—are optically selective. While largely transparent to incoming short-wave solar radiation, their molecular structures make them exceptionally good absorbers of long-wave terrestrial radiation, trapping thermal energy and re-radiating it to drive the greenhouse effect.

Hence, Option (d) is the correct answer.