Consider the following statements.
a. The temperature of the troposphere generally decreases with increasing altitude.
b. The troposphere is heated not by absorption of incoming short wave solar radia

Question

Consider the following statements.
a. The temperature of the troposphere generally decreases with increasing altitude.
b. The troposphere is heated not by absorption of incoming short wave solar radiation but by transfer of heat from the earth's surface.
Now state whether :

UnlockIAS · Accepted Answer

Correct — option (1), both statements a and b are correct, and b is the correct explanation of a. Statement a records the defining feature of the troposphere: temperature falls as altitude rises, at an average environmental lapse rate of about 6.5°C per kilometre, all the way up to the tropopause (roughly 8 km over the poles, 18 km over the equator), where the fall stops and the stratosphere begins. Statement b gives the mechanism that produces exactly this pattern. Incoming short-wave solar radiation passes through the largely transparent atmosphere with only modest direct absorption; it is the earth's solid and liquid surface that absorbs most of that radiation and warms up, and the surface then re-radiates energy as long-wave (terrestrial, infrared) radiation and transfers heat upward into the air immediately above it by conduction, and further up by convection as warmed parcels of air rise. Because the primary heat source is the ground rather than the sun acting directly on the air, the layer of atmosphere closest to the surface is warmest, and air gets progressively cooler the further it sits from that source — which is precisely the decrease in temperature with altitude described in statement a. Since b identifies the actual physical cause of the pattern a describes, b is the correct explanation of a, and option (1) is the only choice that captures both the truth of each statement and the explanatory link between them.

Why the other options are wrong — (b) Both statements are standard, well-established atmospheric science, not doubtful claims. The decrease of temperature with altitude in the troposphere (the environmental lapse rate) is a directly measured, textbook fact, and the earth's-surface heating mechanism behind it is equally well established — the atmosphere is heated predominantly from below, by terrestrial radiation and surface heat transfer, not by direct absorption of sunlight passing through it. Declaring both statements wrong ignores basic, settled physical geography.  (c) This gets the individual truth of both statements right but breaks the causal link between them for no good reason. Statement b is not an unrelated fact sitting alongside statement a — it is the mechanism that produces the very pattern statement a describes. If the atmosphere near the ground receives most of its heat from the surface below rather than from the sun directly, then air further from the surface necessarily receives less of that heat and is cooler, which is exactly the temperature-with-altitude relationship in statement a. Denying the explanatory connection here misses the point the pair of statements is built to test.  (d) Statement a is indeed correct, but statement b is not the false one here — it is also correct, and is in fact the mechanism behind statement a. The claim that the troposphere is heated primarily by the earth's surface rather than by direct absorption of incoming short-wave solar radiation is standard physical geography: short-wave radiation passes through the atmosphere with limited absorption, while the surface absorbs strongly and re-radiates long-wave heat upward. Marking this statement false discards a true and important fact.

Concept: The troposphere is the lowest layer of the atmosphere, extending from the surface up to the tropopause, and it is where almost all weather occurs. Its defining thermal property is the environmental lapse rate — temperature falling by roughly 6.5°C for every kilometre gained in altitude — and this happens because the troposphere is heated chiefly from below, by the earth's surface, rather than directly by the sun. Incoming short-wave solar radiation is largely transparent to the gases of the lower atmosphere and passes through with comparatively little direct absorption; it is the ground and oceans that absorb the bulk of it, warm up, and then transfer that heat back into the air above by conduction, convection and long-wave (terrestrial) radiation. This 'heated from below' mechanism is why the air closest to the surface is warmest and why temperature declines steadily with height through the troposphere.

State PCS 2025 Q23 — Geography PYQ with Answer

State PCS 2025 Q23 — Geography PYQ with Answer