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Assertion–Reason (Evaluate Truth and Explanation):\nAssertion (A): The average temperature of the Earth has been rising.\nReason (R): The greenhouse effect traps the Sun’s heat within the Earth’s atmosphere.

Difficulty: Easy

Both (A) and (R) are true, and (R) is the correct explanation of (A).
Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(A) is true, but (R) is false.
(A) is false, but (R) is true.
Both (A) and (R) are false.

Correct Answer: Both (A) and (R) are true, and (R) is the correct explanation of (A).

Explanation:

Introduction / Context:
This item links observed global warming to the greenhouse effect, a foundational climate concept.

Given Data / Assumptions:

(A) Multidecadal trend: rising global mean surface temperature.
(R) Greenhouse gases absorb and re-emit infrared radiation, trapping heat.

Concept / Approach:
The enhanced greenhouse effect, due to increased greenhouse gas concentrations, explains observed warming.

Step-by-Step Solution:

1) (A) True: long-term upward trend in global average temperature is well-documented.2) (R) True: greenhouse effect is a real physical mechanism.3) (R) causally explains (A): enhanced greenhouse forcing raises equilibrium temperatures.

Verification / Alternative check:
Short-term variability (e.g., ENSO) does not negate the long-term trend or the forcing mechanism.

Why Other Options Are Wrong:
They deny either the observation, the mechanism, or their causal connection.

Common Pitfalls:
Confusing weather variability with climate trends; ignoring radiative forcing basics.

Assertion–Reason (Evaluate Truth and Explanation):\nAssertion (A): The average temperature of the Earth has been rising.\nReason (R): The greenhouse effect traps the Sun’s heat within the Earth’s atmosphere.

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