Difficulty: Easy
Correct Answer: blanketing effect of CO2 in the atmosphere.
Explanation:
Introduction / Context: Global warming refers to the long-term upward trend in Earth’s average surface temperature. Understanding the primary driver is essential for environmental management and policy.
Given Data / Assumptions:
Concept / Approach: Carbon dioxide and other greenhouse gases absorb outgoing longwave (infrared) radiation and re-emit it, creating a “blanketing” effect that warms the lower atmosphere and surface. While many activities (e.g., fossil fuel combustion, deforestation) influence concentrations, the greenhouse effect mechanism of CO2 is the central cause of progressive warming.
Step-by-Step Solution:
Link increased CO2 concentration to radiative forcing (positive).Recognize that automobile exhaust is a source of CO2 but is not the mechanism itself.Differentiate ozone layer issues from greenhouse warming.Select the blanketing effect of CO2 as the primary cause listed.Verification / Alternative check: Climate assessments attribute the majority of observed warming to anthropogenic greenhouse gases, with CO2 being the largest single contributor to radiative forcing.
Why Other Options Are Wrong:
Automobile exhaust: A source category, not the fundamental physical cause.De-forestation: Contributes by reducing CO2 sinks, but the option asked for the main cause; the greenhouse effect captures the mechanism directly.Thickening of ozone layer: Unrelated; ozone depletion and recovery are distinct from greenhouse warming.Common Pitfalls: Mixing sources with mechanisms; the correct answer emphasizes the physical greenhouse effect.
Final Answer: blanketing effect of CO2 in the atmosphere.
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