Greenhouse effect and global warming

Correct answer: A. Toward greater warming

Explanation: Positive radiative forcing means that the climate system receives more energy than it loses, creating an energy imbalance that tends to raise global temperature. Increased greenhouse gases usually produce positive forcing by reducing outgoing long-wave radiation. Negative forcing would favour cooling, but salinity and complete rainfall cessation do not define radiative forcing. Therefore A is correct.

Correct answer: A. It redistributes heat and moderates temperature

Explanation: Oceans absorb and store large amounts of solar energy, then exchange heat with the atmosphere through evaporation, radiation, and turbulent transfer. Ocean currents and winds redistribute this energy, reducing temperature extremes and influencing pressure, clouds, and rainfall. The exchange does not keep salinity constant or create equal rainfall everywhere. Therefore A is correct.

Correct answer: A. Absorption of heat and cloud formation may decrease

Explanation: Water vapour absorbs outgoing infrared radiation and participates in cloud formation. If water vapour decreases in the upper atmosphere, the absorption of long-wave heat and the formation of some high-level clouds may decrease, altering radiative balance. The effect is not an immediate direct change in ocean salinity, Earth’s axis, or incoming solar radiation. Thus A is correct.

Correct answer: A. Large temperature response even to small forcing

Explanation: Climate sensitivity describes how strongly Earth’s average temperature responds to a specified change in radiative forcing, often an increase in atmospheric carbon dioxide. Higher sensitivity means that the same forcing produces a larger temperature response, partly because of feedbacks involving water vapour, clouds, ice, and ecosystems. It does not mean weather becomes constant or rain stops, so A is correct.

Correct answer: A. Warming can intensify further

Explanation: Higher carbon dioxide strengthens the greenhouse effect by reducing the loss of outgoing infrared radiation. Lower albedo means that less incoming sunlight is reflected to space and more is absorbed by the Earth system. These two positive warming influences can reinforce one another, although the exact outcome also depends on clouds, aerosols, oceans, and other feedbacks. Therefore A is correct.

Correct answer: A. Because melting ice lowers albedo and causes greater absorption of solar energy

Explanation: Snow and ice reflect much incoming sunlight because they have high albedo. When warming melts them, darker ocean water or land is exposed; these surfaces absorb more solar energy, causing further warming and additional melting. This positive ice–albedo feedback contributes to Arctic amplification. The other options use inaccurate absolute claims, so A is correct.