Greenhouse effect and global warming

Correct answer: A. Relatively more heat may remain at night

Explanation: Industrial regions can emit greenhouse gases and waste heat. Greenhouse gases absorb outgoing infrared radiation, while buildings and paved surfaces also store heat and release it slowly after sunset. These factors can contribute to warmer nights and an urban or industrial heat-island effect. The magnitude varies with weather, land cover and emissions.

Correct answer: B. Because it can reflect glacier melt and thermal expansion of seawater

Explanation: Sea-level rise is an important indicator because it records two major consequences of a warming climate. Land glaciers and ice sheets lose mass and add water to the oceans, while warmer seawater expands and occupies more volume. Although tides and local land movement also affect measurements, they do not explain the long-term global trend by themselves.

Correct answer: A. To assess climate science and provide scientific information for policy

Explanation: The Intergovernmental Panel on Climate Change, or IPCC, reviews and assesses published scientific research about climate change, its risks, impacts, adaptation, and mitigation. It does not conduct weather control or directly enforce laws. Its assessment reports help governments and institutions understand evidence and make informed climate policies, while the underlying research is produced by scientists worldwide.

Correct answer: A. Because it can reduce dependence on fossil-fuel combustion

Explanation: Renewable sources such as solar, wind, and sustainably managed hydropower generate energy without the continuous combustion of coal, oil, or natural gas. Replacing fossil fuels can therefore reduce carbon-dioxide emissions and other pollutants over the energy system’s life cycle. Renewable energy is not impact-free, but reducing greenhouse-gas emissions is precisely why it is classified as mitigation.

Correct answer: A. It can reduce warming by lowering emissions

Explanation: Energy efficiency means providing the same service, such as lighting, heating, transport, or production, with less energy input. If the saved energy would otherwise come from coal, oil, or gas, fuel consumption and associated greenhouse-gas emissions can decline. Efficiency does not automatically eliminate warming, because demand and rebound effects matter, but it is a major mitigation option.

Correct answer: A. An imbalance between crop seasons and water availability

Explanation: Global warming can alter temperature regimes, rainfall timing, snowmelt, evaporation, and the frequency of droughts or floods. As a result, the period suitable for sowing and harvesting may no longer match the availability of water, and crops may face heat stress during sensitive growth stages. The exact outcome differs by region, crop, and management, but seasonal and water imbalance is a direct risk.

Correct answer: A. Species distributions may shift, and coral reefs may come under stress

Explanation: A is correct. As the ocean warms, marine habitats change and some species shift their geographic ranges. Coral reefs are especially vulnerable: prolonged heat stress can cause bleaching, in which corals lose their symbiotic algae, and severe or repeated bleaching can kill them. Warming does not make oceans or tides disappear.

Correct answer: A. Local heat may become more intense

Explanation: A is correct. Less vegetation means less shade and evapotranspiration, so less heat is used to evaporate water and cool the area. Built surfaces and heat released by urban activity can add to local warmth; greenhouse-gas emissions also contribute to broader warming. The exact local effect depends on conditions such as land cover, wind and humidity.

Correct answer: A. Because it can alter the distribution of water and energy

Explanation: A is correct. A warmer atmosphere can hold more water vapour, which can contribute to heavier rainfall when that moisture condenses. Warming also changes evaporation, soil moisture and the movement of heat through the atmosphere and oceans. These changes can increase the likelihood or intensity of some heatwaves, heavy-rain events and droughts, though effects differ by event type and region.

Correct answer: A. Their intensity may increase because of a greater energy supply

Explanation: A is correct. Tropical cyclones draw energy from warm ocean water: evaporation supplies moisture, and condensation releases latent heat. Warmer sea-surface temperatures can provide more moisture and energy, potentially supporting stronger winds and rainfall when other conditions, such as atmospheric circulation and wind shear, are favourable. This does not mean every cyclone will intensify.

Correct answer: A. Human activities increase greenhouse-gas concentrations, strengthening heat retention

Explanation: The correct answer is A. The natural greenhouse effect occurs when gases such as water vapour and carbon dioxide absorb and re-emit some outgoing infrared radiation, helping keep Earth warm. Human activities raise the concentrations of greenhouse gases, strengthening this effect and shifting Earth’s energy balance toward warming.

Correct answer: A. Earth’s average surface temperature would be much lower, making liquid water and many life processes difficult to sustain

Explanation: The correct answer is A. The natural greenhouse effect retains some outgoing infrared energy in the atmosphere and surface system. Without it, Earth’s average surface temperature would be much lower, making liquid water and many processes that support life difficult to sustain. This does not mean that Earth would become exactly like the Moon or that its oceans would boil.

Correct answer: A. Expanding or restoring systems that absorb and store more carbon than they release

Explanation: The correct answer is A. A carbon sink absorbs more carbon dioxide from the atmosphere than it releases over a period. Protecting or restoring forests, wetlands, and carbon-rich soils can increase carbon storage. These actions complement emission reductions; they do not replace them, because stored carbon can be released again through events such as fires or land-use change.

Correct answer: B. Long-term climate trend

Explanation: A temperature change observed consistently over several decades represents a long-term climate trend. Weather describes short-term conditions over hours, days, or seasons, whereas climate is identified from long-period averages and patterns. Therefore, the time scale in the question clearly supports option B rather than a seasonal fluctuation or daily tidal cycle.

Correct answer: A. It can generally decrease because nights stay warmer

Explanation: The diurnal temperature range is the difference between daytime maximum and nighttime minimum temperature. Enhanced greenhouse gases absorb outgoing long-wave radiation and reduce nighttime cooling, so minimum temperatures may rise more strongly than maximum temperatures. The range can therefore decrease, although the exact response varies by place and weather conditions.

Correct answer: A. Greater absorption of infrared heat emitted by Earth

Explanation: Carbon dioxide is a greenhouse gas that absorbs part of the long-wave infrared radiation emitted by Earth’s surface and lower atmosphere. Increasing its concentration strengthens this heat-retaining process and contributes to warming. Changes in rainfall or ocean salinity may occur indirectly, but they are not the most immediate direct effect of added carbon dioxide.

Correct answer: A. Because more solar energy is absorbed

Explanation: Albedo is the fraction of incoming solar radiation reflected by a surface. When albedo decreases, less sunlight is reflected back to space and more solar energy is absorbed by the land, ocean, or atmosphere. The additional absorbed energy can raise temperatures. This is why melting snow and ice may create a warming ice-albedo feedback.

Correct answer: A. It can trap more heat even in small amounts

Explanation: Methane is a potent greenhouse gas. Molecule for molecule, it absorbs infrared radiation efficiently and has a much greater warming effect than carbon dioxide over a comparable period, although its atmospheric concentration is lower and its lifetime is shorter. Thus, small amounts can still have a significant climate effect.

Correct answer: A. Burning fossil fuels and deforestation

Explanation: Burning coal, oil, and natural gas releases carbon dioxide and other greenhouse gases. Deforestation both releases stored carbon and reduces the number of trees that remove carbon dioxide through photosynthesis. These human activities increase atmospheric heat trapping. Water vapour mainly acts as a feedback, increasing after warming rather than being the primary initial human forcing.

Correct answer: A. Thermal radiation emitted by Earth

Explanation: Longwave radiation is the relatively low-energy, long-wavelength infrared radiation emitted by Earth’s surface and atmosphere after they absorb solar energy and warm. It is also called terrestrial or outgoing radiation. Greenhouse gases absorb part of this radiation, whereas incoming solar radiation is mainly shortwave.

Correct answer: A. More heat escaping from the surface is trapped

Explanation: After sunset, Earth’s surface continues to lose energy mainly as longwave infrared radiation. Greenhouse gases absorb and re-emit part of this outgoing radiation, reducing the rate at which the surface cools at night. Consequently, nighttime minimum temperatures may rise and nights may feel warmer, even though there is no sunlight at night.

Correct answer: B. Greenhouse effect

Explanation: The greenhouse effect is the atmospheric process in which gases such as carbon dioxide and water vapour absorb and re-emit part of Earth’s outgoing longwave infrared radiation. This slows the loss of heat to space and warms the lower atmosphere and surface. Albedo concerns reflection, ozone depletion concerns ozone loss, and the Coriolis effect concerns moving air and water.

Correct answer: A. Increased burning of fossil fuels such as coal, oil, and natural gas

Explanation: Industrialisation greatly increased the use of coal, oil, and natural gas in factories, transport, and electricity generation. Their combustion releases carbon dioxide and other greenhouse gases, which increase absorption of outgoing infrared radiation and strengthen heat retention. Earth’s size, the Moon’s distance, and complete oxygen loss do not explain the observed modern warming trend.

Correct answer: A. Because albedo decreases

Explanation: Snow and ice reflect a large proportion of incoming sunlight and therefore have high albedo. When they melt, darker ocean water or land is exposed. These darker surfaces absorb more solar energy, causing additional warming and further melting. This self-reinforcing process is called the positive ice-albedo feedback.

Correct answer: A. Strengthening the initial change

Explanation: Positive feedback occurs when a climate response reinforces the original disturbance rather than opposing it. For example, warming melts reflective ice, lowers albedo, increases solar absorption, and produces still more warming. Thus the term “positive” means amplification, not necessarily a beneficial result. Negative feedback, in contrast, tends to reduce or stabilise the initial change.