Greenhouse effect and global warming

Correct answer: A. Crop duration may change

Explanation: Warmer temperatures can alter the rate at which crops develop, so sowing, flowering, maturation, and harvesting dates may shift. Changes in rainfall, heat waves, water availability, pests, and extreme events can further affect yields. The exact outcome differs by crop and location; warming may lengthen one crop’s season but shorten another’s or reduce productivity.

Correct answer: A. Dehydration

Explanation: During hot conditions the body loses water and salts through sweating. If these fluids are not replaced, dehydration may cause thirst, weakness, headache, dizziness, confusion, and reduced physical performance. Severe heat can progress to heat exhaustion or heat stroke. Frostbite and hypothermia are primarily cold-related conditions, while night blindness has a different nutritional cause.

Correct answer: A. Energy consumption

Explanation: Energy-efficient building design can use orientation, shading, insulation, natural ventilation, daylight, efficient appliances, and reflective materials to reduce heating, cooling, and lighting requirements. Lower energy demand usually means fewer fossil fuels are burned in power generation, reducing both operating costs and greenhouse-gas emissions. Building design cannot control tectonic or oceanic processes.

Correct answer: B. Earth’s heat balance can change

Explanation: Greenhouse gases absorb part of the infrared radiation emitted by Earth. If their concentration increases, the atmosphere can retain more energy, changing the balance between incoming solar energy and outgoing terrestrial radiation. This creates a tendency toward warming and can influence rainfall and circulation, but it does not mean that oceans always freeze or that rain stops everywhere.

Correct answer: A. Because trees absorb carbon dioxide and help reduce greenhouse gases

Explanation: Trees remove carbon dioxide from the atmosphere through photosynthesis and store carbon in vegetation and soil. Preventing deforestation therefore protects existing carbon sinks and avoids the emissions produced when forests are burned or decomposed. Forests also support biodiversity, soil protection, and water regulation. Their conservation is an important mitigation measure, although it cannot eliminate all greenhouse-gas emissions alone.

Correct answer: C. Tree plantation

Explanation: Planting and maintaining trees increases the amount of vegetation that can absorb carbon dioxide during photosynthesis. Carbon is incorporated into plant tissues and may also be stored in soil, creating or strengthening a carbon sink. Deforestation removes this capacity, while burning coal or plastic releases carbon dioxide and other pollutants rather than increasing atmospheric carbon absorption.

Correct answer: A. Saving electricity

Explanation: Saving electricity reduces the amount of power that must be generated. Where electricity is produced by coal, oil, or gas, lower demand means less fuel combustion and fewer carbon dioxide emissions. The exact benefit depends on the electricity mix, but conserving energy is generally a useful mitigation habit. Idling engines, excessive cooling, and open waste burning increase fuel use or pollution.

Correct answer: A. Extreme weather events

Explanation: An enhanced greenhouse effect warms the climate system and changes the movement of energy and moisture through the atmosphere. This can raise the likelihood or intensity of some heat waves, heavy rainfall, droughts, and storms, although the exact effect differs by region and hazard. It does not control moonlight, the length of rainbows, or the number of days in a year.

Correct answer: A. More frequent flooding in coastal areas

Explanation: When sea level rises, high tides and storm surges start from a higher baseline. As a result, low-lying coastal land and settlements can be flooded more often, even during moderate storms. Other important impacts include shoreline erosion and saltwater intrusion into groundwater and farmland. Mountain formation and changes in the Sun’s temperature are unrelated to sea-level rise.

Correct answer: A. Using energy-efficient appliances

Explanation: Energy-efficient appliances provide the same service while consuming less electricity. When electricity is generated by coal or other fossil fuels, lower demand reduces fuel combustion and therefore carbon-dioxide emissions. The other choices increase pollution or fossil-fuel use. Energy conservation is an important mitigation measure against global warming.

Correct answer: A. It can affect Earth's energy balance

Explanation: Long-term climate change can alter Earth’s energy balance by changing how much incoming solar energy is absorbed and how much outgoing infrared energy is retained. This can influence temperature, rainfall, ice, sea level, and ecosystems. The other choices are scientifically false or exaggerated descriptions of climate change.

Correct answer: A. Adopting renewable energy

Explanation: Renewable sources such as solar and wind produce electricity without directly burning coal, petroleum, or natural gas. Replacing fossil-fuel energy with renewable energy can therefore reduce carbon-dioxide emissions, especially when combined with efficiency and storage. Burning more petrol, wood, or waste generally adds pollutants and greenhouse gases.

Correct answer: A. Absorption and re-emission of outgoing infrared radiation by greenhouse gases in the atmosphere

Explanation: Greenhouse gases, including carbon dioxide, methane, and water vapour, absorb infrared radiation emitted by Earth’s warmed surface. They then re-emit radiation in different directions, including back toward the surface, slowing heat loss to space. This natural process warms the lower atmosphere; enhanced concentrations intensify warming.

Correct answer: A. Long-term rise in Earth's average temperature

Explanation: Global warming means a sustained increase in Earth’s average surface temperature over a long period. It is mainly associated with the enhanced greenhouse effect caused by rising concentrations of gases such as carbon dioxide and methane. It does not mean that every place becomes equally hot or rainy, nor that winds stop.

Correct answer: C. Carbon dioxide

Explanation: Carbon dioxide is a major greenhouse gas because its molecules absorb specific wavelengths of outgoing infrared radiation and re-emit energy, contributing to atmospheric warming. Human activities such as burning coal, oil, and gas increase its concentration. Oxygen, nitrogen, and helium do not significantly absorb terrestrial infrared radiation in the same way.

Correct answer: B. Carbon dioxide

Explanation: Coal and petrol contain carbon. During combustion, this carbon combines with oxygen to form carbon dioxide, so burning fossil fuels raises atmospheric CO₂. The additional CO₂ absorbs outgoing infrared radiation and strengthens the enhanced greenhouse effect. Oxygen is consumed in combustion, while nitrogen and argon are not the expected combustion product.

Correct answer: A. Carbon dioxide absorption from the atmosphere decreases

Explanation: Forests act as carbon sinks because growing trees remove carbon dioxide through photosynthesis and store carbon in biomass and soil. Deforestation reduces this uptake, and burning or decomposition of cleared vegetation can release additional CO₂. The resulting increase in atmospheric greenhouse gases can intensify global warming.

Correct answer: A. Keeping Earth at a habitable temperature

Explanation: The natural greenhouse effect absorbs and re-emits part of Earth’s outgoing infrared radiation, keeping the surface and lower atmosphere warmer than they would otherwise be. This moderate temperature allows liquid water and supports life. The enhanced greenhouse effect caused by human emissions is harmful, but the natural effect is essential.

Correct answer: A. It retains heat

Explanation: Water vapour absorbs and re-emits infrared radiation, so it helps retain heat in the atmosphere and is an important part of the natural greenhouse effect. Its amount changes through evaporation, condensation, and precipitation. Water vapour is mainly a feedback to warming rather than the original long-term human forcing in the way carbon dioxide is.

Correct answer: A. Sea level rise

Explanation: When land-based glaciers and ice sheets melt, their water flows into the oceans and increases ocean volume. Warming also causes seawater to expand thermally, adding to sea-level rise. Higher sea levels increase coastal flooding, erosion, and salt-water intrusion. Floating sea ice melting does not raise sea level in the same direct way.

Correct answer: C. Infrared

Explanation: Earth’s surface absorbs much incoming solar energy and releases it mainly as long-wave infrared radiation. Greenhouse gases absorb portions of this outgoing infrared radiation and re-emit it, including back toward the surface. This reduces the rate of heat loss to space. Therefore, infrared radiation, not ultraviolet or X-rays, is the correct answer.

Correct answer: A. Agriculture

Explanation: Global warming can change temperature patterns, rainfall timing, drought frequency, growing seasons, and the distribution of pests and diseases. These changes directly affect crop growth, irrigation needs, yields, and food security. The colour of rocks, the Sun’s size, and the taste of the sea are not normal direct effects of global warming.

Correct answer: A. Concrete surfaces and less greenery

Explanation: Concrete, asphalt, and buildings absorb and store solar energy, then release it slowly, especially after sunset. Cities also have less vegetation, so there is less shade and less evaporative cooling. Traffic, air conditioners, and industry add waste heat. Together these factors produce the urban heat-island effect.

Correct answer: B. Reducing the severity of a problem

Explanation: Mitigation means actions that reduce the causes or severity of a problem. In climate policy, it mainly refers to reducing greenhouse-gas emissions or increasing their removal through energy efficiency, renewable energy, and forest protection. Adaptation is different: it means adjusting to impacts that are already occurring or expected.

Correct answer: A. Methane

Explanation: Ruminant animals such as cattle, buffalo, and sheep digest plant material through microbial fermentation in their stomachs. This process produces methane, which is released mainly through belching and also from manure. Methane is a potent greenhouse gas, so livestock digestion contributes to agricultural emissions and climate change.