Greenhouse effect and global warming

Correct answer: C. Infrared radiation

Explanation: Earth’s surface absorbs incoming solar energy and emits much of that energy back as long-wave infrared radiation. Greenhouse gases such as carbon dioxide, methane, and water vapor absorb portions of this outgoing infrared radiation and re-radiate it, slowing heat loss to space. They do not primarily trap sound waves or ordinary radio waves.

Correct answer: B. Earth’s average temperature

Explanation: Global warming means a long-term rise in Earth’s average near-surface temperature. It is mainly associated with the enhanced greenhouse effect caused by increased concentrations of gases such as carbon dioxide and methane. It does not mean that every place warms equally or that daily weather conditions are identical; weather and climate are related but different concepts.

Correct answer: C. Helping reduce greenhouse gases

Explanation: Solar, wind, and hydropower are renewable energy sources that can produce electricity with much lower direct greenhouse-gas emissions than coal, oil, or natural gas. Their use can reduce dependence on fossil fuels and help limit carbon dioxide emissions. They do not eliminate every environmental impact, but reducing emissions is an important benefit.

Correct answer: B. It can reduce emissions per person

Explanation: A bus, train, or metro can carry many passengers in one vehicle. When occupancy is reasonably high, the fuel consumed and greenhouse gases emitted per passenger may be lower than for separate private cars or two-wheelers. Public transport therefore supports lower per-person emissions, although its total benefit depends on vehicle efficiency, route, and passenger use.

Correct answer: B. Total greenhouse-gas emissions caused by a person, organisation, or activity

Explanation: A carbon footprint is the total greenhouse-gas emission associated directly and indirectly with a person, organisation, product, service, or activity. It includes emissions from energy use, transport, production, and sometimes the full life cycle of goods. Results are commonly expressed as carbon-dioxide equivalent, allowing different gases to be compared by warming effect.

Correct answer: D. Rise in global average temperature

Explanation: An increased concentration of greenhouse gases absorbs more of the infrared radiation emitted by Earth and re-radiates some of it back toward the surface. This reduces the rate at which heat escapes to space and creates an energy imbalance that raises global average temperature. Continued warming can contribute to glacier and polar-ice loss rather than immediate ice expansion.

Correct answer: A. Carbon dioxide emissions into the atmosphere

Explanation: Open burning of waste or dry leaves releases carbon dioxide, fine particles, smoke, and sometimes other harmful gases. Carbon dioxide is a greenhouse gas, so repeated burning can increase atmospheric emissions and contribute to the enhanced greenhouse effect. Burning also creates local air pollution; it is not a safe substitute for composting, recycling, or controlled waste treatment.

Correct answer: B. They consume less energy for the same task

Explanation: An energy-efficient appliance provides the same service while using less electricity or fuel than a conventional alternative. Lower energy demand can reduce fuel consumption at power stations, especially where electricity is generated from coal or gas, and therefore can lower greenhouse-gas emissions. Efficiency does not eliminate every type of pollution, so option C is an exaggeration.

Correct answer: A. Evaporation can increase

Explanation: Higher temperature generally increases the energy available for evaporation from oceans, lakes, soil, and vegetation. A warmer atmosphere can also hold more water vapour, which may change cloud formation, rainfall timing, and the intensity of heavy precipitation. The response is not identical everywhere, but increased evaporation is the most direct effect listed.

Correct answer: C. Methane

Explanation: Permafrost contains frozen organic matter from plants and animals that died long ago. When thawing occurs, microorganisms can decompose this material and release methane, particularly where oxygen is limited. Methane is a powerful greenhouse gas, so permafrost thaw can create a positive climate feedback: warming causes thawing, and released methane can contribute to further warming.

Correct answer: A. Heat stroke

Explanation: Excessive heat can raise the body’s internal temperature beyond its ability to regulate itself. This may cause heat exhaustion, dehydration, and, in severe cases, heat stroke, which is a medical emergency. Heat stroke can damage vital organs, so drinking water, avoiding intense midday heat, and seeking urgent medical help are important.

Correct answer: B. Concrete and less greenery

Explanation: Cities often contain extensive concrete, asphalt, and buildings that absorb and store solar heat during the day and release it slowly at night. They also have fewer trees and less open soil for shade and evaporative cooling. This combination produces the urban heat-island effect, making cities warmer than nearby rural areas.

Correct answer: B. Increase in the effect due to human activities

Explanation: The natural greenhouse effect keeps Earth warm enough for life, but human activities can intensify it. Burning coal, oil, and gas, clearing forests, agriculture, and industrial processes increase gases such as carbon dioxide and methane. These gases absorb more outgoing infrared radiation, changing Earth’s heat balance and causing global warming.

Correct answer: B. Because it retains some heat emitted by Earth in the atmosphere

Explanation: Earth’s surface absorbs solar energy and later emits energy mainly as infrared radiation. Greenhouse gases such as water vapour, carbon dioxide, and methane absorb some of this outgoing radiation and re-radiate it in different directions, including back toward the surface. Like a blanket, the atmosphere reduces heat loss, although it does not trap all heat or block sunlight completely.

Correct answer: C. It affects Earth’s heat balance

Explanation: Carbon dioxide is naturally present in the atmosphere and is also released by human activities. It absorbs part of the infrared radiation emitted by Earth, so it helps regulate the planet’s heat balance. A moderate natural greenhouse effect is essential for life, but a human-caused rise in CO2 strengthens heat retention and contributes to global warming.

Correct answer: C. Carbon absorption

Explanation: Trees absorb carbon dioxide during photosynthesis and use carbon to form leaves, stems, roots, and other biomass. Some carbon is also stored in soils. Consequently, planting and maintaining trees can strengthen carbon sinks and help reduce the growth of atmospheric CO2, although its effectiveness depends on tree survival, ecosystem conditions, and long-term protection.

Correct answer: B. Carbon dioxide

Explanation: Coal contains a large amount of carbon. During combustion, that carbon combines with oxygen to form carbon dioxide, especially when burning is relatively complete. Coal burning can also produce smoke, particulate matter, sulfur compounds, and nitrogen oxides, but CO2 is the principal greenhouse-gas emission relevant to global warming. Therefore, carbon dioxide is the best answer.

Correct answer: C. Methane

Explanation: Flooded paddy fields contain waterlogged soil with very little oxygen. Microorganisms called methanogens decompose organic matter under these anaerobic conditions and produce methane. Methane is a powerful greenhouse gas, so rice cultivation can contribute to climate change. Improved water management and alternate wetting and drying can reduce these emissions.

Correct answer: A. Carbon dioxide

Explanation: Cement production releases substantial carbon dioxide in two main ways. First, limestone is heated and chemically decomposes during calcination: calcium carbonate changes into lime and CO2. Second, fuels burned in kilns add further CO2. Other pollutants may occur, but carbon dioxide is the principal greenhouse-gas emission associated with cement manufacture.

Correct answer: C. Toward an increase

Explanation: If greenhouse-gas concentrations continue to rise, more outgoing infrared radiation will be absorbed by the atmosphere, producing a positive energy imbalance. The long-term global average temperature therefore tends to increase. Individual years can still be cooler or warmer because of natural variability, so a warming trend does not mean that every single year must be hotter than the previous one.

Correct answer: B. Mitigation and adaptation

Explanation: Mitigation means reducing the causes of climate change, for example by using renewable energy, improving efficiency, protecting forests, and lowering greenhouse-gas emissions. Adaptation means adjusting to unavoidable or expected impacts through heat planning, water conservation, resilient crops, and stronger infrastructure. Effective climate action requires both approaches together.

Correct answer: A. Carbon absorption can increase

Explanation: Forests remove carbon dioxide from the atmosphere through photosynthesis and store carbon in trunks, roots, leaves, and soil. Protecting existing forests prevents this stored carbon from being released through burning or decay and preserves an important carbon sink. Forest protection also supports biodiversity, water regulation, and local climate moderation, although it cannot control every climate process.

Correct answer: A. Coastal areas

Explanation: Increasing heat contributes to thermal expansion of seawater and melting of land ice, both of which can raise sea level. Coastal areas may consequently face more frequent flooding, erosion, saltwater intrusion, storm-surge damage, and displacement of settlements. Although mountains and deserts also experience climate risks, the question asks for an area particularly exposed to sea-level-related impacts.

Correct answer: B. It may increase

Explanation: Higher temperature gives water molecules more kinetic energy, allowing more of them to escape from the liquid surface into the air. Therefore, evaporation generally increases when other conditions, especially humidity and wind, are comparable. The actual rate also depends on surface area, wind speed, and atmospheric moisture, so temperature is important but not the only controlling factor.

Correct answer: A. Release of methane into the atmosphere

Explanation: When permafrost thaws, previously frozen organic material becomes available for microbial decomposition. In oxygen-poor conditions, this process can release methane, while other conditions may also produce carbon dioxide. Methane is a strong greenhouse gas, so thawing can create a positive feedback: warming causes thawing, and released gases cause additional warming.