Greenhouse effect and global warming

Forests cool the surface through shade and evapotranspiration, and they remove carbon dioxide from the atmosphere through photosynthesis. Deforestation reduces both cooling and carbon uptake; burning or decomposition may also release stored carbon. Consequently, local and regional warming can increase, while the cooling and carbon-sink functions of forests decline. Thus A is correct.

Human activities release large quantities of greenhouse gases when coal, oil, and gas are burned for electricity, heating, industry, and transport. Power generation and transport are therefore major anthropogenic emission sectors, especially for carbon dioxide. Weathering, river flow, and tides are mainly natural processes and are not the best answer to a question about human emissions. Hence A is correct.

Concrete, asphalt, roofs, and other urban materials absorb and store solar heat, while fewer trees reduce shade and evaporative cooling. Waste heat from vehicles, buildings, and industry can add to this effect. Consequently, built-up areas may become warmer than nearby rural surroundings, producing an urban heat island. Urbanization does not alter Earth’s orbit or axial tilt, so A is correct.

Polar amplification means that the Arctic and Antarctic regions warm faster than the global average. Melting snow and sea ice reduce surface albedo, so darker land or water absorbs more solar energy. This positive feedback intensifies regional warming. The term describes a relative rate of warming, not the fact that the poles remain cold.

Long records from ice cores, ocean sediments, tree rings, and modern instruments show a strong long-term relationship between atmospheric carbon dioxide and global temperature. Carbon dioxide absorbs outgoing infrared radiation and strengthens the greenhouse effect. Short-term variations may have several causes, but they do not cancel the established long-term climate relationship.

Outgoing longwave radiation is thermal infrared energy emitted by Earth toward space. Greenhouse gases absorb part of this radiation and re-emit it in different directions, reducing the rate at which heat escapes. Studying it therefore reveals Earth’s heat balance and explains how atmospheric gases influence surface temperature. The other options describe unrelated quantities.

The governing distinction is between adaptation and mitigation. Climate adaptation means adjusting human activities, systems or practices to actual or expected climate impacts, thereby reducing vulnerability. Changing sowing dates when rainfall patterns shift helps farmers work with the new seasonal conditions, so option A is adaptation. Using solar energy to reduce greenhouse-gas emissions addresses the cause of climate change and is therefore mitigation, not adaptation. Increasing fossil-fuel use and uncontrolled deforestation intensify emissions and environmental damage. The answer is thus A because it describes adjustment to a climate impact rather than prevention of its underlying cause.

The governing concept is climate mitigation, which means reducing the causes of climate change, especially greenhouse-gas emissions or the removal of carbon sinks. Increasing solar, wind or other renewable-energy use can reduce dependence on coal, oil and gas and therefore lower emissions from energy production. Raised houses, drought-resistant crops and cyclone shelters do not primarily reduce emissions; they reduce exposure or damage from floods, droughts and storms, so they are adaptation measures. The wording “mitigation” is therefore decisive: option A addresses the source of the problem, whereas options B, C and D address its impacts.