How does the greenhouse effect work, and how are humans changing the climate?
Explain the greenhouse effect and the role of greenhouse gases, distinguish natural from human-enhanced climate change, and describe the evidence for and consequences of recent global warming.
A Regents answer on the greenhouse effect and climate change: how greenhouse gases (carbon dioxide, methane, water vapor) trap outgoing infrared energy and warm the surface, natural versus human-enhanced warming from burning fossil fuels, the evidence (rising carbon dioxide and temperature, melting ice, rising seas) and consequences, with worked exam questions.
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What this topic is asking
The Regents (and the new Earth and Space Sciences exam) wants you to explain the greenhouse effect and the role of greenhouse gases, to distinguish the natural greenhouse effect from human-enhanced warming, and to describe the evidence for and consequences of recent global warming. The mechanism, short-wave energy in, long-wave energy trapped, is the key.
How the greenhouse effect works
The crucial detail the Regents tests: greenhouse gases let short-wave energy in but absorb long-wave energy on its way out. The most abundant gases (nitrogen and oxygen) are not greenhouse gases; it is the trace gases that trap heat.
Natural versus human-enhanced
The evidence for recent warming
The Regents expects you to cite lines of evidence:
- Rising atmospheric carbon dioxide, tracked directly and matching the rise of industrial fossil-fuel use.
- Rising global average temperature over the past century-plus.
- Melting glaciers and ice sheets and shrinking Arctic sea ice.
- Rising sea level (from melting ice and the thermal expansion of warming water).
- Shifting seasons, growing zones and species ranges.
Consequences
The consequences span Earth's systems: sea-level rise threatens coasts; more frequent or intense extreme weather; shifting climate and growing zones; melting ice and changing ocean conditions; and stress on ecosystems and food and water supplies. Reducing the harm means cutting greenhouse-gas emissions (renewable energy, efficiency) and protecting carbon sinks such as forests.
Try this
Q1. Name two greenhouse gases. [1 point]
- Cue. Any two of carbon dioxide, methane, water vapor.
Q2. Explain how greenhouse gases warm the surface. [2 points]
- Cue. They let short-wave solar energy in, then absorb the long-wave (infrared) energy the surface radiates back out and re-emit some toward the surface, trapping heat.
Exam-style practice questions
Practice questions written in the style of NYSED exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Regents (style)1 marksPart A. Which gas is the main human-released greenhouse gas driving recent global warming? (1) nitrogen (2) oxygen (3) carbon dioxide (4) argon. Justify your choice.Show worked answer →
A 1-point multiple-choice question. The answer is (3).
Carbon dioxide, released mainly by burning fossil fuels, is the principal greenhouse gas behind recent warming; it absorbs and re-emits outgoing infrared (long-wave) energy, trapping heat near the surface. Nitrogen (1) and oxygen (2) make up most of the air but are not greenhouse gases, and argon (4) is inert. The trap is choosing nitrogen or oxygen because they are most abundant; abundance does not make a gas a greenhouse gas.
Regents (style)3 marksPart C. (a) Explain how the greenhouse effect warms Earth's surface. (b) Explain how burning fossil fuels enhances this effect. (c) State two lines of evidence that Earth's climate is currently warming.Show worked answer →
A 3-point extended-response question.
(a) 1 point: incoming solar (short-wave) energy is absorbed by the surface, which re-radiates it as infrared (long-wave) energy; greenhouse gases absorb this outgoing infrared and re-emit some back toward the surface, keeping it warmer than it would otherwise be.
(b) 1 point: burning fossil fuels releases extra carbon dioxide, increasing the concentration of greenhouse gases, which traps more outgoing energy and enhances the warming.
(c) 1 point: any two of: rising atmospheric carbon dioxide concentration, rising global average temperature, melting glaciers and ice sheets, shrinking sea ice, rising sea level, shifting seasons or species ranges.
Markers reward the short-wave-in/long-wave-trapped mechanism, the extra carbon dioxide from fossil fuels, and two valid lines of warming evidence.
Related dot points
- Describe how carbon cycles among the atmosphere, biosphere, hydrosphere and geosphere through photosynthesis, respiration, decomposition and combustion, and explain how human activities alter the carbon cycle.
A Regents answer on the carbon cycle: how carbon moves among the atmosphere, biosphere, hydrosphere and geosphere through photosynthesis, respiration, decomposition and combustion, the role of carbon sinks (oceans, forests, fossil fuels), and how burning fossil fuels and deforestation move stored carbon into the air, with worked exam questions.
- Explain how human activities (pollution, deforestation, land use, resource extraction) affect Earth's atmosphere, hydrosphere, geosphere and biosphere, and evaluate ways to reduce harm.
A Regents answer on human impact: how pollution, deforestation, land use and resource extraction affect the atmosphere, hydrosphere, geosphere and biosphere, examples such as air and water pollution, soil erosion and habitat loss, the idea of Earth's interconnected systems, and how to evaluate solutions, for the Earth and Space Sciences exam, with worked exam questions.
- Distinguish renewable from non-renewable energy resources, describe the main sources (fossil fuels, nuclear, solar, wind, hydro, geothermal) and weigh their advantages and environmental costs.
A Regents answer on energy resources: the difference between renewable and non-renewable resources, the main sources (coal, oil and gas, nuclear, solar, wind, hydroelectric, geothermal), how fossil fuels form over geologic time, and the advantages and environmental costs of each for the Earth and Space Sciences exam, with worked exam questions.
- Describe the layered structure and composition of the atmosphere and explain how energy is transferred by radiation, conduction and convection, including how surfaces absorb and reflect insolation.
A Regents answer on the atmosphere and energy transfer: the layered structure (troposphere to thermosphere) and temperature profile on the Reference Tables, the composition (nitrogen, oxygen, trace gases), the three modes of heat transfer (radiation, conduction, convection), and how surface color and texture affect the absorption and reflection of insolation, with worked exam questions.
- Explain the factors that control climate (latitude, elevation, proximity to water, ocean currents, mountain barriers and prevailing winds) and distinguish climate from weather.
A Regents answer on climate controls: the difference between weather and climate, how latitude, elevation, proximity to large bodies of water, ocean currents, mountain barriers (orographic effect and rain shadows) and prevailing winds set a region's temperature and precipitation, and why coastal and inland climates differ, with worked exam questions.
Sources & how we know this
- Earth and Space Sciences — New York State Education Department (2026)
- Regents Examination in Physical Setting/Earth Science — New York State Education Department (2026)