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Q1 (IAS/2024) Geography › World Physical Geography › Atmospheric heat balance Official Key

Consider the following statements : Statement-I : The atmosphere is heated more by incoming solar radiation than by terrestrial radiation. Statement-II : Carbon dioxide and other greenhouse gases in the atmosphere are good absorbers of long wave radiation. Which one of the following is correct in respect of the above statements ?

Result
Your answer:  ·  Correct: D
Explanation

The correct answer is option D because Statement-I is incorrect while Statement-II is correct.

The bulk of the incoming solar radiation is absorbed by the Earth's surface, not[1] by the atmosphere[2]. The atmosphere transmits the incoming solar radiation but absorbs the vast majority of long wave radiation emitted upwards by the earth's surface[3]. This means the atmosphere is heated MORE by terrestrial (longwave) radiation than by incoming solar radiation, making Statement-I incorrect.

Statement-II is correct because carbon dioxide is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation, and it absorbs a part of terrestrial radiation and reflects back some part of it towards the earth's surface[4]. Greenhouse gases in the atmosphere absorb much of the infrared energy emitted from the Earth's surface, preventing it from escaping, and then re-emit this energy in all directions, warming the Earth's surface and lower atmosphere[5].

Therefore, Statement-I is incorrect but Statement-II is correct, making option D the right answer.

Sources
  1. [1] https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg1-faqs-1.pdf
  2. [2] https://www.ipcc.ch/site/assets/uploads/2018/03/ipcc_far_wg_I_full_report.pdf
  3. [3] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Global Warming > p. 96
  4. [4] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > Gases > p. 64
  5. [5] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Role of Greenhouse Gases > p. 255
How others answered
Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.
Community Performance
Out of everyone who attempted this question.
57%
got it right
PROVENANCE & STUDY PATTERN
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Consider the following statements : Statement-I : The atmosphere is heated more by incoming solar radiation than by terrestrial radiati…
At a glance
Origin: Books + Current Affairs Fairness: Low / Borderline fairness Books / CA: 3.3/10 · 6.7/10

This is a classic 'First Principles' Geography question directly from NCERT Class XI. It tests the fundamental physics of the Greenhouse Effect (Shortwave In vs. Longwave Out). If you understand why temperature decreases with height (Lapse Rate), you know the heat source is the ground, not the sun directly.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Is Earth's atmosphere heated more by incoming solar (shortwave) radiation than by terrestrial (longwave) radiation?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"Outgoing Longwave Radiation 235 Wm−2 Incoming Solar Radiation 342 Wm−2 ... Absorbed by Atmosphere ... Back Radiation 390 Surface Radiation 350"
Why this source?
  • Provides an energy-budget style breakdown with magnitudes showing atmospheric absorption of solar vs. large longwave exchanges (e.g., back radiation).
  • Shows back radiation (~390 W/m2) and surface longwave fluxes are large compared with direct atmospheric solar absorption values in the same budget.
Web source
Presence: 5/5
"About half of the incoming solar radiation is absorbed by the Earth’s surface. This energy is transferred to the atmosphere by warming the air in contact with the surface (thermals), by ­evapotranspiration and by longwave radiation that is absorbed by clouds and greenhouse gases."
Why this source?
  • States that about half of incoming solar is absorbed by the surface rather than directly by the atmosphere.
  • Explains that the atmosphere is heated by energy transferred from the surface (thermals, evapotranspiration) and by longwave radiation absorbed by clouds and greenhouse gases.
Web source
Presence: 4/5
"The bulk of the incoming solar radiation is absorbed not by the atmosphere but by the Earth's surface (soil, ocean, ice)"
Why this source?
  • Explicitly states that the bulk of incoming solar radiation is absorbed by the Earth's surface, not the atmosphere.
  • Implies the atmosphere's heating is largely driven by surface-absorbed solar energy being redistributed rather than direct shortwave absorption by the atmosphere.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > The Passage of Solar Radiation through the Atmosphere > p. 68
Strength: 5/5
“The atmosphere is largely transparent to short wave solar radiation. The incoming solar radiation passes through the atmosphere before striking the earth's surface. Within the troposphere water vapour, ozone and other gases absorb much of the near infrared radiation. Very small-suspended particles in the troposphere scatter visible spectrum both to the space and towards the earth surface. This process adds colour to the sky. The red colour of the rising and the setting sun and the blue colour of the sky are the result of scattering of light within the atmosphere.”
Why relevant

States the atmosphere is largely transparent to incoming shortwave solar radiation, with most solar reaching the surface (some near‑IR/water vapour absorption and scattering occur).

How to extend

A student could combine this with the fact that if most shortwave reaches the surface, then direct atmospheric heating from shortwave is limited compared to surface absorption.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Terrestrial Radiation > p. 69
Strength: 5/5
“earth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in long wave form. This energy heats up the atmosphere from below. This process is known as terrestrial radiation. The long wave radiation is absorbed by the atmospheric gases particularly by carbon dioxide and the other green house gases. Thus, the atmosphere is indirectly heated by the earth's radiation. The atmosphere in turn radiates and transmits heat to the space. Finally the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth's surface and in the atmosphere.”
Why relevant

Explains that the warmed Earth radiates longwave energy upward and that this terrestrial longwave is absorbed by greenhouse gases, heating the atmosphere from below.

How to extend

Combine with estimates of surface emission (from surface temperature) to infer the magnitude of longwave energy available to heat the atmosphere.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > 22.2. Lapse Rate > p. 295
Strength: 4/5
“Hence, the lapse rate of the troposphere below tropopause is positive, the lapse rate of the tropopause is zero, and the lapse rate of the stratosphere is negative.• The fall in temperature with altitude is primarily due to the following reason: • Atmosphere is mostly transparent to the incoming shortwave radiation but actively absorbs the outgoing terrestrial (longwave) radiation.• Greenhouse house gases like CO2, and water vapour, are the primary absorbers of terrestrial radiation and their concentration is highest at the earth's surface and goes on decreasing with altitude. Hence, the temperature falls with altitude (elevation).• The lapse rate of non-rising air (environmental lapse rate) is highly variable, being affected by radiation, convection, condensation and concentration of greenhouse gases.”
Why relevant

Gives the general rule: atmosphere is mostly transparent to incoming shortwave but actively absorbs outgoing terrestrial longwave; links this to temperature lapse rate.

How to extend

Use this rule plus the vertical distribution of greenhouse gases (concentrated near surface) to argue that absorbed longwave dominates near‑surface atmospheric heating.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Global Warming > p. 96
Strength: 4/5
“Due to the presence of greenhouse gases, the atmosphere is behaving like a greenhouse. The atmosphere also transmits the incoming solar radiation but absorbs the vast majority of long wave radiation emitted upwards by the earth's surface. The gases that absorb long wave radiation are called greenhouse gases. The processes that warm the atmosphere are often collectively referred to as the greenhouse effect. The term greenhouse is derived from the analogy to a greenhouse used in cold areas for preserving heat. A greenhouse is made up of glass. The glass which is transparent to incoming short wave solar radiation is opaque to outgoing long wave radiation.”
Why relevant

Summarises the greenhouse effect: atmosphere transmits incoming solar but absorbs the vast majority of longwave emitted by the surface.

How to extend

A student could take this qualitative ‘vast majority’ claim and compare it to known solar fluxes (insolation) to judge which flux heats the atmosphere more.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Structure of the Atmosphere > p. 8
Strength: 3/5
“Te upper boundary of this layer is called the mesopause.• 4. Termosphere (Heat Sphere): Tis sphere extends from 80 to 480 kms in altitude. In thermosphere, temperatures increase with height. High temperatures are generated in the thermosphere because the gas molecules absorb shortwave solar radiation. Te temperature curve in Fig. 1.2 shows that temperature rises sharply in the thermosphere, up to 1200°C and higher. Despite such high temperatures, the thermosphere is not 'hot' in the way one might expect. Temperature and heat are two diferent things. Te intense solar radiation in this portion of the atmosphere excites individual molecules and atoms (principally nitrogen and oxygen).”
Why relevant

Shows an important exception: high-altitude thermosphere absorbs shortwave solar radiation strongly, producing high temperatures aloft.

How to extend

Combine this with knowledge of atmospheric mass/energy distribution to note that shortwave heating can dominate in upper layers while longwave heating dominates the lower atmosphere.

Statement 2
Do carbon dioxide and other greenhouse gases in Earth's atmosphere strongly absorb longwave (thermal infrared) radiation?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Role of Greenhouse Gases > p. 255
Presence: 5/5
“o Greenhouse gases in the atmosphere absorb much of the infrared energy (infrared radiation) emitted from the Earth's surface, preventing it from escaping from the Earth's system. The greenhouse gases then re-emit this energy in all directions, warming the Earth's surface and lower atmosphere.”
Why this source?
  • Explicitly says greenhouse gases absorb much of the infrared energy emitted from Earth's surface.
  • Notes that these gases re-emit energy in all directions, causing warming of surface and lower atmosphere.
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Global Warming > p. 96
Presence: 5/5
“Due to the presence of greenhouse gases, the atmosphere is behaving like a greenhouse. The atmosphere also transmits the incoming solar radiation but absorbs the vast majority of long wave radiation emitted upwards by the earth's surface. The gases that absorb long wave radiation are called greenhouse gases. The processes that warm the atmosphere are often collectively referred to as the greenhouse effect. The term greenhouse is derived from the analogy to a greenhouse used in cold areas for preserving heat. A greenhouse is made up of glass. The glass which is transparent to incoming short wave solar radiation is opaque to outgoing long wave radiation.”
Why this source?
  • States the atmosphere absorbs the vast majority of longwave radiation emitted upward by the surface.
  • Defines gases that absorb longwave radiation as greenhouse gases, linking absorption to the greenhouse effect.
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > Gases > p. 64
Presence: 5/5
“Carbon dioxide is meteorologically a very important gas as it is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation. It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth's surface. It is largely responsible for the green house effect. The volume of other gases is constant but the volume of carbon dioxide has been rising in the past few decades mainly because of the burning of fossil fuels. This has also increased the temperature of the air. Ozone is another important component of the atmosphere found between 10 and 50 km above the earth's surface and acts as a filter and absorbs the ultra-violet rays radiating from the sun and prevents them from reaching the surface of the earth.”
Why this source?
  • Specifically describes carbon dioxide as transparent to incoming solar but opaque to outgoing terrestrial (longwave) radiation.
  • Says CO2 absorbs part of terrestrial radiation and reflects some back toward the surface, implicating strong longwave absorption.
Statement 3
Does absorption of longwave radiation by carbon dioxide and other greenhouse gases explain why Earth's atmosphere is heated more by incoming solar radiation than by terrestrial radiation?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 4/5
"This energy is transferred to the atmosphere by warming the air in contact with the surface (thermals), by ­evapotranspiration and by longwave radiation that is absorbed by clouds and greenhouse gases."
Why this source?
  • States how energy from the surface is transferred to the atmosphere, explicitly including longwave radiation absorbed by clouds and greenhouse gases.
  • Shows that longwave absorption by greenhouse gases is a direct pathway for heating the atmosphere (i.e., atmosphere gains energy from surface-emitted longwave).
Web source
Presence: 5/5
"The atmosphere is relatively transparent to solar radiation, but it is nearly opaque to longwave radiation. The atmosphere typically absorbs most of the longwave radiation emitted by the surface."
Why this source?
  • Directly states the atmosphere is relatively transparent to solar but nearly opaque to longwave radiation, linking greenhouse gases to strong longwave absorption.
  • Adds that the atmosphere typically absorbs most longwave radiation emitted by the surface, implying significant atmospheric heating from terrestrial (longwave) radiation.
Web source
Presence: 4/5
"Incoming Solar Radiation 342 Wm−2 Absorbed by Atmosphere 67 Back Radiation 390 Surface Radiation 350"
Why this source?
  • Provides quantitative energy-flow figures showing how much solar is incident and how much is absorbed by the atmosphere, allowing comparison between direct solar absorption and longwave exchanges.
  • Includes large values for surface and back radiation, illustrating the substantial longwave fluxes exchanged between surface and atmosphere.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Terrestrial Radiation > p. 69
Strength: 4/5
“earth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in long wave form. This energy heats up the atmosphere from below. This process is known as terrestrial radiation. The long wave radiation is absorbed by the atmospheric gases particularly by carbon dioxide and the other green house gases. Thus, the atmosphere is indirectly heated by the earth's radiation. The atmosphere in turn radiates and transmits heat to the space. Finally the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth's surface and in the atmosphere.”
Why relevant

States that the Earth radiates longwave energy which is absorbed by CO2 and other greenhouse gases, meaning the atmosphere is heated indirectly from terrestrial radiation.

How to extend

A student could combine this with the basic fact that most solar energy reaches and heats the surface (shortwave passes through) to compare the relative roles of incoming solar vs. outgoing terrestrial heating of the atmosphere.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Global Warming > p. 96
Strength: 5/5
“Due to the presence of greenhouse gases, the atmosphere is behaving like a greenhouse. The atmosphere also transmits the incoming solar radiation but absorbs the vast majority of long wave radiation emitted upwards by the earth's surface. The gases that absorb long wave radiation are called greenhouse gases. The processes that warm the atmosphere are often collectively referred to as the greenhouse effect. The term greenhouse is derived from the analogy to a greenhouse used in cold areas for preserving heat. A greenhouse is made up of glass. The glass which is transparent to incoming short wave solar radiation is opaque to outgoing long wave radiation.”
Why relevant

Explains the general rule that the atmosphere is largely transparent to shortwave solar radiation but absorbs most longwave radiation emitted by the surface (the greenhouse effect).

How to extend

Use a world-map or energy-balance numbers to estimate how much energy arrives as shortwave at the surface vs. how much is re-emitted as longwave and then absorbed to judge which process supplies more atmospheric heating.

FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > Gases > p. 64
Strength: 4/5
“Carbon dioxide is meteorologically a very important gas as it is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation. It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth's surface. It is largely responsible for the green house effect. The volume of other gases is constant but the volume of carbon dioxide has been rising in the past few decades mainly because of the burning of fossil fuels. This has also increased the temperature of the air. Ozone is another important component of the atmosphere found between 10 and 50 km above the earth's surface and acts as a filter and absorbs the ultra-violet rays radiating from the sun and prevents them from reaching the surface of the earth.”
Why relevant

Gives an explicit example: CO2 is transparent to incoming solar but opaque to outgoing terrestrial radiation and reflects some back to the surface — highlighting the differing interaction with shortwave vs. longwave.

How to extend

A student could apply this pattern to infer vertical heating profiles (surface-heated then atmosphere heated by upwelling longwave) and compare that with direct solar heating of atmospheric layers.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Greenhouse Effect and Global Warming > p. 7
Strength: 5/5
“Te process whereby radiatively active gases absorb and delay the loss of heat to space, thus keeping the lower troposphere moderately warmed through the radiation and eradication of infrared wavelengths. In other words, the greenhouse efect is a natural phenomenon that occurs when short-wave solar radiation from the Sun passes largely through the Earth's atmosphere, is absorbed at the planetary surface, is reradiated upward as long-wavelength thermal radiation, and is absorbed by various atmospheric constituents and again reradiated. Since some of this latter radiation fux is directed downward, it results in a surface warming that would not occur in the absence of an atmosphere.”
Why relevant

Describes the mechanism that radiatively active gases absorb outgoing longwave, re-emit it (some downward), and thus keep the lower troposphere warmed.

How to extend

Combine this process description with basic quantitative solar flux values (solar constant, surface absorption) to assess whether the absorbed/re-emitted longwave can account for greater atmospheric heating than direct solar absorption.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > 22.2. Lapse Rate > p. 295
Strength: 4/5
“Hence, the lapse rate of the troposphere below tropopause is positive, the lapse rate of the tropopause is zero, and the lapse rate of the stratosphere is negative.• The fall in temperature with altitude is primarily due to the following reason: • Atmosphere is mostly transparent to the incoming shortwave radiation but actively absorbs the outgoing terrestrial (longwave) radiation.• Greenhouse house gases like CO2, and water vapour, are the primary absorbers of terrestrial radiation and their concentration is highest at the earth's surface and goes on decreasing with altitude. Hence, the temperature falls with altitude (elevation).• The lapse rate of non-rising air (environmental lapse rate) is highly variable, being affected by radiation, convection, condensation and concentration of greenhouse gases.”
Why relevant

Links the atmospheric lapse rate (temperature decrease with altitude) to the pattern that the atmosphere is transparent to incoming shortwave but actively absorbs outgoing longwave; greenhouse gases concentration near the surface affects heating.

How to extend

Use the lapse-rate implication and knowledge of greenhouse gas vertical distribution to reason whether atmospheric heating is dominated by surface-emitted longwave absorption versus direct solar heating aloft.

Pattern takeaway: UPSC is prioritizing 'Process-based' questions over 'Fact-based' ones in Physical Geography. They want to know if you understand the *physics* of the atmosphere, not just the environmental consequences like Global Warming.
How you should have studied
  1. [THE VERDICT]: Sitter. Directly solvable from NCERT Class XI (Fundamentals of Physical Geography), Chapter 8: Solar Radiation, Heat Balance and Temperature.
  2. [THE CONCEPTUAL TRIGGER]: The 'Heat Budget' of the Earth. Specifically, the distinction between 'Insolation' (Shortwave) and 'Terrestrial Radiation' (Longwave).
  3. [THE HORIZONTAL EXPANSION]: Memorize the Heat Budget breakdown: 35 units reflected (Albedo), 14 units absorbed by atmosphere (Solar), 51 units absorbed by Earth. Key Albedo sequence: Fresh Snow (80-90%) > Clouds > Sand > Forest > Ocean. Understand 'Normal Lapse Rate' (6.5°C/km) vs 'Adiabatic Lapse Rate'.
  4. [THE STRATEGIC METACOGNITION]: Do not just memorize 'CO2 causes warming'. Ask 'How?'. The mechanism (transparency to shortwave, opacity to longwave) is the core examinable fact. Always link physical phenomena (Lapse Rate) to their cause (Ground-based heating).
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Greenhouse effect: atmosphere heated by terrestrial (longwave) radiation
💡 The insight

Greenhouse gases absorb outgoing longwave infrared from the warmed surface, producing most atmospheric heating rather than direct shortwave absorption.

High-yield for questions on climate, radiative forcing and global warming; links radiative transfer to surface–atmosphere coupling and policy debates on greenhouse gas emissions. Mastery enables explanation of atmospheric warming mechanisms, temperature profiles, and impacts of CO2 and water vapour changes.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Global Warming > p. 96
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Terrestrial Radiation > p. 69
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > 22.2. Lapse Rate > p. 295
🔗 Anchor: "Is Earth's atmosphere heated more by incoming solar (shortwave) radiation than b..."
📌 Adjacent topic to master
S1
👉 Atmospheric transparency to incoming shortwave radiation
💡 The insight

The atmosphere is largely transparent to solar shortwave, so most solar energy reaches and heats the surface rather than directly heating the air.

Essential for understanding surface heating, diurnal temperature range, and the role of clouds/albedo; helps answer questions contrasting surface vs atmospheric energy uptake and interpreting observational radiation budgets.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > The Passage of Solar Radiation through the Atmosphere > p. 68
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > SOLAR RADIATION > p. 67
  • Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 14: Climate > lnsolation > p. 131
🔗 Anchor: "Is Earth's atmosphere heated more by incoming solar (shortwave) radiation than b..."
📌 Adjacent topic to master
S1
👉 Planetary heat budget: insolation in, terrestrial radiation out
💡 The insight

Earth maintains energy balance by receiving shortwave insolation and returning energy as longwave terrestrial radiation, which is central to how heat is distributed between surface and atmosphere.

Core concept for physical geography and climate sections; useful for solving energy-balance problems, explaining feedbacks (clouds, albedo), and framing questions on temperature equilibrium and climate change.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > 21.5. Heat Budget > p. 293
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Emission > p. 255
🔗 Anchor: "Is Earth's atmosphere heated more by incoming solar (shortwave) radiation than b..."
📌 Adjacent topic to master
S2
👉 Greenhouse gases = longwave (infrared) absorbers
💡 The insight

Greenhouse gases are defined by their ability to absorb outgoing longwave (thermal infrared) radiation and thereby trap heat.

High-yield for questions on radiative forcing and climate: it links atmospheric composition to surface warming and helps explain why changes in gas concentrations alter Earth’s energy balance. Mastering this aids answers on greenhouse effect mechanics, climate drivers, and mitigation rationale.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Role of Greenhouse Gases > p. 255
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Global Warming > p. 96
🔗 Anchor: "Do carbon dioxide and other greenhouse gases in Earth's atmosphere strongly abso..."
📌 Adjacent topic to master
S2
👉 Carbon dioxide: shortwave transparent, longwave opaque
💡 The insight

Carbon dioxide transmits incoming solar shortwave radiation but absorbs and re-emits outgoing terrestrial longwave radiation.

Crucial for explaining CO2’s specific role in warming, trends in atmospheric CO2, and policy debates about fossil fuel emissions; connects to topics on radiative properties, energy balance, and anthropogenic climate change questions.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > Gases > p. 64
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 7: Climate Change > 2. greenhouse gases > p. 9
🔗 Anchor: "Do carbon dioxide and other greenhouse gases in Earth's atmosphere strongly abso..."
📌 Adjacent topic to master
S2
👉 Absorption and re-emission drives atmospheric heating
💡 The insight

Absorbed longwave radiation is re-emitted by gases in all directions, including back toward the surface, warming the lower atmosphere.

Useful for explaining temperature profiles, the mechanism of the greenhouse effect, and the distinction between solar heating and terrestrial re-radiation; equips aspirants to answer process-based questions on climate dynamics and feedbacks.

📚 Reading List :
  • Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Role of Greenhouse Gases > p. 255
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Greenhouse Effect and Global Warming > p. 7
🔗 Anchor: "Do carbon dioxide and other greenhouse gases in Earth's atmosphere strongly abso..."
📌 Adjacent topic to master
S3
👉 Greenhouse effect: shortwave in, longwave trapped
💡 The insight

The atmosphere is largely transparent to incoming shortwave solar radiation but absorbs outgoing longwave terrestrial radiation, which controls how the atmosphere is warmed.

High-yield for UPSC because it is central to questions on Earth's energy balance, climate change and the greenhouse mechanism. Links physical geography to environmental science and policy topics (radiative balance, global warming). Enables tackling questions on why surface and lower atmosphere temperatures differ from a no-atmosphere case and on effects of changing greenhouse gas concentrations.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Global Warming > p. 96
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > The Passage of Solar Radiation through the Atmosphere > p. 68
🔗 Anchor: "Does absorption of longwave radiation by carbon dioxide and other greenhouse gas..."
🌑 The Hidden Trap

The 'Atmospheric Window' (8–14 µm). While CO2 absorbs longwave, there is a specific spectral window where the atmosphere is transparent to outgoing terrestrial radiation, allowing heat to escape. Clouds close this window, which is why cloudy nights are warmer.

⚡ Elimination Cheat Code

Use the 'Mountain Top Logic'. If the atmosphere were heated primarily by incoming solar radiation (from above), the upper layers (mountains) would be warmer than the plains. Since mountains are colder, the heat source must be from *below* (the ground/terrestrial radiation). Thus, Statement I is physically impossible given the existence of the Lapse Rate.

🔗 Mains Connection

Link this to Environment (Climate Change): The concept of 'Global Warming Potential' (GWP) is based on this radiative efficiency. CO2 is the baseline (GWP=1). Methane absorbs longwave 25-30x more effectively. SF6 is ~23,500x. This physics dictates the Kyoto/Paris baskets.

✓ Thank you! We'll review this.

SIMILAR QUESTIONS

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Consider the following statements : Statement-I : The temperature contrast between continents and oceans is greater during summer than in winter. Statement-II : The specific heat of water is more than that of land surface. Which one of the following is correct in respect of the above statements?

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Consider the following statements : Statement I : The amount of dust particles in the atmosphere is more in subtropical and temperate areas than in equatorial and polar regions. Statement II : Subtropical and temperate areas have less dry winds. Which one of the following is correct in respect of the above statements?

IAS · 2025 · Q29 Relevance score: 3.22

Consider the following statements : I. Without the atmosphere, temperature would be well below freezing point everywhere on the Earth's surface. II. Heat absorbed and trapped by the atmosphere maintains our planet's average temperature. III. Atmosphere's gases, like carbon dioxide, are particularly good at absorbing and trapping radiation. Which of the statements given above are correct?

IAS · 2025 · Q33 Relevance score: 3.01

Consider the following statements : Statement I : Scientific studies suggest that a shift is taking place in the Earth's rotation and axis. Statement II : Solar flares and associated coronal mass ejections bombarded the Earth's outermost atmosphere with tremendous amount of energy. Statement III : As the Earth's polar ice melts, the water tends to move towards the equator. Which one of the following is correct in respect of the above statements?