Question map
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?
Explanation
All three statements are correct.
**Statement I is correct:** In the absence of naturally occurring greenhouse effect, the average temperature of the earth surface would be -19°C instead of present value of 15°C and the earth would be a frozen lifeless planet.[1] Without greenhouse gases, the surface temperature of the planet would be about –19°C, and the Earth could not support life.[2] This demonstrates that temperatures would indeed be well below freezing everywhere without the atmosphere.
**Statement II is correct:** The greenhouse effect is a naturally occurring phenomenon that blankets the earth's lower atmosphere and warms it, maintaining the temperature suitable for living things to survive.[1] Greenhouse gases in the atmosphere absorb much of the infrared energy 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.[3]
**Statement III is correct:** 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.[4]
Sources- [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > 17.2. GREENHOUSE EFFECT > p. 254
- [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Greenhouse Effect and Global Warming > p. 7
- [3] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > Role of Greenhouse Gases > p. 255
- [4] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > Gases > p. 64
PROVENANCE & STUDY PATTERN
Full viewThis is a classic 'First Principles' question bridging Physical Geography and Environment. It rewards conceptual clarity over rote memorization. If you understood the *physics* of the Heat Budget in NCERT Class XI, this was a free hit. Do not skip the introductory 'mechanism' paragraphs in standard texts.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
- Statement 1: Would Earth's surface temperatures be well below the freezing point everywhere on the planet if Earth had no atmosphere?
- Statement 2: Does heat absorbed and trapped by Earth's atmosphere (the greenhouse effect) maintain the planet's average surface temperature?
- Statement 3: Are atmospheric gases such as carbon dioxide particularly effective at absorbing and trapping Earth's outgoing infrared radiation?
- Gives a real example of a body with no atmosphere (the Moon) and reports its average surface temperature is below freezing.
- Supports the idea that a surface without an atmosphere can have a mean temperature well below 0°C.
- Quantifies the effect of removing a major greenhouse gas (CO2) on Earth's surface temperature: a drop of approximately 33°C.
- Together with Earth's current average (given in other passages), a ~33°C drop implies mean temperatures would fall well below the freezing point.
- States Earth's natural greenhouse effect maintains an average temperature of 15 °C (59 °F).
- Provides the baseline temperature which, when reduced by the ~33°C collapse noted above, indicates averages below freezing.
States that the atmosphere keeps surface temperature within certain limits and that in its absence extremes of temperature would exist between day and night.
A student could combine this with the idea of day–night radiative heating to infer that, without an atmosphere, nights could become much colder (possibly below freezing) while days could be much hotter.
Explains the planetary heat budget and that some incoming solar energy is reflected/absorbed by the atmosphere before reaching the surface.
One could extend this by estimating the surface energy that would remain without atmospheric reflection/absorption to judge how much solar heating the bare surface would receive and whether average temperatures might remain above or fall below freezing.
Notes that a moderate temperature on Earth arises partly because the planet is the right size to support an atmosphere, which plays a major role in sustaining life.
A student could infer that losing the atmosphere would remove that moderating influence and then compare Earth’s solar input (using a basic Sun–Earth distance map) to evaluate likely surface temperatures without atmospheric effects.
Provides examples of planets with listed average temperatures and whether they have atmospheres, implying a connection between atmosphere presence and planetary surface temperature.
By comparing the table’s temperatures and atmosphere presence, a student could use planetary examples (and their distances from the Sun) to reason whether an airless Earth would resemble the temperature extremes of other airless or thin-atmosphere bodies.
Describes that the atmosphere causes temperature to decrease with altitude because the atmosphere is heated from the surface (normal lapse rate).
A student could use this rule to argue that, without an atmosphere heated from the surface, the vertical temperature structure would change and surface heat retention (especially at night) would be reduced, affecting whether surfaces stay above freezing.
- Explicitly describes the greenhouse effect as a natural phenomenon that blankets and warms the lower atmosphere.
- States this warming maintains temperatures suitable for life and gives the quantitative contrast (−19°C without vs 15°C with).
- Specifies that greenhouse gases allow Earth to maintain an average temperature of approximately 15°C.
- Directly asserts that without these gases the surface temperature would be about −19°C, linking the effect to habitability.
- Explains the physical mechanism: greenhouse gases absorb infrared emitted from the surface and re‑emit it, warming surface and lower atmosphere.
- Connects absorption/re‑emission to prevention of heat escape from Earth's system.
- Explicitly states carbon dioxide is transparent to incoming solar but opaque to outgoing terrestrial radiation.
- Says CO2 absorbs part of terrestrial radiation and reflects some back toward Earth's surface.
- Links this behavior directly to the greenhouse effect and surface warming.
- Says greenhouse gases absorb much of the infrared energy emitted from the Earth's surface.
- Describes re-emission in all directions that warms the surface and lower atmosphere.
- States long-wave (terrestrial) radiation is absorbed particularly by carbon dioxide and other greenhouse gases.
- Explains that this absorption heats the atmosphere from below and contributes to radiative exchange.
- [THE VERDICT]: Sitter. Directly sourced from NCERT Class XI (Fundamentals of Physical Geography, Ch 8) and Shankar IAS (Ch 17).
- [THE CONCEPTUAL TRIGGER]: The 'Heat Budget of the Earth' and the specific radiative properties of Greenhouse Gases (Shortwave transparency vs. Longwave opacity).
- [THE HORIZONTAL EXPANSION]: Memorize the Albedo sequence (Fresh Snow > Clouds > Sand > Forest); the Normal Lapse Rate (6.5°C/km); the specific wavelengths (Solar = Shortwave, Terrestrial = Longwave); and the fact that Water Vapor is actually the most abundant natural greenhouse gas, while CO2 is the primary anthropogenic driver.
- [THE STRATEGIC METACOGNITION]: Don't just study 'Global Warming' as a current affair. Study the *mechanism* of the Greenhouse Effect. Ask: 'Why does the atmosphere warm us?' The answer lies in the physics of radiation absorption, which solves all three statements.
The atmosphere moderates surface temperature and prevents extreme temperature swings between day and night.
High-yield for UPSC: explains why Earth is habitable and links to questions on planetary habitability, diurnal temperature range, and climate moderation. Mastering this helps answer comparative questions about planets and the effects of atmospheric loss.
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Temperature balance > p. 280
- Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 13: Our Home: Earth, a Unique Life Sustaining Planet > Did Mars ever support life? > p. 216
Surface temperature is set by the balance between incoming solar insolation and outgoing terrestrial radiation, with the atmosphere affecting how much energy reaches and leaves the surface.
Core concept for climate and geography questions: it underpins topics like albedo, greenhouse effect, and energy balance. Useful for framed questions on temperature change, warming, and why atmosphereless bodies behave differently.
- FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Heat Budget of the Planet Earth > p. 69
Temperature generally decreases with altitude in the troposphere, affecting how surface heating is transferred upward and shaping surface temperature patterns.
Valuable for meteorology and physical geography: explains mountain climates, troposphere structure, and temperature gradients. Enables answers on altitude effects, climate zones, and atmospheric layering.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Structure of the Atmosphere > p. 7
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > UPSC Prelims 2012] Normally, the temperature decreases with the increase in height from the Earth's surface, because > p. 295
The greenhouse effect keeps Earth's mean surface temperature high enough for liquid water and life, exemplified by the ~15°C versus −19°C contrast without greenhouse gases.
High-yield for questions on climate, habitability and human impacts; links to topics on water availability, biosphere limits and climate change policy. Enables answering why small changes in atmospheric composition can have large climate consequences.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 17: Climate Change > 17.2. GREENHOUSE EFFECT > p. 254
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Greenhouse Effect and Global Warming > p. 7
Greenhouse gases absorb outgoing longwave radiation and re‑emit it, which warms the Earth's surface and lower atmosphere.
Essential for mechanistic questions on radiative forcing, greenhouse gases, and mitigation measures; connects to chemistry of greenhouse gases and energy balance concepts used in climate policy and mitigation debates.
- 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 7: Climate Change > 2. greenhouse gases > p. 9
Earth's mean temperature is maintained when incoming solar radiation is balanced by outgoing terrestrial radiation; atmospheric absorption and reflection modify that balance.
Core for questions on Earth's energy balance, albedo, and climate feedbacks; helps integrate topics in physical geography, climatology and human impacts on radiative balance.
- FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > Heat Budget of the Planet Earth > p. 69
- Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 14: Climate > lnsolation > p. 131
Atmospheric gases like carbon dioxide transmit incoming shortwave solar radiation but absorb outgoing longwave terrestrial infrared, producing net warming.
High-yield for questions on Earth's radiative balance and the basic physics of the greenhouse effect; links to topics on surface temperature, energy budgets, and climate forcing. Mastery helps answer conceptual and policy questions about why certain gases matter more for warming.
- 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
The 'Atmospheric Window' (8–13 µm range) where the atmosphere is relatively transparent to terrestrial radiation, allowing some heat to escape. Also, the 'Inversion of Temperature' conditions (Long winter nights, clear skies, still air) which are the exact opposite of the conditions described in the Greenhouse Effect.
Use the 'Moon Analogy' for Statement I. The Moon is the same distance from the Sun but has no atmosphere; its night temperature drops to -173°C. This proves 'well below freezing.' For Statement III, apply the 'Crisis Logic': If CO2 wasn't good at trapping heat, the entire global warming narrative wouldn't exist. Thus, III must be true.
Links to GS-3 (Environment & Science): Understanding the Heat Budget is the foundation for explaining 'Urban Heat Islands' (concrete alters albedo/absorption) and 'Geo-engineering' proposals (like Stratospheric Aerosol Injection) which aim to artificially modify this radiative balance.