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Q53 (IAS/2014) Environment & Ecology › Climate Change & Global Initiatives › Climate science and impacts Official Key

The scientific view is that the increase in global temperature should not exceed 2 ℃ above pre-industrial level. If the global temperature increases beyond 3 ℃ above the pre-industrial level, what can be its possible impact/impacts on the world? 1. Terrestrial biosphere tends toward a net carbon source. 2. Widespread coral mortality will occur. 3. All the global wetlands will permanently disappear. 4. Cultivation of cereals will not be possible anywhere in the world. Select the correct answer using the code given below.

Result
Your answer: —  ·  Correct: B
Explanation

The correct answer is option B (statements 1 and 2 only).

The documents reference warming scenarios of approximately 3.5°C and 2.7°C above pre-industrial levels[2], indicating that temperature increases beyond 3°C are within the range of climate projections being studied. At such elevated temperatures, the terrestrial biosphere would likely shift toward being a net carbon source as vegetation and soils begin releasing more carbon than they absorb, creating a dangerous feedback loop (statement 1 is correct). Similarly, widespread coral mortality would occur at temperatures exceeding 3°C, as corals are extremely sensitive to temperature changes and experience mass bleaching events even at lower warming levels (statement 2 is correct).

However, statements 3 and 4 are extreme exaggerations. While many wetlands would face severe stress and some might disappear, claiming that ALL global wetlands will permanently disappear is not supported by scientific evidence. Similarly, while cereal cultivation would face significant challenges and yields would decline in many regions, stating that cultivation would be impossible "anywhere in the world" is unrealistic. Some regions, particularly in higher latitudes, might even see extended growing seasons. These absolute statements make options C and D incorrect.

Sources
  1. [1] https://www.worldbank.org/content/dam/Worldbank/document/Full_Report_Vol_2_Turn_Down_The_Heat_%20Climate_Extremes_Regional_Impacts_Case_for_Resilience_Print%20version_FINAL.pdf
  2. [2] https://www.worldbank.org/content/dam/Worldbank/document/Full_Report_Vol_2_Turn_Down_The_Heat_%20Climate_Extremes_Regional_Impacts_Case_for_Resilience_Print%20version_FINAL.pdf
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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. The scientific view is that the increase in global temperature should not exceed 2 ℃ above pre-industrial level. If the global temperatur…
At a glance
Origin: Mostly Current Affairs Fairness: Low / Borderline fairness Books / CA: 0/10 · 2.5/10
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This question is the ultimate 'Bark vs. Bite' example. While Statement 1 requires deep knowledge of IPCC carbon cycle feedbacks (often found in World Bank 'Turn Down the Heat' reports), Statements 3 and 4 are logically absurd extremes. You solve this by rejecting the impossible ('All', 'Anywhere'), not by knowing the obscure science.

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
If global mean temperature increases beyond 3°C above pre-industrial levels, does the terrestrial biosphere tend toward a net carbon source?
Origin: Weak / unclear Fairness: Borderline / guessy
Indirect textbook clues
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
“Higher temperatures and less rainfall in some areas may decrease soil moisture levels and actually suppress growth and agricultural yields. In addition to these, the ecologists and bio-geographers have predicted that as global temperature increases, the animal and plant species will shift towards the poles and to higher elevations to maintain their preferred temperature conditions.”
Why relevant

States that higher temperatures and reduced rainfall can decrease soil moisture, suppress plant growth and agricultural yields — a rule linking warming to reduced terrestrial productivity.

How to extend

A student could combine this with the basic idea that lower plant growth reduces ecosystem carbon uptake to infer that strong warming might weaken the land carbon sink and possibly turn it into a source.

Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 7: Climate Change > 2. greenhouse gases > p. 11
Strength: 4/5
“it will lead to catastrophic global warming, which would melt the polar ice-caps, resulting into sea-level rise, stormy weather, droughts and foods, which may be catastrophic to agriculture and other primary, secondary and tertiary activities. Since the beginning of the Industrial Revolution in Britain and Europe (1779), apart from the atmospheric concentration of carbon dioxide, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15 per cent. Te enhancement in temperature has, consequently, increased the temperature trapping capability of the Earth's atmosphere (Fig. 7.4). • (ii) Methane and Global Warming: Another radiative active gas contributing to the overall greenhouse efect is methane (CH4), which is increasing in concentration at about 1 per cent per year.”
Why relevant

Describes ‘catastrophic global warming’ impacts on agriculture and notes rising greenhouse gas concentrations (e.g., methane) — indicating stronger feedbacks and ecosystem stress under large warming.

How to extend

Using this pattern, a student could argue that more severe warming (≫2°C) increases ecosystem damage and greenhouse gas releases, which could shift net land carbon balance toward a source.

Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > z degreesCgoal > p. 428
Strength: 3/5
“A z degree Celsius rise in global temperatures from pre-industrial levels is the highest rise we can afford if we want a 50% chance of avoiding the worst effects of climate change. • The current concentration of carbon dioxide in the atmosphere is 370 parts per million. • The concentration of carbon dioxide equivalent in the atmosphere that the world must stay at or under to stay true to the z degrees Celsius goal is 450 parts per million. All Rights Reserved. No part of this material may be reproduced in any form or by any means, without permission in writing.”
Why relevant

Gives the concept of temperature thresholds (e.g., staying below specified °C increases to avoid worst effects), implying impacts escalate with larger temperature increases.

How to extend

A student could extend this threshold idea to reason that exceeding higher thresholds (such as 3°C) likely produces much larger biosphere impacts that could undermine terrestrial carbon uptake.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Carbon Dioxide > p. 272
Strength: 3/5
“• Being an efficient absorber of heat, carbon dioxide is a very important factor in the heat energy budget. With the increased burning of fossil fuels, the percentage of carbon dioxide in the atmosphere is increasing at an alarming rate. This could significantly raise the temperature at lower levels of the atmosphere.”
Why relevant

Explains that increased CO2 and warming arise from fossil-fuel burning and that CO2 strongly affects the heat budget — linking human emissions to rising temperatures that stress ecosystems.

How to extend

Combined with maps or emissions scenarios, a student could infer that continued emissions driving >3°C warming would amplify stressors on land biota, making a net source outcome more plausible.

Statement analysis

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Statement analysis

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Statement analysis

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