📘 IAS Prelims 2025 — GS-III Q.64 | Classroom Explanation

(Wet-Bulb Temperature | Climate Risk | Human & Ecological Survival)

📌 Question Recap

The World Bank warned that India could become one of the first places where wet-bulb temperatures routinely exceed 35°C.

Which of the following statements best reflect(s) the implication of the above report?

I. Peninsular India will most likely suffer from flooding, tropical cyclones and droughts.
II. The survival of animals including humans will be affected as shedding of their body heat through perspiration becomes difficult.

✅ Correct Answer: (c)

Both I and II

🧑‍🏫 Core Explanation (Concept + Application)

🔹 Understanding Wet-Bulb Temperature (FOUNDATIONAL)

• Wet-bulb temperature combines:
  • Heat (temperature) + Humidity
• At 35°C wet-bulb, the human body cannot cool itself, even in shade, with unlimited water and airflow.

📌 This is considered the upper survivability threshold for humans and most mammals.

🔹 Statement II ✅ Correct (Direct & Critical Impact)

• Humans and animals cool their bodies mainly through evaporation of sweat.
• When air is already saturated with moisture, sweat cannot evaporate.
• Result:
  • Core body temperature rises uncontrollably
  • Leads to heat exhaustion, heat stroke, organ failure, and death

📌 This is the most direct and scientifically established implication of wet-bulb temperatures crossing 35°C.

✔ Hence, Statement II is correct.

🔹 Statement I ✅ Correct (Broader Climate Consequences)

The same climate processes that push wet-bulb temperatures upward also cause:

• More intense monsoonal rainfall → Flooding
• Warmer oceans → Stronger tropical cyclones
• Erratic rainfall patterns → Longer dry spells and droughts

📌 Peninsular India is especially vulnerable because:

• Long coastline
• High humidity
• Dense population
• Urban heat-island effects

✔ Hence, Statement I is also correct.

🌍 High-Value Enrichment Points (Prelims Gold)

🔸 1. Why India is at Exceptional Risk

• Tropical latitude
• High population density
• Coastal humidity
• Urbanisation + deforestation
• Dependence on monsoon rainfall

🔸 2. Animals at Risk (Often Ignored)

• Livestock deaths during heat waves
• Reduced milk yield and fertility
• Collapse of outdoor labour systems
• Impact on wildlife unable to migrate fast enough

🔸 3. Difference Between Heat Index & Wet-Bulb (UPSC Trap)

👉 Wet-bulb is far more dangerous.

🔸 4. Policy Relevance (India)

• Drives need for:
  • Heat Action Plans
  • Climate-resilient infrastructure
  • Urban cooling strategies
  • Early warning systems
• Strong linkage with SDG-13 (Climate Action)

🎯 Final Answer Recap

• ✅ Statement I — Correct
• ✅ Statement II — Correct

✅ Correct Answer: (c)

Both I and II