UPSC Prelims 2014 Q53: Environment & Ecology – Climate Change & Greenhouse Gases
The scientific view is that the increase in global temperature should not exceed 2 °C above
the pre - industrial level. If the global temperature increases beyond 3 °C 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.
- (a) 1 only
- (b) 1 and 2 only
- (c) 2, 3 and 4 only
- (d) 1, 2, 3 and 4
Answer: (b) 1 and 2 only
Explanation
Impacts of warming beyond 3 °C
| Statement | Verdict | Reason |
|---|---|---|
| 1. Terrestrial biosphere tends toward a net carbon source | Correct | Forests die back, soils and permafrost release carbon |
| 2. Widespread coral mortality will occur | Correct | Warm, more acidic seas cause bleaching and death |
| 3. All the global wetlands will permanently disappear | Incorrect | Many will be damaged, but 'all' and 'permanently' go too far |
| 4. Cultivation of cereals will not be possible anywhere in the world | Incorrect | Yields fall in the tropics, but farming continues, and 'anywhere' is extreme |
Temperature goals:
| Level | Meaning |
|---|---|
| 2 °C | Upper limit accepted at Copenhagen (2009) and Paris (2015) |
| 1.5 °C | The safer goal countries will pursue under the Paris Agreement |
These findings come from the IPCC assessment reports.
Answer: (b) 1 and 2 only.
Why each option is right or wrong
- (a) Incorrect. Statement 2 is also true: widespread coral mortality will occur.
- (b) CORRECT. The land becomes a net carbon source, and corals die widely.
- (c) Incorrect. Statements 3 and 4 are extreme and false.
- (d) Incorrect. 'All wetlands' and 'anywhere in the world' are overstatements.
Key point
Beyond 3 °C: land turns from carbon sink to source; widespread coral death; not the loss of all wetlands or all cereal farming. Goals: 2 °C and 1.5 °C.
Remember
Above 3 °C: land emits carbon, corals die.
Common mistakes
- Accepting absolute words: 'all', 'permanently', 'anywhere'.
- Not knowing that forests can become a carbon source.
- Confusing the 2 °C limit with the 1.5 °C aspiration.
Exam tip
In climate-impact questions, reject the doomsday absolutes. Severe is likely; total is not.
Sources
- Intergovernmental Panel on Climate Change — Fourth and Fifth Assessment Reports (Impacts, Adaptation and Vulnerability)
- UNFCCC — The Paris Agreement