Question 40 from UPSC CSE 2014 - Environme nt

Question

The scientific view is that the increase in global temperature should not exceed 2Â°C above pre-industrial level. If the global temperature increases beyond 3Â°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:

IASCODEX · Accepted Answer

Correct Option: B. 1 and 2 only

Strategy: Evaluate each statement for extremity and plausibility. Statements 3 and 4 use absolute terms like 'all' and 'anywhere,' which are highly improbable even under severe warming—so they're excluded. Statements 1 and 2 align with climate science: terrestrial ecosystems could shift from sink to source as warming intensifies, and coral reefs are extremely heat-sensitive, so mass mortality is very likely beyond 3°C. Thus, select option B.

Key Info: - **Global temperature targets:** are aimed at limiting warming to 1.5–2°C above pre-industrial levels, per the Paris Agreement, to avoid catastrophic impacts.
- **Terrestrial biosphere:** Forests, soils, and other land ecosystems currently act as carbon sinks, absorbing more CO2 than they emit. However, at higher warming (>3°C), increased ecosystem respiration, reduced productivity, soil carbon losses, and disturbances like fires or pest outbreaks can cause some regions to emit more carbon than they absorb, making them carbon sources.
- **Coral reefs:** Highly sensitive to temperature rise, widespread coral bleaching and mortality occur when ocean temperatures increase. Beyond 2°C, almost all warm-water reef-forming corals risk extinction, according to the Intergovernmental Panel on Climate Change (IPCC) Special Reports.
- **Wetlands:** While many wetlands are threatened by climate change-induced sea level rise and droughts, not all would 'permanently disappear' even in severe scenarios. Projected losses are serious but not absolute.
- **Cereal cultivation:** Production is highly vulnerable to higher average temperatures, droughts, and extreme events. However, adaptation by shifting crops, developing climate-resistant varieties, or regional differences would prevent total cessation of cereal cultivation everywhere.
- **Major references:** include IPCC Assessment Reports (AR5/AR6), peer-reviewed climate science, and the Paris Climate Agreement.

IASCODEX · Answer

Option A: 1 only

IASCODEX · Answer

Option C: 2, 3, and 4 only

IASCODEX · Answer

Option D: 1, 2, 3, and 4