The scientific view is that the increase in global temperature should not exceed 2 °C above 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?
- Terrestrial biosphere tends toward a net carbon source
- Widespread coral mortality will occur.
- All the global wetlands will permanently disappear.
- Cultivation of cereals will not be possible anywhere in the world.
Select the correct answer using the code given below.
- 1 only
- 1 and 2 only
- 2, 3 and 4 only
- 1, 2, 3 and 4
Explanation
Statement 1 is correct
- With temperature rise beyond ~3°C, the terrestrial biosphere (forests, soils, vegetation) may shift from being a carbon sink to a carbon source due to increased respiration, forest dieback, and wildfires. This accelerates global warming through positive feedback.
Statement 2is correct
- At >3°C warming, widespread coral mortality is highly likely due to severe and frequent marine heatwaves, leading to mass coral bleaching and ecosystem collapse.
Statement 3 is incorrect
- It is too extreme to say all global wetlands will permanently disappear. While many wetlands may degrade or shrink due to sea-level rise and altered hydrology, complete global disappearance is not supported scientifically.
Statement 4 is incorrect
- Even under severe warming, cultivation of cereals will not completely stop worldwide. Agricultural zones may shift geographically, and yields may decline in many regions, but total global impossibility is unrealistic
