UPSC Prelims 2014 Question:

The scientific view is that the increase in global temperature should not exceed 2° Celsius 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?

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:

Explanation:

• The terrestrial biosphere can release or absorb greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), and therefore has an important role in regulating atmospheric composition and climate. More greenhouse gas emissions will lead to more climate extremes and widespread damaging effects across our planet. Due to this, the terrestrial biosphere tends towards a net carbon source. So, point 1 is correct.
  
  
• A rampant decrease (and not permanent disappearance) in the number of wetlands could be one possible outcome of climate change and a high impact on aquatic biodiversity could be seen. Increased temperature can also lead to high-intensity of coral mortality across various regions of the world as they can survive only in limited range temperature range. So, point 2 is correct and point 3 is not correct.
  
  
• Increased global temperature will also widely impact the agriculture sector in a way that might reduce the productivity of land to cultivate certain crops. Although it might affect the production of cereals, it cannot be said that its cultivation will not be possible anywhere in the world. So, point 4 is not correct.
  
  

Therefore, option (2) is the correct answer. 

Subject: Environment | Climate change