Question

At present concentration of $\text{CO}_2$ in the atmosphere is about ____}

• A. 280 ppm
• B. 400 ppm
• C. 300 ppm
• D. 290 ppm

Hint:

Remember the benchmark figures: Pre-industrial \(\text{CO}_2 \approx 280\text{ ppm}\), while modern-day \(\text{CO}_2\) has surpassed the \( 400\text{ ppm}\) mark.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Carbon dioxide (\(\text{CO}_2\)) is a key greenhouse gas in the Earth's atmosphere.
Its concentration is measured in parts per million (ppm) and has risen significantly since the pre-industrial era because of fossil fuel combustion and deforestation.
Detailed Explanation:
Let us look at the historical and current values of atmospheric \(\text{CO}_2\):
- Pre-industrial level: The concentration of \(\text{CO}_2\) was approximately \( 280\text{ ppm} \).
- Early 20th century: The levels rose to around \( 290\text{ to } 300\text{ ppm} \).
- Modern/Present-day level: In recent decades, atmospheric monitoring stations (such as the Mauna Loa Observatory) have recorded a steady increase. The concentration crossed \( 400\text{ ppm} \) in 2015 and currently sits between \( 415\text{ and } 420\text{ ppm} \).
Among the given options, \( 400\text{ ppm} \) is the closest approximation to the present atmospheric concentration.

Step 2: Final Answer:
The present concentration of \(\text{CO}_2\) in the atmosphere is approximately \( 400\text{ ppm} \).