Correct Option
The correct option is 2 and 3 only.
Explanation
The atmosphere consists of a mixture of gases classified into permanent gases and variable gases. Permanent gases maintain a fixed proportion in the total volume of the lower atmosphere, while variable gases change in concentration due to natural and anthropogenic processes.
Statement-wise Analysis
- Statement 1 is Incorrect: Carbon dioxide (CO2) is a variable gas. Its volume has not remained constant; it has been rising steadily over the past few decades. This increase is a significant concern regarding global warming and climate change.
- Statement 2 is Correct: The major gases such as Nitrogen (78.08%), Oxygen (20.95%), and Argon (0.93%) are considered permanent gases. Their relative percentages in the atmosphere remain virtually constant over recent history, unlike variable gases such as CO2, water vapour, and ozone.
- Statement 3 is Correct: The rapid rise in atmospheric carbon dioxide concentration is primarily attributed to human activities. The burning of fossil fuels (coal, oil, and natural gas) releases large amounts of CO2, altering the natural balance of the atmosphere.
Key Takeaway
Key Takeaway: Nitrogen and Oxygen are permanent gases with constant proportions, whereas Carbon Dioxide is a variable gas whose concentration is increasing mainly due to fossil fuel combustion.