With reference to Carbon Dioxide (CO2) as a greenhouse gas, consider the following statements: 1. Forests and oceans act as major sources of carbon…

Correct Option

The correct option is 2 and 3 only.

Explanation

Carbon dioxide (CO₂) is a meteorologically significant variable gas in the atmosphere. It plays a crucial role in the Earth's heat budget by being transparent to incoming solar radiation but opaque to outgoing terrestrial radiation, thereby contributing to the greenhouse effect.

Statement-wise Analysis

• Statement 1 is Incorrect. Forests and oceans act as major sinks (reservoirs that absorb more than they release) of carbon dioxide, not sources. Forests absorb CO₂ through photosynthesis, and oceans absorb it through dissolution and biological processes (phytoplankton). Sources primarily include volcanic activity, respiration, decay of organic matter, and anthropogenic activities like fossil fuel burning.
• Statement 2 is Correct. In the context of atmospheric chemistry and physical geography, the time taken for atmospheric CO₂ to adjust to changes in sources and sinks (often referred to as the adjustment time or residence time in specific models) is estimated to be approximately 20 to 50 years.
• Statement 3 is Correct. The concentration of carbon dioxide in the atmosphere has been increasing steadily due to anthropogenic factors. The rate of increase is estimated to be about 0.5 % annually.

Key Takeaway

Carbon Dioxide (CO₂) is a primary greenhouse gas for which forests and oceans serve as natural sinks. Its atmospheric concentration is rising annually due to the burning of fossil fuels and land-use changes.