Human activities in the recent past have caused the increased concentration of carbon dioxide in the atmosphere, but a lot of it does not remain in the lower atmosphere because of Which of the statements given above is/are correct?

Answer: (c) 2 and 3

Phytoplankton and polar ice hold some CO₂; movement into the stratosphere does not remove it from the atmosphere.

Statement by statement

1. ✗ WRONG CO₂ mixes into the stratosphere too, but this does not remove it from the atmosphere.

2. ✓ CORRECT Phytoplankton take up CO₂ through photosynthesis.

3. ✓ CORRECT Air bubbles trapped in polar ice store small amounts of gases.

The idea

Only about half of the carbon dioxide we emit stays in the air. The rest is taken up by sinks. The ocean takes about a quarter, partly by dissolving it and partly through tiny floating plants (phytoplankton) that use it in photosynthesis. Land plants and soils take most of the rest.

CO₂ dissolves in surface sea water → Phytoplankton use it in photosynthesis → They are eaten or die → Remains sink to the deep sea → Carbon is locked away for centuries

The trap

CO₂ mixes throughout the atmosphere; moving into the stratosphere does not remove it from the atmosphere.

Also know

This is called the biological pump. The cost of the ocean’s service is ocean acidification: dissolved CO₂ forms carbonic acid, which makes it harder for corals and shell animals to build their skeletons. Air bubbles in polar ice hold only a tiny amount of gas, but they are a record of the atmosphere going back about 800,000 years.