Question

Which of the following statements is/are TRUE about global warming?

• A. Interception of incoming solar radiation by greenhouse gases in earth's atmosphere is responsible for global warming.
• B. Interception of outgoing longwave radiation by greenhouse gases in earth's atmosphere is responsible for global warming.
• C. Global warming can cause sea level rise.
• D. Carbon dioxide is one of the major greenhouse gases in earth's atmosphere responsible for global warming.

Hint:

Greenhouse gases are largely transparent to incoming shortwave solar radiation but absorb the outgoing longwave (infrared) radiation from the earth's surface.

Answer 1

The Correct Option is B, C, D

Step 1: Recall the basic mechanism of the greenhouse effect.
The sun emits shortwave radiation which passes through the atmosphere and is absorbed by the earth's surface, warming it. The warmed surface re-emits this energy as longwave (infrared) radiation. Greenhouse gases are largely transparent to the incoming shortwave solar radiation, but they strongly absorb the outgoing longwave radiation emitted by the earth's surface, and re-radiate part of it back down, trapping heat within the earth-atmosphere system. This trapping of outgoing longwave radiation is what causes global warming.

Step 2: Examine option (A).
Option (A) states that interception of INCOMING solar radiation causes global warming. This is incorrect, since greenhouse gases mostly allow incoming shortwave solar radiation to pass through relatively unhindered, it is the outgoing longwave radiation that gets absorbed and trapped, not the incoming radiation. So option (A) is FALSE.

Step 3: Examine option (B).
Option (B) correctly states that interception of OUTGOING longwave radiation by greenhouse gases is responsible for global warming. This matches the actual physical mechanism of the greenhouse effect exactly. So option (B) is TRUE.

Step 4: Examine option (C).
Global warming raises average global temperatures, causing thermal expansion of ocean water and accelerated melting of glaciers and polar ice sheets, both of which directly contribute to a rise in sea level. This is a well documented and observed consequence of global warming. So option (C) is TRUE.

Step 5: Examine option (D).
Carbon dioxide (CO2) is indeed one of the most significant greenhouse gases in the earth's atmosphere, released from fossil fuel combustion, deforestation, and industrial processes, and is a major contributor to the enhanced greenhouse effect and global warming, alongside methane, nitrous oxide, and water vapor. So option (D) is TRUE.

Step 6: Conclude.
Statements (B), (C), and (D) are all true descriptions related to global warming, while statement (A) incorrectly identifies incoming solar radiation interception, rather than outgoing longwave radiation interception, as the cause. Hence the correct answers are options (B), (C), and (D).