What are greenhouse gases ? Name two GHGs.

Explanation

**Step-by-Step Solution:**

1. **Definition of Greenhouse Gases (GHGs):**
Greenhouse gases are gases in the Earth's atmosphere that have the ability to absorb and re-radiate infrared radiation. This process contributes to the greenhouse effect, which leads to global warming.

2. **Mechanism of Action:**
The key characteristic of greenhouse gases is their capacity to re-radiate infrared radiation. When the Earth's surface absorbs sunlight, it emits this energy in the form of infrared radiation. Greenhouse gases trap some of this radiation, preventing it from escaping back into space, thus warming the atmosphere.

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