Final answer:
A chemical must have the ability to absorb and scatter energy, as well as a long residence time in the atmosphere, to be considered a greenhouse gas.
Step-by-step explanation:
In order to be considered a greenhouse gas, a chemical must have two properties:
- Ability to absorb and scatter energy: Greenhouse gases are able to absorb and scatter infrared radiation, which leads to the trapping of heat in the Earth's atmosphere. This property is measured by the global warming potential (GWP) of each greenhouse gas.
- Long residence time in the atmosphere: Greenhouse gases must have a long lifetime in the atmosphere in order to have a significant impact on the greenhouse effect. The longer a greenhouse gas remains in the atmosphere, the more heat it can trap.
For example, methane has a strong ability to absorb and scatter infrared radiation, and it has a relatively long lifetime in the atmosphere, making it a potent greenhouse gas.