Final answer:
Nitrogen (N2) is not a greenhouse gas and does not contribute to global warming, unlike other gases such as carbon dioxide, methane, and water vapor, which do trap heat in the atmosphere.
Step-by-step explanation:
The gas that is not a greenhouse gas and thereby not responsible for global warming is Nitrogen (N2). Greenhouse gases include water vapor, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), among others. These gases trap heat in the atmosphere and contribute to the greenhouse effect, which warms the planet.
Nitrogen, however, does not have this same effect and is mainly inert in the context of the Earth's atmosphere regarding direct greenhouse warming. While nitrogen is the most abundant gas in the atmosphere, it does not absorb or emit thermal infrared radiation and thus does not contribute to the greenhouse effect.
It's important to note that while water vapor is indeed a powerful greenhouse gas and contributes to the natural greenhouse effect, it mainly responds to changes in atmospheric temperature and does not directly drive climate change.
Instead, human-induced increases in other gases such as carbon dioxide lead to warming, which in turn can increase the amount of water vapor in the atmosphere through evaporation. Consequently, water vapor acts as a feedback mechanism rather than a primary driver of ongoing global warming.