It is said, "CO₂ contributes to global warming". Explain?

Carbon dioxide (CO₂) is a greenhouse gas. This means that carbon dioxide is able to trap the heat and prevents it from escaping the Earth’s atmosphere.

When the amount of carbon dioxide in the atmosphere increases, the amount of heat trapped also increases. This makes the average temperature of the Earth rise up making it hotter.

This above average warming up of the Earth’s atmosphere is known as global warming.