Carbon dioxide acts as what kind of gas in the atmosphere?

Carbon dioxide is classified as a greenhouse gas due to its ability to absorb and emit infrared radiation. This characteristic plays a significant role in the greenhouse effect, where gases in the atmosphere trap heat, thereby warming the planet. When solar radiation reaches the Earth's surface, some of it is reflected back into space, while greenhouse gases like carbon dioxide effectively capture a portion of this heat, preventing it from escaping and thereby contributing to global warming.

The presence of carbon dioxide in the atmosphere increases the overall temperature through this process, making it integral to discussions about climate change and energy systems. This is in contrast to the other options: carbon dioxide is not a cooling gas, it is not generally classified as a pollutant (though it can contribute to other harmful effects when present in high concentrations), and it is certainly not an inert gas, as inert gases do not react with environmental elements or contribute to climate dynamics.