What makes carbon dioxide a greenhouse gas?

The main greenhouse gases found in Earth's atmosphere are carbon dioxide, water vapor, methane, nitrous oxide, and ozone. In the absence of greenhouse gases, the planet's surface would be approximately 15 °C (27 °F) colder on average than it is now, at 14 °C (57 °F).

Like all molecules, carbon dioxide responds differently to various energy wavelengths. The majority of solar energy falls into the visible light spectrum, also known as short wave radiation, with 0.5 microns being the most common wavelength. This wavelength of radiation is very easily absorbed by carbon dioxide and other greenhouse gases, much like x-rays can pass through skin without being blocked.

Instead of passing through Earth, solar energy strikes it and heats it. As a result, electromagnetic energy is released into the atmosphere and becomes sensible heat, or heat that humans can feel. This type of heat falls into the infrared spectrum, also known as long wave radiation. Although the infrared spectrum is fairly wide, the most frequently emitted wavelength is 11 microns, which is what weather satellites display when you see an infrared image.

As a result, it functions very similarly to a greenhouse, where the glass lets sunlight in but prevents heat from easily escaping. Carbon dioxide is to IR radiation what lead is to x-rays: it does not let it pass through.

Carbon dioxide is a greenhouse gas because it has the ability to absorb and emit infrared radiation. This radiation is part of the Earth's heat energy, and when it is absorbed by carbon dioxide molecules in the atmosphere, it causes them to vibrate. These vibrations result in the molecules retaining heat, which contributes to the warming of the Earth's surface and atmosphere. As a result, carbon dioxide traps heat within the Earth's atmosphere, leading to the greenhouse effect.