Which gas is a significant contributor to the greenhouse effect?

Carbon dioxide is a significant contributor to the greenhouse effect primarily due to its ability to absorb and re-radiate infrared radiation. The greenhouse effect is a natural phenomenon where certain gases in the Earth's atmosphere trap heat, preventing it from escaping back into space. This process is essential for maintaining life as it keeps the Earth's surface warm enough to support ecosystems.

Carbon dioxide is released into the atmosphere through human activities such as the burning of fossil fuels, deforestation, and various industrial processes. Its concentration in the atmosphere has increased significantly since the industrial revolution, leading to enhanced greenhouse effect and resultant climate change. Unlike other gases listed, such as helium, nitrogen, and argon, carbon dioxide has properties that enable it to interact with infrared radiation, making it a potent greenhouse gas.

While nitrogen and argon are abundant gases in the atmosphere, they do not contribute to the greenhouse effect in a meaningful way because they do not absorb infrared radiation. Helium, being a noble gas, is also non-reactive and lacks the necessary molecular structure to absorb heat. Therefore, among the choices, carbon dioxide is the key gas that plays a critical role in the greenhouse effect and climate dynamics.