Which gas is often considered a trace component in the atmosphere, making up only about 0.04%?

Carbon dioxide is often considered a trace component in the atmosphere, comprising about 0.04% of the total atmospheric gases. Despite being a small fraction, carbon dioxide plays a crucial role in the Earth’s climate and life processes. It is a key greenhouse gas, which means it helps trap heat in the atmosphere, contributing to the greenhouse effect. Additionally, carbon dioxide is essential for photosynthesis, where plants convert it into oxygen and glucose, thereby sustaining life on Earth.

The other gases listed, while also present in the atmosphere, do not occupy the same exceptionally small percentage as carbon dioxide. Neon is present in trace amounts, but at around 0.0018%, and argon makes up about 0.93% of the atmosphere, both of which are significantly higher proportions. Ozone, while important for absorbing harmful ultraviolet radiation in the stratosphere, is also present in very small concentrations compared to carbon dioxide, particularly in the troposphere. However, carbon dioxide's impact on climate change and biological processes makes its trace presence particularly significant.