Carbon dioxide (CO2) is the greenhouse gas with the largest concentration in the atmosphere.

Explanation:

Carbon dioxide is a naturally occurring greenhouse gas that is essential for life on Earth. It is produced through natural processes such as respiration and volcanic activity, as well as through human activities such as burning fossil fuels and deforestation.

Key Points:
- Carbon dioxide is a greenhouse gas, meaning it traps heat in the atmosphere and contributes to the greenhouse effect.
- The concentration of carbon dioxide in the atmosphere has been increasing rapidly since the Industrial Revolution, primarily due to human activities.
- Carbon dioxide is the most abundant long-lived greenhouse gas in the atmosphere, accounting for about 75% of the total greenhouse gas concentration.
- It has a long atmospheric lifetime, meaning it can remain in the atmosphere for hundreds of years.
- The increase in carbon dioxide concentration is a major driver of climate change, as it leads to the warming of the Earth's surface and changes in weather patterns.
- The burning of fossil fuels, such as coal, oil, and natural gas, is the primary source of carbon dioxide emissions.
- Deforestation also contributes to carbon dioxide levels, as trees absorb carbon dioxide during photosynthesis and release it when they are burned or decay.
- The concentration of carbon dioxide in the atmosphere is measured in parts per million (ppm). Before the Industrial Revolution, the concentration was around 280 ppm, but it has now surpassed 400 ppm and continues to rise.

Conclusion:

In summary, carbon dioxide is the greenhouse gas with the largest concentration in the atmosphere. Its increasing levels are primarily caused by human activities, such as burning fossil fuels and deforestation, and it is a major contributor to climate change.