What are the major components of the modern atmosphere and how have human activities altered levels of CO2?

What are the major components of the modern atmosphere and how have human activities altered levels of CO2?

• A. Predominantly nitrogen and oxygen; human activities have increased CO2 levels, contributing to climate change.
• B. Predominantly carbon dioxide and methane; human activities have decreased CO2 levels.
• C. Mostly helium and neon; CO2 remains constant.
• D. Oxygen and argon; CO2 fluctuates but not linked to human activity.

Answer: (A)

The atmosphere is dominated by nitrogen and oxygen, which make up the vast majority of air. The remaining gases, including carbon dioxide, argon, neon, and others, are present in much smaller amounts. Carbon dioxide is a trace gas, but it has a big impact on climate because it traps heat in the atmosphere. Human activities—mainly burning fossil fuels like coal, oil, and gas, plus cement production and some land-use changes—have increased CO2 concentrations from about 280 parts per million before the industrial era to well over 400 ppm today. This rise strengthens the greenhouse effect and is linked to ongoing climate change. The other options misstate either the main constituents or the relationship between human activity and CO2 levels.

The atmosphere is dominated by nitrogen and oxygen, which make up the vast majority of air. The remaining gases, including carbon dioxide, argon, neon, and others, are present in much smaller amounts. Carbon dioxide is a trace gas, but it has a big impact on climate because it traps heat in the atmosphere. Human activities—mainly burning fossil fuels like coal, oil, and gas, plus cement production and some land-use changes—have increased CO2 concentrations from about 280 parts per million before the industrial era to well over 400 ppm today. This rise strengthens the greenhouse effect and is linked to ongoing climate change. The other options misstate either the main constituents or the relationship between human activity and CO2 levels.