I heard that carbon dioxide makes up 0.04% of the world’s atmosphere. Not 0.4% or 4%, but 0.04%! How can it be so important in global warming if it’s such a small percentage?

I am often asked how carbon dioxide can have an important effect on global climate when its concentration is so small — just 0.041% of Earth’s atmosphere. And human activities are responsible for just 32% of that amount.

I study the importance of atmospheric gases for air pollution and climate change. The key to carbon dioxide’s strong influence on climate is its ability to absorb heat emitted from our planet’s surface, keeping it from escaping out to space.