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FACT BRIEF

Can CO2 be ignored because it’s just a trace gas?

By Sue Bin Park
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NO

While carbon dioxide is a small part of the atmosphere, it has a large impact on climate as a greenhouse gas.

Nitrogen and oxygen make up around 99% of the atmosphere, but neither traps heat. Less than 0.05% of the atmosphere is made up of greenhouse gases, which do.

Without greenhouse gases, the Earth would be too cold to support most life, with average temperatures 2° F below zero (-18° C).

On the other hand, increasing greenhouse gas concentrations elevates temperatures. Human activities such as fossil fuel burning have raised CO2 concentrations from 280 parts per million in pre-industrial times to 424 parts per million in 2024. Over the same period, the planet has warmed 2° F (1.3° C) on average.

Climate scientists agree that emissions of CO2 and other greenhouse gases are responsible for this observed rise in temperature despite their relatively low concentration in the atmosphere.

See a full discussion of this at Skeptical Science
This fact brief is responsive to conversations such as this one.
Sources
NASA Carbon Dioxide
MIT Climate Portal How do greenhouse gases trap heat in the atmosphere?
Columbia Climate School You Asked: If CO2 Is Only 0.04% of the Atmosphere, How Does it Drive Global Warming?
NASA Steamy Relationships: How Atmospheric Water Vapor Amplifies Earth’s Greenhouse Effect
EIA Energy and the environment explained
Carbon Brief State of the climate: 2024 sets a new record as the first year above 1.5C
ABOUT THE CONTRIBUTOR
Skeptical Science
Skeptical Science is a non-profit science education organization. Our goal is to remove a roadblock to climate action by building public resilience against climate misinformation. We achieve this by publishing debunking of climate myths as well as providing resources for educators, communicators, scientists, and the general public. Skeptical Science was founded and is led by John Cook, a Senior Research Fellow with the Melbourne Centre for Behaviour Change at the University of Melbourne.
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Fact briefs are short, credibly sourced summaries that offer “yes/no” answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact —a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all fact briefs here.