Fact brief – Can CO2 be ignored because it’s just a trace gas?
Posted on 18 January 2025 by Guest Author
Skeptical Science is partnering with Gigafact to produce fact briefs — bite-sized fact checks of trending claims. This fact brief was written by Sue Bin Park from the Gigafact team in collaboration with members from our team. You can submit claims you think need checking via the tipline.
Can CO2 be ignored because it’s just a trace gas?
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.
Go to full rebuttal on Skeptical Science or to the fact brief on Gigafact
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 fact briefs published on Gigafact
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 of our published fact briefs here.
