Posted on 7 June 2025 by Sue Bin Park

Skeptical Science is partnering with Gigafact to produce fact briefs — bite-sized fact checks of trending claims. You can submit claims you think need checking via the tipline.

Are CO2 measurements reliable?

Measurements of the amount of carbon dioxide in the atmosphere are consistent, reliable, and globally verified across multiple independent systems.

NOAA collects data from over 60 sites, including Mauna Loa, which has hosted the longest continuous CO2 record, tracking an annual increase in CO2 from 0.94 ppm in 1959 to 3.33 ppm in 2024. Mauna Loa is ideal due to its remote location and clean Pacific air, while occasional volcanic emissions are well understood and mathematically filtered out of records. 

In addition, hundreds of stations all over the world report to independent monitoring bodies such as the World Meteorological Organization and Europe’s Integrated Carbon Observation System.

Because CO2 mixes evenly in the atmosphere, measurements from multiple systems such as ground stations, air flasks, and orbiting instruments indicate the same story: rising CO2 levels driven by human emissions. Claims of distortion are unfounded and ignore decades of careful monitoring.

Go to full rebuttal on Skeptical Science or to the fact brief on Gigafact

This fact brief is responsive to quotes such as this one.

Sources

NOAA Tracking carbon dioxide across the globe

NOAA How we measure background CO2 levels on Mauna Loa

NOAA What is the Global Greenhouse Gas Reference Network?

NASA How do scientists know that Mauna Loa’s volcanic emissions don’t affect the carbon dioxide data collected there?

NOAA Annual Mean Growth Rate for Mauna Loa, Hawaii

World Meteorological Organization Atmospheric CO2 monitoring continues despite Mauna Loa volcanic disruption: AEMET (Spain)

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.