Major Sources of the Carbon Dioxide That Is Still in the Air

Whenever you hear about historic carbon emissions by nations in the media, there’s usually a huge omission in the information being transmitted. You’ll often hear about the total CO₂ emissions that nations have emitted throughout history, but not necessarily how much of those emissions are still in the air.

That matters because carbon dioxide in the atmosphere is part of a global carbon cycle. One that begins reducing the emissions generated in any particular year from the very outset from when they were emitted. The following diagram illustrates major parts of the modern Earth’s carbon cycle.

Not shown in the image are other natural sources of carbon dioxide emissions, like volcanoes, and natural sinks that absorb carbon dioxide out of the atmosphere, like oceans.

We’ve updated our estimate of how much CO₂ emissions produced within the modern world’s largest national producers of carbon dioxide emissions since 1850 are still in the air. The following chart updates that data through the end of 2023.

This chart illustrates both total historic emissions and the amount estimated to still be in the atmosphere today, which is the more meaningful value with respect to the modern political debates over climate change.

The chart shows the largest share for any single nation is that for the United States, to which a little over one-fifth of the CO₂ is attributed, where our estimate using this data through 2023 is 21.8%, about a half percent lower than our estimate from two years ago.

China still ranks second by that measure at over 18.1% of the global total, and the combined nations of the European Union come in third at 14.5%. We also find India’s 4.1% share outranks the United Kingdom’s 3.3%, which is remarkable because the U.K. was once the world’s largest producer of carbon dioxide emissions. The “Rest of the World” combines for nearly two-fifth’s of the excess fossil-fuel based carbon dioxide emissions present in the atmosphere as of 2023, which exceeds the United States’ total historic CO₂ emissions.

These relative shares have changed over time, with China and India’s relative contributions to global CO₂ emissions increasing as the relative share of emissions of the United Kingdom, United States, and European Union have declined.

Looking forward, assuming no change in national carbon dioxide emissions from their 2023 levels, we estimate China will become the largest national historical contributor of human-generated carbon dioxide emissions still in the Earth’s air in 2030.

References

Friedlingstein et al. National Fossil CO2 Emissions by Country (Territorial). 2024 v1.0. [Excel Spreadsheet]. 13 November 2024.

Political Calculations. How Long Does Carbon Dioxide Stay in the Atmosphere? [Online Article, Tool]. 19 July 2023.

Image credit: An Interactive Introduction to Organismal and Molecular Biology, 2nd ed. Copyright © 2021 by Andrea M.-K. Bierema is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.