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Atmospheric Carbon Levels: May 2023 Update


By Tom Abrams, CFA  |  June 29, 2023

There are dozens of locations worldwide where atmospheric greenhouse gas (GHG) levels are recorded and tracked. At the NOAA's Mauna Loa and Maunakea observatories, CO2 levels over the past few decades have steadily increased. May 2023 data, which is usually the seasonal peak for the annual cycle (vertical lines), is now in hand and shown in the data below. The NOAA website also contains information on atmospheric methane, nitrous oxide, and sulfur hexafluoride GHG levels. This Insight updates an earlier Mauna Loa Insight published in November 2022.


Source: NOAA

Coupled with multiple sets of research on evidencing ancient greenhouse gas levels, the NOAA has stitched together how the more recent trend connects to the long history of atmospheric greenhouse gas levels. Yes, it has cycled over time, but clearly, the graph’s extension during the past few decades is extra-cyclical relative to history. Major variables thought to have driven the increase in atmospheric CO2 revolve around the industrial age. They include meaningful population growth, the vast expansion in transportation, and power from fossil fuels.

Parts Per Million

The oft-quoted goal to limit global warming to below 1.5 degrees Celsius (~3 degrees F) is directly linked to a PPM (part per million) level of greenhouse gases in the atmosphere. Although there are different estimates of critical PPM levels, many associate 450 PPM as the level that would lead to a 1.5 degree C warming. PPM above that level would cause greater warming. Scientific articles seem to suggest 500 PPM as a level linked to a 2.6 degree Celsius (~5 degree F) increase. Increases are from a pre-industrial measurement of surface temperatures.

It is clear the world is increasingly focused on reducing carbon emissions, and every month more projects and changes are announced to move in that direction. So what’s the progress?

Unfortunately, not much at all, according to the NOAA chart below. PPM accumulation per year (red line below) continues to hover in the 2.0 - 2.5 PPM range.


Source: NOAA

Tracking how fast the atmosphere approaches key levels is critical for knowing how soon 450 PPM or higher levels will be reached. To calculate this, take the number of PPMs between the May reading of 424 and 450 (approx. 26) and divided that number by ~3, the year-over-year monthly PPM increase (6-month moving average). The resulting 14.3 tells us how many more years at the current rate of PPM increase before the 450 PPM level and the estimated 1.5 degrees Celsius (~3 degrees F) global warming are reached: 2037. To extend the 15.5 years left before 450 PPM is reached, the rate of increase in PPM has to decrease and ultimately reach no growth—or net zero—to plateau at that level.

A similar calculation using 500 PPM as a level associated with the 2.6 degree Celsius (~5 degrees F) indicates 37.6 years from now, or 2059. This would be much sooner than many long-term forecasts calculate with assumptions of a declining rate of CO2 accumulation and net zero increases in 2050 or 2060. The graph below shows the result of this calculation over time with the blue line for 450 PPM and the orange line for 500 PPM.


Source: NOAA

There are a number of big variables sometimes mentioned by climate analysts as impacting the trend accumulation of CO2 in the atmosphere. One factor that could have slowed CO2 build up in the 2020-2021 period was the Covid-induced economic slowdown followed by the Covid lockdowns in China. The economic reacceleration in 2022 likely supported PPM additions as has the Russian invasion of Ukraine which has resulted in increasing global coal burn. Ironically, some climate watchers note a silver lining of an economic slowdown would be less PPM produced and more time for climate action to have a bite in emissions. However you look at the factors – and no doubt it is much more complicated than just these few – better emission reduction results are required to bring this statistic down.

Motivations to slow the rate of carbon accumulation in the atmosphere seem to be building. Given there are no magic solutions to stem rising CO2 levels, we will continue to hope that the thousands of smaller efforts will begin to add up to a significant PPM impact. We’ll check in again when the September 2023 seasonal trough levels are in hand.

In the meantime, FactSet’s ESG products can help in understanding climate developments and risks across portfolios. Those risks only increase with each passing year without decline in the rate of CO2 accumulation.


This blog post is for informational purposes only. The information contained in this blog post is not legal, tax, or investment advice. FactSet does not endorse or recommend any investments and assumes no liability for any consequence relating directly or indirectly to any action or inaction taken based on the information contained in this article.

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Tom Abrams, CFA

Associate Director, Deep Sector Content

Mr. Tom Abrams is the Associate Director for deep sector content at FactSet. In this role, he is responsible for integrating additional energy data onto the FactSet workstation, including drilling, production, cost, regulatory, and price information. Prior, he spent over 30 years working at sell- and buy-side firms, most recently as the sell-side midstream analyst at Morgan Stanley. He also held positions at Columbia Management, Dreyfus, Credit Suisse First Boston, Oppenheimer, and Lord Abbett. Mr. Abrams earned an MBA from the Cornell Graduate School of Business and holds a BA in economics from Hamilton College. He is a CFA charterholder and holds certificates in ESG investing, sustainable investments, and real estate analysis. 


The information contained in this article is not investment advice. FactSet does not endorse or recommend any investments and assumes no liability for any consequence relating directly or indirectly to any action or inaction taken based on the information contained in this article.