CO2 Levels In Earth's Atmosphere Just Reached Highest In Human History


Tom Hale

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

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Mauna Loa Observatory.

Measurements of CO2 concentration have been carried out at Hawaii’s Mauna Loa Observatory since 1958, making its record the longest unbroken measurement of co2 in the atmosphere. Image credit: Chris Finch Photography/

April 2022 saw levels of carbon dioxide in Earth’s atmosphere tip over 420 parts per million (ppm) — that’s the highest level ever recorded in human history. 

The Scripps Institution of Oceanography at UC San Diego reported that the monthly mean baseline carbon dioxide (CO2) for April 2022 at Hawaii’s Mauna Loa Observatory was 420.02 ppm. This was later backed by recordings from the National Oceanic and Atmospheric Administration (NOAA), with their data showing levels reached 421.33 ppm on May 4, 2022.


The figures are a startling indication of how human activity is radically changing our planet — and how we're not doing nearly enough to remedy our impact.

Carbon dioxide is one of the most important greenhouse gases linked to climate change as it lingers in Earth's atmosphere for centuries. Although naturally found in trace levels in Earth’s atmosphere, the concentration of this heat-trapping gas has been increasing since the Industry Revolution in the 19th century as it’s released through human activities such as burning fossil fuels and deforestation. 

Hawaii’s Mauna Loa Observatory is used as a global background reference for CO2 in the atmosphere because of its high altitude and remote location. Measurements of carbon dioxide concentration have been carried out here since 1958 — when levels of carbon dioxide were less than 320 ppm — making its record the longest unbroken measurement of carbon dioxide in the atmosphere. 

This new data is considered preliminary for now, but it follows a clear trend that's been unfolding over recent decades. Year on year, the level of carbon dioxide recorded at the Mauna Loa Observatory has been steadily rising with ppm reaching consistently above 400 over the past decade. For a little context, the last time global carbon dioxide levels were consistently above 400 ppm was around 4 million years ago, a period when the world was about 3°C (5.4°F) hotter and sea levels were much higher than today.


There is some seasonal fluctuation of carbon dioxide in the atmosphere with the highest monthly mean value occurring in May, just before plants in the northern hemisphere start to suck up large amounts of carbon dioxide from the atmosphere during the spring growing season. This means May's monthly average is set to be even higher than April's. 

"It is likely May will be higher still," Pieter Tans, a senior scientist in NOAA's Climate Monitoring and Diagnostics Laboratory, told Axios.

"We really need to focus on decreasing emissions and we haven't had much success globally because the rate of increase of CO2 remains as high as it has been in the last decade."


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