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Mauna Loa* CO2 Levels

in recorded human history
(and millions of years before that) 



Scripps MLO 


425.01 ppm

Apr 28 2023

web & plot  

424.22 ppm**

Apr 26 2023



424.64 ppm

May 28 - Jun 3, 2023


423.95 ppm**

April 23-29, 2023


424.00 ppm

May 2023


423.78 ppm**

May 2023



 418.56 ppm



 416.45 ppm


monthly data averaged

* Mauna Loa record includes CO2 measurments at Maunakea site in 2022-2023  
** All-time high in the Scripps measurements of CO2 at Mauna Loa 


Marking the latest CO2 records is not an act of celebration, but of bearing witness.  

The achievements are a sobering reminder of the chemical changes that we humans are collectively making to the atmosphere--changes with disruptive impacts that affect every living being in the biosphere.  When a new record is reached, it is is marked here with an invitation for people to take notice, reflect on the transformation that is going in the wrong direction, and resolve to reverse these trends.

Reversing the trend is not something that any one person can achieve on their own.  But individuals and groups can build on this CO2 Earth initiative by taking steps that help make the CO2 indicator for planetary health as ubiqutious as our stock market updates and weather reports.  Consider sharing the CO2 Earth updates and records with people and groups that are part of your information-sharing circle.  



A New Daily High Each Year

The graphic below from Teem Earth partner @NumberLens presents NOAA CO2 readings since 1999 to show the seasonal peak for daily CO2 readings at Mauna Loa.  It shows that CO2 levels usually peak in April or May, a phenomena discovered by Charles David Keeling in the late 1950s and early 1960s when he began what became the world's longest-running, high preceision record of direct measurements of CO2 in background air.  

2020 06 01 dly co2 high since 1999 mlo noaa



*Atmospheric CO2 is higher now than at any time in the past 200,000 years of human history.  In fact, studies of past CO2 levels have accumulated evidence of CO2 levels being lower than 400 ppm for the past 23 million years.  That makes the CO2 records on this page the highest in human history plus a period that's a hundred times short 200,000-year time that homo sapiens have graced the earth.   The higher levels of this planet-heating gas is just one part of the problem.    The other is the speed of the changes, more than a hundred times pre-human times, and faster than many ecosystems can adapt to.  



Related Links

Science Daily Jun 2020 | Today's atmospheric CO2 levels greater than 23 million-year record 

Geology 2020 | A 23 m.y. record of low atmospheric CO2  

CO2 Earth | Daily CO2

CO2 Earth | CO2 Proxy Data

CO2 Earth | CO2 Acceleration

CO2 Earth | Examples of CO2 Media Broadcasts

CO2 Earth | CO2 for Print