CO2 is Regularly Exceeding 410 Parts Per Million for First Time in Human History

During May of 2018, average monthly CO2 values will likely range between 411 and 412 parts per million. A new record for a heat-trapping gas that is causing serious damage to both the Earth’s environment and human civilizations.

(Atmospheric CO2 accumulation since 2007 as depicted by this animation of Mauna Loa Observatory CO2 measurements by Robbie Andrew, of the CICERO Center for International Climate Research.)

There’s one word that best describes this — trouble. And in the most simple terms it means that more unprecedented severe weather, ocean health impacts, and sea level rise is on the way.

Exceeding the 410 PPM Threshold

Last year, atmospheric CO2 levels peaked at around 409.7 parts per million during May of 2018. Hitting just shy of the 410 ppm threshold which will be consistently exceeded this year during the annual peak.

This peak comes during April and May following Northern Hemisphere winter due to seasonal loss of tree leaf photosynthesis that converts a large volume of CO2 into oxygen during summer and fall. As trees return to bloom across the large northern land masses, CO2 concentrations periodically drop.

However, due to human fossil fuel burning, the natural CO2 cycle has, since the 18th Century been significantly thrown out of balance. And as a result, the atmospheric concentrations of this key heat trapping gas rapidly ramped higher and are now in a range not seen in 15-17 million years.

(The CO2 measure at the Mauna Loa Observatory shows a hockey stick like spike in CO2 following a relatively stable period of glaciation and deglaciation over the last 800,000 years. Image source: The Keeling Curve.)

As you can see in the image above, the present period has shown an unprecedented and dangerous rate of atmospheric CO2 increase. One that has no corollary in the past 800,000 years. One that is probably unique in its velocity.

High Levels of Heat Trapping Gases Pose Serious Consequences

Such a great accumulation of heat trapping gases results in serious consequences. Present atmospheric CO2 concentrations, if maintained over multiple Centuries are likely enough to warm the Earth by more than 3 degrees Celsius (significantly more than present warming in the range of 1 to 1.2 C). And such high levels of heat trapping gases — ranging above 410 parts per million — are likely enough to melt significant portions of the world’s ice sheets over Century to multi-Century time scales. During the last climate epoch when atmospheric CO2 exceeded 410 parts per million, the Middle Miocene, sea levels were 100 to 170 feet higher than they are today.

(Atmospheric CO2 levels are now the highest since the Middle Miocene of 15 to 17 million years ago. Image source: Skeptical Science.)

Sea level is not the only system influenced by high atmospheric CO2 levels. And everything from storms to drought intensity, to ocean health, to growing seasons, to typical seasonality, to coral bleaching, and including the Earth’s net ability to support life will ultimately be impacted.

Fossil Fuel Burning is the Primary Cause, Renewable Energy the Primary Solution

As mentioned above, record CO2 emissions brought on by fossil fuel burning is driving the unprecedented atmospheric accumulation we see today. During recent years, very rapid rates of annual accumulation near 3 parts per million (ppm) were achieved as a strong El Nino rippled through the Pacific and reduced the ocean’s ability to draw down carbon. The La Nina years of 2017 and 2018 are seeing these rates of accumulation dip back to near 2 ppm or slightly less as ocean drawdowns have periodically recovered. But more El Nino years are on the way and atmospheric CO2 levels will keep rising so long as mass fossil fuel extraction and burning continues.

(CO2 annual growth rates have proceeded in lock step with increasing rates of fossil fuel burning on decadal time scales. Shorter term fluctuations are driven by the ENSO cycle and large volcanic eruptions. Image source: NOAA ESRL.)

The advance of renewable energy and the reduced use of coal has enabled the world to achieve a slower rate of atmospheric CO2 release growth that appears to be reaching a plateau near 11-12 billion tons of carbon per year. This is still an insane rate of release. However, if the world resolves itself, it can begin to rapidly reduce this severely harmful annual belching of greenhouse gasses. Emergent clean energy technologies like wind, solar, battery storage, and electrical vehicles are providing this hope for response. However, rates of adoption will need to be quite rapid if serious and ever-ramping climate harms are to be avoided. Presently high atmospheric CO2 levels exceeding 410 ppm this year represent a serious hazard. One that we fail to fully address at our peril.


  1. Human emissions of heat trapping gases is not limited to CO2. Methane and other greenhouse gasses produced by industry have resulted in a net CO2 equivalent forcing near 491 parts per million (CO2e). Though CO2 gain is the primary driver of human forced warming, these other gases have an accumulative impact.
  2. I have used the Middle Miocene as a corollary in this analysis due to the fact that present CO2 levels at 410 parts per million and CO2e levels at 491 parts per million (end 2017) generate a rough boundary for both the top and bottom ranges for this climate epoch. It is worth noting that the human forcing is probably more dangerous than that which occurred during the Middle Miocene due to the velocity at which heat trapping gases are accumulating.
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