Study Finds Earth’s Carbon Dioxide Levels Are Highest In Human History 

A new study has found that the current carbon dioxide levels on Earth are the highest they’ve been in all of human history.

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According to a study posted to, carbon dioxide (CO2) levels within the Earth’s atmosphere are the highest they’ve been in 14 million years; the entirety of human history. The last time CO2 levels were this high was long before modern day humans existed on Earth.

Bärbel Hönisch, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory, told USA Today that 14 million years ago Earth’s temperature was likely 9 degrees Fahrenheit warmer than today. Michael Mann, a University of Pennsylvania meteorologist not involved in the study, told the publication that back then, the Greenland and West Antarctic ice sheets were non-existent, and the global sea level was around more than 40 feet higher than today.

In a statement from Columbia University, the levels of CO2 are now at 420 parts per million in the atmosphere; pre-Industrial Revolution levels were 280 parts per million. Global temperatures have also rose by around 2 degrees. 

“[This new report] asserts that long-term climate is highly sensitive to greenhouse gas, with cascading effects that may evolve over many millennia.” 

“We have long known that adding CO2 to our atmosphere raises the temperature. This study gives us a much more robust idea of how sensitive the climate is over long time scales,” Hönisch stated

“It’s clear we have already brought the planet into a range of conditions never seen by our species,” Gabriel Bowen, a professor at the University of Utah and study co-author, said. 

USA Today reported that scientists have only been directly measuring CO2 levels within Earth’s atmosphere for the past few decades, so in order to determine past levels, they must use “proxy” sources. These sources revolve around analyzing natural occurrences such as air bubbles trapped in ice cores, the chemical composition of ancient soils as well as ocean sediments, and the anatomy of plant leaves. 

Hönisch stated that the “weathering of rocks on land can act to release CO2 into the atmosphere.” She also cited a recent study published in Nature from the University of Oxford that found that rocks can release CO2 into the atmosphere.

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“Ancient levels of CO2 were higher millions of years ago because of all-natural processes such as volcanoes that produce a lot of carbon dioxide.” 

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Mann stated that those high carbon dioxide levels were able to be maintained for millions of years, making it far more difficult for ice sheets to form like we have today. “We can very likely prevent such levels of warming, ice sheet loss and sea level rise if we reduce carbon emissions substantially in the years ahead,” Mann said.

“If you want us to tell you what the temperature will be in the year 2100, this (study) does not tell you that. But it does have a bearing on present climate policy. It strengthens what we already thought we knew. It also tells us that there are sluggish, cascading effects that will last for thousands of years,” Study co-author Dana Royer, a paleoclimatologist at Wesleyan University, stated. 

“The study confirms the very close relationship between CO2 and global temperatures, and the fact that we’re headed toward CO2 levels not seen in 14 million years, as established in the study, indeed underscores that we’re in uncharted waters,” Mann said.

Mann also added that this particular study “highlights the threat of continued fossil fuel burning at a critical time, as policymakers in Dubai are determining the potential future course of climate action as the window for limiting warming below catastrophic levels begins to close.”