Study: Carbon Dioxide Levels in Earth’s Atmosphere at Highest Point in Human History
A study released in early December has reported that carbon dioxide levels in Earth’s atmosphere are currently at their highest point in human history. In fact, according to the study, it has been about 14 million years since the level of carbon dioxide (CO2) was this high, which is long before modern humans appeared on the scene.
The report, led by study lead author Bärbel Hönisch, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory, also revealed that at that time, Earth’s temperature was as much as 9 degrees Fahrenheit warmer than today. The Greenland and West Antarctic ice sheets didn’t yet exist, and sea level probably was more than 40 feet higher than it is today, according to University of Pennsylvania meteorologist Michael Mann, who was not part of the study.
The study strengthens the idea that long-term climate is highly sensitive to greenhouse gas, with cascading effects that may evolve over many millennia. Levels of CO2 in the atmosphere are now at 420 parts per million (ppm), up from 280 ppm before the Industrial Revolution. Global temperatures have increased by about 2 degrees over that time.
Study co-author Gabriel Bowen, a professor at the University of Utah, emphasized that “it’s clear we have already brought the planet into a range of conditions never seen by our species.”
Scientists have only directly measured CO2 levels in the atmosphere for the past few decades, so they must use “proxy” sources to determine past levels. The study also emphasizes the close relationship between CO2 and global temperatures and highlights the threat of continued fossil fuel burning at a critical time when policymakers are determining the potential future course of climate action.