Extreme CO2 Buildup Could Explain Skyrocketing Temperatures During Earth’s Early Years

Researchers on Monday said high levels of CO2 in Earth’s early atmosphere could explain multiple unanswered geographic phenomenon that have long plagued researchers.

In this Nov. 28, 2019 file photo, smoke and steam rise from a coal processing plant in Hejin in central China’s Shanxi Province. (AP Photo/Sam McNeil)

(CN) — New research suggests that Earth’s abnormally high temperatures during its formative years could be explained by an issue humankind continues to grapple with today — an excessive amount of carbon dioxide in the atmosphere.

For years, scientists have labored to solve a perplexing riddle surrounding Earth and its earliest years in our solar system: How was Earth able to maintain such a hot climate roughly 4 billion years ago despite the fact that our sun at the time only illuminated the planet with around three quarters of the power it is capable of today?

Experts point to the lack of any major glaciers on the planet during this time as evidence of a strangely warm climate, but have never been able to nail down an explanation for the conundrum. The question is so famous among scientific circles it has even been gifted a name — the paradox of the young weak sun.

The prevailing explanation for the phenomenon suggests some greenhouse gas likely kept the planet so warm and new research now reveals that massive amounts of carbon dioxide may have been the culprit behind this paradox all along.

In a study published Monday in Proceedings of the National Academy of Sciences, researchers reveal that the most likely greenhouse gas to explain Earth’s high temperatures billions of years ago is CO2. While other trace gases like helium could also serve as an explanation, experts in Monday’s study believe that when you look at the entire identity of Earth during its infancy, CO2 is the only logical gas that kept the planet from transforming into a giant ball of ice.

To explain this, scientists point to another phenomenon of Earth’s early years; ocean temperatures that were way too high. While today’s average ocean surface temperatures lingers around 68 degrees Fahrenheit, ocean temperatures a few billion years ago were around an astounding 160 degrees — warmer than any ocean temperature ever recorded in modern history.

Daniel Herwartz of the University of Cologne in Germany and one of the authors of the study says that high enough concentrations of CO2 in the atmosphere would have changed the ocean’s composition enough to make these high temperatures possible and would explain Earth’s toasty climate in the process.

“High CO2 levels would thus explain two phenomena at once: first, the warm climate on Earth, and second, why geothermometers appear to show hot seawater,” Herwartz said in a statement. “Taking into account the different oxygen isotope ratio of seawater, we would arrive at temperatures closer to 40°C.”

Experts say this explanation for the weak sun paradox and Earth’s record-breaking ocean temperatures fits into our understanding of the carbon cycle. While carbon dioxide occurs naturally in Earth’s atmosphere, the gas eventually becomes trapped in carbon reservoirs around the globe like coal, oil and gas deposits.

But these reservoirs typically only exist on continental landmasses, and in Earth’s formative years, there weren’t a lot of those around. It took millions of years for tectonic forces to forge Earth’s landmasses, allowing oceans to dominate most of Earth’s early surface.  

Thorsten Nagel from Aarhus University in Denmark and another author of Monday’s study says this lack of carbon containers for Earth’s CO2 collection further supports their theory that carbon dioxide was the cause behind Earth’s bizarrely high temperatures.

“That also explains the enormous CO2 levels of the young Earth from today’s perspective,” Nagel said. “After all, roughly three billion years ago, plate tectonics and the development of land masses in which carbon could be stored over a long period of time was just picking up speed.”

Of course Earth did not stay this way for long. Over time Earth’s tectonic plates gave rise to enough mountain ranges and other landmasses that gave CO2 a way out of the atmosphere and into the ground. Eventually CO2 levels dropped enough that it allowed colder temperatures and repeated ice ages to wrest control of the planet away from the constant heat, and ultimately, allowed the planet to settle into the form we know today. 

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