A Greek-Australian researcher is one of the scientists penning a new article describing just how carbon dioxide in the atmosphere affects the formation of glaciers and its crucial role in climate change.
The research was undertaken by Vera Korasidis, a palynologist, or scientist who studies pollen and pollen fossils, and her colleague Peter Buck, a Postdoctoral Fellow at the Smithsonian’s National Museum of Natural History, who co-authored the paper.
They believe that a drop in greenhouse gases, including carbon dioxide, caused a great global cooling event some 34 million years ago.
This unfortunately means that, conversely, a rise in such gases would inevitably mean an equal-sized global warming event, as has long been thought by climate scientists.
The ultimate manifestations of global warming are disputed by some, who see them as the normal fluctuations in climate as we have seen throughout the history of the planet.
Antarctica “covered in lush rainforests” before global cooling event
But there is no disputing that the more carbon dioxide in the planet’s atmosphere, the warmer that atmosphere will become.
This is the first time that researchers have shown in a study that global cooling, as a result of less available carbon dioxide, created the massive glaciers that formed 34 million years ago.
The new paper, which was published in the journal Nature Geoscience, states that the decrease of this greenhouse gas at that time caused what the scientists called an “icehouse state.”
Korasidis notes that “Before then, vast regions of the world, including Antarctica, were covered in lush rainforests. There were no permanent ice sheets” on Earth.
During these many years, known as the “Eocene Oligocene transition,” the average average temperature across the entire globe decreased by more than 5.4 degrees Fahrenheit (3 degrees Celsius) in approximately 300,000 years.
Vittoria Lauretano, the lead author of the paper, works as an organic geochemist in the realm of the paleoclimate at the University of Bristol’s Organic Geochemistry Unit. She states “This geologically quick change shows how atmospheric carbon dioxide drives major shifts in climate.”
Evidence from marine sediments shows unequivocally that the globe indeed was a very temperate place prior to that era, with not even a glacier anywhere on Earth.
David Naafs, a colleague of Lauretano’s at the University of Bristol’s Organic Geochemistry Unit and another co-author of the paper, noted “Geologically speaking, it happened pretty fast. Antarctica hadn’t been glacial before that for a very long time.”
It was much harder to find such evidence on land, however, showing just how the decrease in carbon dioxide caused the cooling of the earth.
Brian Huber, a Smithsonian natural History paleoclimatologist, who was not involved in the research, notes that “Usually, we don’t get temperatures from land-based records. But this research uses a new approach to find those past temperatures in soft coal across that transition.”
The coal deposits in southeast Australia are giving up their secrets to the team of researchers, with their layers, put down during that crucial Eocene-Oligocene cooling period, showing just such evidence.
Korasidis’ team looked at the properties of microscopic fossils from bacterial lipids, or fats, that had been preserved in coal from the Eocene and the Oligocene epochs, and across the transition, when the cooling occurred.
Exactly how these lipids are constructed changes — based on the temperature of the environment at that time.
“If you have bacteria growing at a high temperature, they will make lipids that look a certain way. If the bacteria grow at a cold temperature, their lipids will look different,” Naafs explained. “We can look for those changes in fossils to find signs of climate change.”
In addition, coal “also only forms on land, so it provides a unique terrestrial record,” said Korasidis, adding “Australia, especially, has the thickest Eocene-Oligocene coal reserves in the world.”
When examining the coal, Lauretano and Naafs discovered evidence of the same drop in land temperatures as had already been seen in marine records.
Korasidis lent further credence to her findings by confirming, by looking at the plant pollen that is preserved in coal, that plant populations changed during this era to favor those that thrive in colder climates.
“The key to this study is that we found really similar trends between what happened on land and in the ocean, so we realized there must be a global mechanism driving behind it,” said Korasidis.
Up until now, scientists ha don’t known why the Eocene Oligocene transition to a much cooler climate had occurred. One theory had been that there had been a change in the currents of the Antarctic ocean. Eventually that theory was discarded.
“The question has always been what was driving this change,” Naafs pointed out.
By this research, and the creation of a climate model, the scientists found that only a decrease in atmospheric carbon dioxide could have occasioned such a major drop in temperatures in the span of 300,000 years — which is the blink of an eye in geological terms.
“It’s only when you include carbon dioxide that this transition happens in the models in the way we see it in the data. If you don’t lower it, you can’t cool the world enough to build new ice sheets,” Lauretano, the paper’s lead author, explains.
The team’s findings indeed back up the theory that carbon dioxide plays a significant role in any climate change on the earth.
The scientists used models created by the Bristol Research Initiative for the Dynamic Global Environment. These also had shown with accuracy how climate change has occurred over time in the past, which lends credence to how they predict future climate change.
Naafs stated “The work we’ve done also calibrates these climate models to see how well they’re doing. We need them and the geologic record to understand how Earth’s system operates.
“And the main message we’ve found is carbon dioxide is in the driver’s seat.”