Researchers at the University of Bergen have discovered that the Earth 35-60 million years ago may have been much warmer than scientists originally thought. Through their research, Professor Nele Meckler and her colleagues at the university hope to learn more about how our environment reacts to an excess of greenhouse gases in the atmosphere.
Previously, scientists relied heavily on data obtained by observing oxygen isotopes taken from sediments hundreds of meters underwater. Trapped in the sediment is a mix of heavier and lighter variations of oxygen, which show a sort of history of what the climate was like millions of years ago.
When researchers observed a period of heavy oxygen isotopes, it was assumed that it indicated a period of cooler temperatures. Conversely, lighter oxygen meant a period of warmer temperatures.
However, this technique could be complicated and confusing due to various factors influencing heavy and light pockets of oxygen isotopes. For example, ocean salinity could change oxygen concentration, and the amount of ice locked away in the polar regions could also affect the results.
Meckler and her team chose instead to observe similar oxygen concentrations in the shells of ancient minuscule creatures, known as benthic foraminifera or “forams.”
Due to thermodynamics, oxygen molecules would “clump” in the calcium shells of these forams when temperatures were colder. When it was warmer, the molecules would be more spread out. This gave Meckler a more accurate look into the climate millions of years ago.
Using the foram method, researchers found that 57 and 52 million years ago, the North Atlantic was roughly 20 degrees Celcius (68 degrees Fahrenheit). “That’s a whole lot warmer,” commented Meckler, citing that the previous data showed estimates of 12-14 degrees Celcius (53.6-57.2 degrees Fahrenheit).
The paper from the research team claims that greenhouse gases could have a higher “warming effect” than previously thought. This effect refers to the capacity that greenhouse gases have to heat our atmosphere, depending on the concentration. If true, this could mean that gas emissions could be making the earth much warmer than we think.
However, Meckler says that the data needs much more observation before a definitive conclusion can be reached. “I do want to want to put a caveat here that we have only looked at the Atlantic Ocean so far, so it could be that the Atlantic Ocean is doing something special,” she said. She hopes to reproduce the study across different ocean basins to confirm her results.
John Eiler, a scientist at CalTech who pioneered the use of clumped isotopes to measure ancient temperatures, said of Meckler’s study, “This is a highly significant study that both advances our understanding of the deep ocean during periods of sustained globally warm climate and challenges longstanding interpretations of the temperature structure of the oceans during ‘greenhouse’ eras.”