While global warming remains at the forefront of the minds of many, researchers from UC Berkeley and other institutions took a closer look at the driving forces of global cooling in a study published Thursday.
The study, conducted through a partnership among UC Berkeley, UC Santa Barbara and a French research institute, was prompted by previous research looking into long-term trends in climate change, according to senior author of the study and UC Berkeley earth and planetary science associate professor Nick Swanson-Hysell. Ultimately, they found that the dominant cause of long-term global cooling was the formation of islands in Southeast Asia.
“It’s well-known that the climate has been cooling over the last 15 million years, and I think for a long time a dominant hypothesis of that cooling was mountain-building in the Himalayas,” said UC Berkeley doctoral student Yuem Park. “This work kind of changes that perspective and provides a new and what we think is a better hypothesis for that cooling.”
This hypothesis stemmed from the observations that the team made about the correlation between mountain-building in the tropics and glacial climates, Swanson-Hysell said.
From increased rock exposure with minerals and a plentiful amount of tropical rain, carbon dioxide is pulled out of the atmosphere and mixes with water to dissolve minerals in these rocks, according to study co-author Eliel Anttila.
The minerals then make their way into the ocean and sequester carbon, removing enough from the atmospheric carbon cycle to cool the planet.
According to Park, the team believes that the emergence of these Southeast Asian islands has decreased the amount of carbon dioxide in the atmosphere by 200 to 400 parts per million over the past 15 million years. In just over 100 years, however, humans have released over 100 parts per million.
“Putting that in perspective, it’s kind of shocking, how quickly we were able to reverse the effects of these processes that took millions of years to accomplish,” Park said.
To confirm its hypothesis, the team traveled to Toulouse, France and collaborated with Yves Goddéris of Géosciences Environnement Toulouse to build upon his GEOCLIM computational model and estimate how the growth of Southeast Asian islands has altered atmospheric carbon levels, according to a Berkeley News article.
Swanson-Hysell said the collaborative effort was largely enabled by the funding and support of about $11,000 from the France-Berkeley Fund, or FBF, and about $745,000 from the National Science Foundation’s Frontier Research in Earth Sciences program.
According to FBF program manager Julia Nelsen, the study reflected FBF’s mission to support early career researchers and extended collaboration between France and UC Berkeley.
“We like to find projects that show signs of promise that they will lead to long-term collaborations and really foster these deep relationships between the Berkeley campus and France,” Nelsen said. “In this case, I guess we were right about that because that’s exactly what it did.”