Unearthing deep climates: the journey of a climate historian

Timothy D. Herbert

Timothy D. Herbert

AT VARIOUS POINTS in Earth’s four-and-a-half billion-year history, Timothy Herbert‘s home in Providence, Rhode Island has been covered by ice and tropical rainforest. Through an intricate exchange between earth, ocean and sky, our planet’s climate has gone through dramatic changes.

Herbert, a geologist and climate historian, has devoted his career to reconstructing these events and figuring out why they happened. In the thick of the fight over climate change, he is turning his gaze back in time in the hopes that history holds important clues about future climate patterns and the ways in which people might influence them. His research team looks for smoking guns, markers of marine life, to point them in the direction of past climate cycles.

His love for going back in time started with his childhood fascination with archaeology. “It was this world I could go in my imagination,” he said. “I think that was a foray into thinking about time and history in the long-term.”

Now, Herbert deals with a different kind of history. In his lab at Brown University he and his colleagues collect and analyze columns of mud from the ocean floor that contain evidence about what our planet may have looked like hundreds of millions of years ago. A 10-meter column can contain mud that has accumulated over millions of years.

From these sediment cores, Herbert hopes to unlock secrets of the Earth’s past: How have ocean temperatures varied over time? In what ways did these variations affect marine life? What do patterns in ocean temperatures say about the Earth’s past climates?

When he is not piecing together the history of our planet’s climate, Herbert is busy teaching and running Brown’s Department of Geological Sciences.

If you had asked him even during his early years of graduate school, Herbert would not have been able to tell you that he would end up a professor, much less chair of a department. With two professors as parents—a father who taught art history and a mother who taught African anthropology—it seemed almost too obvious to follow in their footsteps.

“It was the last thing I thought I’d end up doing,” said Herbert.

When it came time for college, Herbert chose Yale, where his father taught. It was there that a paleontology course sparked an interest in geology. Then Herbert took an introductory geology course with a professor named Brian Skinner.

“He was a little swashbuckling, and I could imagine him in the field,” Herbert recalled. “On the last class of the semester, he invited everybody into the faculty lounge and we had Swan beer.”

Skinner’s course clinched the deal. Herbert started doing geology research at the Peabody Museum of Natural History at Yale, where, amid one of the largest paleontology collections in the country, he studied 300-million-year-old fossils of tiny, lentil-shaped crustaceans called ostracods. He found that the numbers and types of species in populations of ostracods fluctuated noticeably with changes in the environment over time.

For Herbert, this was an early realization that clues buried in things like rocks, sediments and fossils could hold important information about the Earth’s deep environmental history.

After graduating in 1980, he headed to South Texas to work for the Anaconda Copper Mining Company, then to Dallas to work as an exploration geologist for a startup oil company.

Though he was immersed in the practical side of geology, Herbert found himself regularly visiting the geology library at Southern Methodist University to keep up to date with academic journals. Before long he headed back east, to graduate school at Princeton University.

The man who recruited Herbert to Princeton was a well-known geology veteran named Al Fischer. At the time, Fischer had just drilled a long sediment core from Italy that he believed showed some type of climate cycle.

This was a controversial idea among Fischer’s colleagues. The core dated back to the Cretaceous, a period of relatively warm climate that ran from 145.5 to 65.5 million years ago. There was little evidence to suggest that any structured cycles dominated the Earth’s climate during this time. Besides, most geologists of the day were preoccupied with climate cycles during more extreme events like ice ages.

Herbert was a non-believer himself. He set out to find the fastest way to prove Fischer wrong.

From Fischer, Herbert learned of a computerized technique that researchers in Princeton’s astronomy department were using to locate bright stars on swaths of dark telescope images. He taught himself how to use the technique, hoping that it could detect patterns of lightness and darkness in the sediment core, which he could then correlate to changes in climate.

One early morning, after scanning slides of the sediment core through the night, Herbert finally held the finished product in his hands. “It was absolutely eureka,” he recounted. “I saw emerging, all of a sudden, these patterns, incredibly beautiful, that were exactly the ones Fischer had predicted.”

He and Fischer went on to show that these climate cycles they observed in the sediment core actually aligned with changes in the Earth’s orbit—lending credence to a theory that, at the time, was highly contested.

The clarity of their results and the elegance of their methods landed Herbert his first publication, which appeared in the prestigious journal Nature. For the young graduate student, it was a coup.

The experience taught Herbert two things: scientists can be extraordinarily intuitive, and the right tool can be crucial for spotting an otherwise overlooked pattern.

These years in graduate school convinced Herbert that he wanted to spend his career finding the tools to identify patterns that have shaped the Earth’s climate up to today.

“After grad school,” said Herbert, “I was a nomadic postdoc for a while, just trying to survive.” Following brief spells in Switzerland and Princeton, he landed an assistant professorship at Scripps Institution of Oceanography, where he stayed from 1988 to 1995.

Toward the end of his time there, Herbert began to study alkenones, a group of carbon-containing compounds produced by certain types of marine algae. Earlier research had shown promise that these algae alter the carbon bonds in their alkenones in response to temperature changes in the surrounding water.

Herbert recognized that alkenones could serve as a powerful proxy for studying climate change over geological timescales. By the time he arrived at Brown in 1995, he had decided that they would make up the centerpiece of his research.

Since then, his lab has successfully used alkenones, as well as other indicators of marine biological activity, to study climate histories across various time periods and regions. Most recently, they have reconstructed climate patterns in the Eastern Pacific, where sea surface temperatures undergo variations roughly every five years due to a phenomenon called El Niño.

Research, however, is just one priority for Herbert, who also shows a sincere dedication to his students. He shows up to thesis presentations, attends students’ performances, regularly cooks dinner for his lab members and plays in department softball games.

Interacting with Herbert outside the classroom, his students get to see another side of him. “He’s a totally different person on the field than in the classroom,” said Angel Mojarro, who did his undergraduate thesis with Herbert. “Normally you see him as this huge figure, but on the field he’s just another guy who can’t catch the ball.”

One former student, Alex Kasprak, said that Herbert helped him with his decision to pursue science writing instead of research. If you need to talk to him, “he’ll always give you the time,” said April Martin, who has helped manage Herbert’s lab since 2008. “He’s a genuine article.”

Though Herbert tries to keep personal politics outside the classroom, he hopes to convey through his teaching and his work that, in the context of the Earth’s long climate history, humans are now dominant geological agents in a way that has never occurred in the past and has real implications for the future.

Beyond any societal significance, though, Herbert sees worth in his scientific research simply as an exercise in human curiosity. “I like just doing things that are interesting— solving puzzles—whether or not they help anybody,” he said. “It just is interesting to try to find out something new.”

This piece was originally written for a course at Brown University, “Writing Science” with Cornelia Dean.
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