Understanding Climate Change

Jeremy Rugenstein studies how the climate has changed since the extinction of the dinosaurs. By looking into the past, the ETH Fellow hopes to gather information about our future climate.

climate change
Climate research with the geologist's hammer: Jeremy Rugenstein. (Picture: Florian Bachmann / ETH Zurich)

Jeremy Rugenstein, a postdoc at ETH Zurich’s Geological Institute, is posing some pressing questions: What will happen to the earth if humans continue releasing carbon dioxide into the atmosphere? How will temperature, precipitation and vegetation change? Will our climate become dryer or more humid?

Fossil soils hold climate data

Instead of focusing on the future, Rugenstein is travelling millions of years into the past, analysing fossil soils in order to uncover information about the prehistoric climate. “By looking into the past – a time when the atmosphere contained much more carbon dioxide – we can understand how the climate behaves with different CO2 concentrations, allowing us to predict our future climate,” he explains.

This research field is known as palaeoclimatology. For his doctoral thesis, the young American researched the prehistoric climate in Central Asia. He demonstrated how we can deduce the amount of precipitation and abundance of vegetation in the past by using mass spectrometric analyses on sedimentary rock. “Plants are a key climate factor, because their water absorption and release determines how much water is available on the earth,” he says.

The geochemist uncovered information about the state of prehistoric vegetation by analysing the fossil soils in which these plants once grew. During root respiration, these plants left behind CO2, which still remains in the soil today in the form of calcium carbonate. This mineral, particularly the carbon and oxygen isotopes it contains, enables Rugenstein to draw conclusions about the past: the carbon reveals how much vegetation grew, and the oxygen reveals the amount and even the origin of rain.

Field work in China, Kazakhstan and Mongolia

The geochemist collected his rock samples in China, Kazakhstan and above all in Mongolia. Known as palaeosols, they are often buried under layers of rock and only accessible at exposed locations such as mountainsides or on the sides of streets.

“Field work is quite difficult,” explains Rugenstein: a long flight, days of driving on dusty roads, hours spent searching for the right rock layers, carefully documenting source locations, breaking off small pieces of rock with the hammer. “Still, I really enjoy fieldwork,” he says. He enjoys desert landscapes, the dryness, and the expansive views: “It feels like home.” This is no surprise: Rugenstein is from Albuquerque, New Mexico, where the desert is at his doorstep.

From a national park to geology

When asked if he had always planned on working in palaeoclimatology, the researcher grinned: “I originally wanted to be a rabbi.” He says this was mainly because of the ethical and philosophical questions he would have confronted on a daily basis. Nor did his upbringing put him on a clear course towards his current field of research either – his father is a physics professor and his mother is a lawyer.

Rugenstein became interested in climate change in high school. His first encounter with geology was in the Cibola National Forest, where at the age of 18, he worked as a park ranger and guide for visitor groups.

It was not until later that he would discover the link between rocks and climate: during his undergraduate studies in the natural sciences in Houston, Texas, he attended a lecture about the link between geology and climate change. “That’s when it became clear that geology could help me answer questions about climate change,” says Rugenstein. “I’ve been a geologist ever since.”

Climate change over the past 65 million years

The 30-year-old researcher is primarily interested in fossil soils from the most recent geological time period, the Cenozoic era, which encompasses the last 65 million years – in other words, from the dinosaurs’ extinction through to the present day. His teaching experience becomes obvious when he begins describing the geological era during which mammals and flowering plants began spreading across wide landmasses.

“It was warmest around 50 million years ago. It’s very likely that there were no landmasses on earth permanently covered in ice. We had palm trees in Antarctica and crocodiles frolicking around Greenland,” says Rugenstein, describing the scenery of that time period. He is particularly interested in why since then, average temperatures have fallen by ten to fifteen degrees Celsius and the carbon dioxide content in the atmosphere has fallen from around 2,000 parts per million to under 400.

Volcanoes and marine organisms

The young scientist, who is clearly pursuing an academic career, is currently focusing on the weathering of rock and understanding how this process is linked to the atmosphere’s CO2 content.

He explains: “In a world without modern, industrialized society, most of the carbon dioxide in the atmosphere comes from volcanoes. However, the majority of it is then removed again by the weathering of rock.” In short, it works as follows: CO2 dissolved in rainwater creates acid and reacts with silicate rock. This produces bicarbonate, which is washed into the ocean in the course of the water cycle. Marine organisms, such as corals, absorb the bicarbonate and use it to build reefs. As a result, the CO2 is taken out of the global carbon cycle for a long time.

New perspectives at ETH

To better understand the role of silicate rock weathering in the carbon cycle, Rugenstein has been carrying out research since January 2017 as an ETH Fellow in the Earth Surface Dynamics group. His work includes puzzling over computer models used to simulate weathering processes.

As a geochemist, Rugenstein has found it enriching to be surrounded by geophysicists in his research group at ETH. He enjoys considering his research questions from different perspectives and bringing his own expertise to other research fields. For this reason, he attaches great importance to connecting with other researchers. With that in mind, he considers the relatively large size of the ETH research group with which he works to be more of a disadvantage: “I’m rarely able to discuss my work with scientists outside of the group.”

A penchant for public transport

Rugenstein really enjoys being in Switzerland. During his free time, he loves hiking in the Alps. As a huge fan of public transport – he didn’t have a car in the USA either – he is enjoying the extensive Swiss transit network: “Here, I can reach almost any hiking trail by train or bus in just a short time.” Only at the very end is he able to think of something that Switzerland is lacking. He grins: “There’s no real desert here.”

Source : ETH Zurich