Dr. Rachel Lupien, Paleoclimatologist

Rachel working in the organic geochemistry lab.

What is your favorite aspect of being a scientist? How did you become interested in science?

My favorite part about being a scientist is learning something new every day. We get to ask and answer questions; some experiments are very large and involve many people and many years, and others are accomplished just by graphing our data in a new way. We also get to learn from our friends and colleagues, and from papers, talks, and lessons of the community. I really like my job because it is a great mix of field, lab, and computer work. I’m never bored, although some tasks are definitely tougher for me than others. Field work, conferences, and short courses have brought me all over the world, and this sort of travel is so exciting.

I’ve always looked for how to apply the things I’ve learned. I was good at math in school, but to me, applying those math skills to scientific questions was always more interesting. I thought I wanted to be a chemistry major at the beginning of college, but the Earth sciences incorporated the application of math, chemistry, physics, and biology to topics like volcanoes and earthquakes and climate change. I then studied geology, really digging into how the Earth moved over billions of years, but now I have further applied my scientific background to a topic that I find is absolutely crucial for us as a society to understand: climate change.

Rachel in Norway, where she was taking a sediment core from a lake.

What do you do?

I study the natural variations of climate in Africa over many millions of years to understand how environmental change drove human evolution. I analyze rainfall, plants, and other climate parameters by studying fossil molecules that are transported from land, buried, and accumulated over time in lake and ocean sediment. I then quantify the climate patterns over different time scales, and attempt to understand the relationship between our human ancestors (hominins) and their environment. I also make links with global climate changes to understand the sensitivity of the African environment to changes in solar radiation, greenhouse gases, ocean circulation and temperatures, and glacial-interglacial cycles. The past is the key to the future, and these connections will help us understand how this historically under-studied continent will respond to current and future global warming.

What are your data, and how do you obtain them?

Rachel holding the real skull of a baby ape, named Nyanzapithecus alesi. This fossil is 13 million years old!

I am an organic geochemist working mainly with leaf wax biomarkers. These waxes (the shiny coating) are produced by plants to protect them from excess evaporation and physical damage. Eventually the waxes are transported to the bottom of a watershed, like a lake or the ocean, and preserved in the sediment. They are preserved because the waxes are comprised of long organic molecules, meaning a bunch of carbon and hydrogen atoms arranged in a row, which makes them resilient to weathering or degradation. Over time the waxes are preserved along with the lake/ocean sediment as it accumulates, and we go and take cores from these archives. We split open the sediment cores and do a long series of geochemical extractions in the organics lab. Finally, I measure the isotopes of both the hydrogen and carbon atoms in the leaf waxes, which are proxies for precipitation amount and plant type, respectively. I then plot these isotope data versus depth or age to understand how the climate changed over time, and do quantitative analyses to understand the cycles, shifts, and amplitudes of variability in the climate system over million-year, millennial, and centennial time scales.

How does your research contribute to the understanding of climate change and evolution?

I study and teach about past, current, and future climate change and the effects of climate change on evolution. Our human ancestors (and other animals) lived and depended on their environment, which was likely driven by natural oscillations in the climate system. By understanding environmental responses to climate, we can test various theories about the link between ecosystems and human evolution. This work gives us a better idea not only of how resources (habitat, food, land use) will change with future global warming, but also what characteristics of climate change human populations are likely to respond to. The rate at which the Earth is currently warming and changing is very important to understand when thinking about the human response, and reconstructing climate change in the past on these shorter time scales is something that I’m interested in focusing on in the future.

What advice do you have for aspiring scientists?

Rachel in Kenya, teaching a field course.

Disseminating your scientific findings is so important. If you put in a lot of work to your research, but can’t let the world know what you found, it’s not helping the public to its maximum potential. I was always such a math/science kid, even through college, and I didn’t realize the importance of being a creative, focused, clear, interesting writer. My advice for aspiring scientists would be to read and write often and to work on these as skills. No matter what scientific profession you end up in, including academia and industry, you will need to write succinctly for a wide audience. But no fear! I used to think I was a terrible writer and I really didn’t enjoy it, but it is something that I’ve practiced and improved upon over time.

Rachel is a postdoctoral research scientist at Lamont-Doherty Earth Observatory. To learn more about her and her research, follow her on Twitter @loopdlupien or visit her website here.


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