Alumni profile: Hannah Nesser, Ph.D. '23

When Hannah Nesser was applying to graduate school, she asked a critical question: how can I really make an impact on climate change? Was it better to study environmental policy, or do research in a lab? Could she do the most good by working in the field, or would computer modeling be the best path?

“I just wanted to chip away at whatever part of the problem I could,” said Nesser, Ph.D. '23. “I really loved math, so a data analysis-centric group was really exciting to me.”

Nesser found what she was looking for in the Atmospheric Chemistry Modeling Group, led by Daniel Jacob, Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS). Jacob became Nesser’s Ph.D. advisor in environmental science and engineering, helping her develop data analysis and computer modeling skills as she researched carbon emissions and air quality.

Immediately after graduating, Nesser joined NASA’s Jet Propulsion Lab as a postdoctoral fellow in the Carbon Cycle and Ecosystems group. She now uses data from NASA satellites to monitor and quantify carbon dioxide emissions using the same modeling tools she developed at SEAS.

“I use satellite observations of greenhouse gases to try to tell us something about greenhouse gas fluxes, whether it’s methane emissions or carbon dioxide uptake or release,” she said. “I really enjoy that problem, and I really enjoy having the opportunity to continue to work on it from the perspective of carbon dioxide, which is a longer-lived gas that has fascinating mechanics when it comes to uptake and release. Forests breathe in and they breathe out. I’ve enjoyed working on this problem within this mathematical framework.”

Though always interested in the environment, Nesser didn’t start to consider it as a career until deep into her undergraduate studies at Yale. An environmental engineering major, Nesser spent her senior year working with her thesis advisor to develop low-cost portable air quality sensors. In the midst of that project, Nesser told her advisor that she wanted to pursue environmental engineering as a career.

“He said I needed to get a Ph.D., and provided a list of people I might want to work with,” she said. “I had no clue how the academic world worked at that time. I’d never contemplated doing a Ph.D. So after graduating, I took a year to put my application together.”

As Nesser worked through the application process, she used her year away from academia to immerse herself more in policy work, working as a deputy data director for the Iowa Democratic Party and then as legislative assistant for the Union of Concerned Scientists. But she knew she’d eventually return to research, and it was just a question of the type.

“In the end, it was between a field research program, where I would’ve been flying around in a plane going through smoke plumes, and Daniel Jacob’s group at Harvard,” she said. “Some of it came down to the types of problems I was going to work on, and some of it came down to how in a modeling group, you’re working from a computer. That meant I could go home to Minnesota and see my family, work from home and be present for my family in a way that really appealed to me.”

Nesser had no way to know it, but the appeal of working from home would come to fruition, as the campus temporarily closed in 2020 due to the COVID-19 pandemic. She found a way to not only continue her work remotely but thrive: As an atmospheric chemistry teaching fellow, she was nominated by her Spring 2020 students for a Special Commendation for Extraordinary Teaching in Extraordinary Times.

Along with teaching, Nesser also became an advocate for diversifying the environmental science student body. She co-founded and lead the Diversity, Inclusion and Belonging (DIB) subgroup of the Harvard Atmospheric Chemistry Modeling Group, was a graduate representative of the Harvard Earth and Planetary Sciences and Environmental Science and Engineering DIB Committee and co-lead the Harvard Earth and Planetary Sciences Unlearning Racism in Geoscience pod. She also served 16 months as co-president of the Harvard Graduate Environmental Action Team and volunteered with the Harvard Emmett Environmental Law and Policy Clinic.

“I’m generally interested in anything we can do to make these spaces more inclusive,” she said. “The more people that are working on this problem, the better chance we have to do something about it.”

Nesser still has over a year left in her fellowship, so she doesn’t yet have to make any decisions about what comes next. But if there’s a line between scientific research and science policy, she knows exactly where she wants to be: doing research, but research whose data directly informs policy makers who can make an impact on air quality and climate change.

“I’m constantly surprised by where this field has gone, and all the opportunities I’ve been lucky enough to stumble upon,” she said. “I’ve had lots of opportunities to collaborate with people who are trying to chip away at the problem of climate change. It’s not just about publishing papers – it’s about what we can actually do to fix this problem.”