Climate scientist combines research and teaching into ‘perfect storm’ of discovery

This fall, Hurricanes Helene and Milton served as painful reminders of how climate change is fueling extreme weather, supplying warmer ocean waters and warmer air temperatures that lead to wetter, stronger tropical cyclones.

It’s not just hurricanes, however, that are breaking rainfall records and devastating communities. Storm systems in all parts of the country, including the Midwest, are pushing the bounds of recorded weather history.

Indiana University Bloomington climate scientist Travis O’Brien is at the forefront of exploring this trend. An assistant professor in the College of Arts and Sciences’ Department of Earth and Atmospheric Sciences, O’Brien uses numerical models, data analysis and fundamental theory to study the Earth’s climate system and untangle the factors that feed extreme weather.

What themes does your research explore?

I’m really interested in what drives changes in weather from year to year, decade to decade, and even longer timescales. And when I say what drives changes, to some degree that’s anthropogenic, or human caused.

Climate change is obviously a factor in the long term, but in the short term there’s a lot of natural variability in weather that still needs more research. We could probably make better predictions about year-to-year changes in rainfall, for example, if we had a better handle on the factors that influence weather.

Broadly, the research that I do uses observational data and models, such as global and regional climate models, to disentangle all these things.

What’s one of your current research focuses?

One question I’m exploring is how often different types of weather phenomena occur in the same vicinity. For example, how often does an atmospheric river occur alongside a mesoscale convective system, which is a large organization of thunderstorms. There have been a few studies on specific pairings of weather phenomena or on specific regions, but we’re seeking to do a global study and look at several different weather phenomena.

A relatively recent example of this is the floods that took place in Bloomington in June 2021. Those were the result of an atmospheric river and a mesoscale convective system all happening in the same system.

That sort of co-occurrence is one of the reasons I’m really interested in this question. Do you always get these really big precipitation events when they occur together, or was it random chance that that event happened to be so strong?

What sparked your interest in atmospheric rivers?

Atmospheric rivers are long, narrow corridors of water vapor transport. When they form, they typically bring a lot of rain. I experienced them a lot while living in coastal California. When I moved to Indiana and started looking at meteorology and satellite imagery, I kept seeing them, but I wasn’t seeing people talk about them too much.

This year, I co-authored a paper in Geophysical Research Letters that establishes how atmospheric rivers occur in the eastern United States. They’re actually quite common here as well.

Because of the amount of rain they bring, the question a lot of people are interested in is, “Are there going to be more atmospheric rivers or fewer down the road?” That actually depends on how you define them, for reasons my colleagues and I are working to understand.

Some detection methods predict no changes in atmospheric rivers in a future climate; some predict a very strong increase. There’s still debates on whether their preferred locations might shift with climate change.

Why did you decide to pursue a research career at IU?

When I joined the Bloomington faculty in 2019, I thought it was a really cool opportunity to be part of a young and growing atmospheric science program, along with being a part of the Environmental Resilience Institute. It seemed like a place where I might really be at the beginning of something in terms of developing an atmosphere and climate adaptation research program.

On top of that, IU offers free supercomputing resources to faculty. A lot of what I do is modeling, which requires lots of computing, so that was definitely a draw.

How do you involve students in your research?

CORDEX—Coordinated Regional Climate Downscaling Experiment—is a regional climate modeling effort that takes global climate model outputs and downscales them so they’re more usable for people making decisions at a national or state level. I thought this was a good opportunity to bring in some young scientists through the College of Arts and Science’s Arts and Sciences Undergraduate Research Experience program.

Last spring, I had two students actually running simulations of that June 2021 storm. Our idea is to simulate a version of the event where temperature and humidity reflect a climate consistent with no human-caused global warming and then compare it to a version of the event in a climate with the level of greenhouse gases we expect 50 years from now. That type of experiment could be really informative for people making decisions about stormwater management or emergency preparedness at the community level.

The combination of the particular model that I’m using and the free availability of supercomputing resources is allowing students who don’t have any scientific computing experience to get a model like this up and running pretty quickly.

What excites you about the work you’re doing?

I love the group of people that I work around. At this point, I have collaborative research with all of the atmospheric science faculty in the department, and I’ve also started to work with geoscientists in the department as well.

It is exciting to be able to combine teaching and research—to actually have my research interests be part of students’ learning experience—and to have students be able to contribute to real science questions. This type of experiential learning is a really valuable complement to classroom learning.