Linda Sohl Reconstructs Climate Models to Help the Search for Alien Life

Linda Sohl is an earth system scientist at Columbia University’s Center for Climate Systems Research and the NASA Goddard Institute for Space Studies.

You wouldn’t guess it from her quiet voice and modest office, but Linda Sohl has the power to rearrange continents and ice caps. She can look into the future and the deep past, and across the galaxy.

Sohl is an earth system scientist at Columbia University’s Center for Climate Systems Research and the NASA Goddard Institute for Space Studies. Working with fellow scientists and programmers, she reconfigures global climate models to study Earth’s climate past, so that we can better predict its future. She explores the conditions that may have helped to spur the dawn of life on Earth, and simulates the workings of distant planets in hopes of helping to locate other worlds capable of sustaining life.

We chatted with Sohl about the search for habitable planets, the future of our own, and why it’s important to make the world of science more diverse and inclusive.

What are you focusing on right now in your research?

One of the things that we’re doing here is taking a global climate model that has previously been used to focus on future climate change on Earth, and adapting that to other planets. The global climate model, or GCM, has a lot of stuff that’s hardwired into it that’s Earth-specific. And our group has taken a lot of that Earth-specific stuff out. So now we can model climates for other rocky planets.

When I was a kid, I was a huge Star Trek nerd. I loved thinking about the possibility of there being alien forms of life, alien civilizations out there. I have a philosophical problem with thinking that we are the only intelligent species that’s ever existed in the universe, and so doing this work taps in to the fun I always had thinking about, “What else could there be?” For me, this is a really fun and interesting way to explore possible worlds.

I’m also interested in Earth’s history. So another thing I’ve been studying is Snowball Earth ice ages — when the planet has been nearly entirely covered with ice. How do you get into them? How do you get out of them? How severe were they?

How do climate models help to think about life on other planets?

Traditionally, the main criteria for supporting life has been the possibility of having liquid water on the surface of the planet. Water is necessary for life as we know it, and we wanted to see if we can find it elsewhere. So people came at the habitability question from a very simple perspective that measured how far the planet was from its star, and how bright the star was, to calculate the average temperature of the planet; if it’s somewhere between zero and 100 degrees Celsius, it’s possible the planet has liquid water on the surface.

But when you bring an atmosphere into the equation, and the movement of that atmosphere, and the interaction of that atmosphere with possible oceans, it starts to frame your view of habitability rather differently. With atmosphere and ocean involved, you can redistribute heat and moisture on the planet in a way that extends that zone of habitability around a particular star. You can think about planets that might be regionally habitable — maybe, for example, the poles are too cold but the tropics are still warm enough to have liquid water on the surface. This was not something that was really in people’s minds before a few years ago, when modeling groups started bringing GCMs into the picture. We’ve learned there’s a lot more variability out there, in terms of what might be potentially habitable, than we used to think.

How does this habitability work fit in with your research on Earth’s past climate?

When we study the past, the work has two purposes. One is to understand the details of climate patterns and how they are reflected in rock formations and things like that. Exploring climate systems that are not like modern Earth’s can help us to better understand what a future climate might be like.

Then there’s the astrobiological perspective, which asks, What difference does it make to have continents in one configuration versus another? What difference does it make to have ice sheets or not in certain locations? With modeling, we can go back in time and rearrange the continents, or see how water would have been distributed on the moon if it had an atmosphere. It’s an opportunity to exercise some creativity, and sometimes it can lead you to new ways of thinking about stuff — new ideas, new hypotheses for things that you can actually test.

What’s your outlook on Earth’s habitability as global temperatures keep rising?

We have some challenges in trying to understand what’s coming down the pike, but one of the biggest unknowns is what people will do. And I think that if people understand a little more of the science, they can engage in conversations that will determine what their lives and the lives of their children and grandchildren are going to be like. Educate yourself. Watch the TED talks by Gavin Schmidt and Katharine Hayhoe. Check out and, which have a lot of basic information for people to start with.

By being more informed, you’ll be able to assess the ideas and maybe come up with some of your own, and pressure your congresspeople to be engaged. These conversations are not going to be easy, but they don’t have to be scary because you don’t understand what’s being discussed. I encourage people to learn and have hope.

What would you say you are most proud of in your professional career?

For me personally, it’s having arrived at this point considering that when I was younger, I didn’t know if I could do a career in science. I’m a first-generation American. My parents were not familiar with college education and what it might lead you to. The first time I went to college, I studied communications, and I did that because I wasn’t sure I was good enough to do something else, even though I was such a science nerd. It was just that nobody that I grew up with really thought about science as a career, and nobody thought of science as a career for girls, in particular. So overcoming my initial fears and saying, ‘I have to try. I will never forgive myself if I don’t at least try’ — and then coming to a point where my parents have seen me successful as a scientist — that means a lot to me.

Do you have any advice for kids who might feel like you did?

I would say that you should at least give it a shot as an undergrad. Start simple. If it really grabs you, and you start to think that you really don’t want to do anything else, then don’t hold back. Take advantage of every opportunity that may come your way, and go looking for them — go out and make those opportunities happen. If you try it and you don’t like it, there’s no harm in that. For people who do want to go ahead and forge on into graduate school, I would encourage you to be open to a variety of career paths. Because I think it has gotten a lot harder to have a career in academia. Faculty positions at colleges and universities are limited in number and very competitive, and research funding has been relatively flat for a long time — those things make it challenging to have a career in academic science. But if you go into the situation with your eyes open and you still want to give it a shot, then go for it.

We have to get away from the sciences being the domain of just older white men. I think there has been improvement, but I still hear too many stories from all over about women who feel they have to leave science because they’ve run into a mentor who makes life hard for them. It doesn’t have to be through sexual harassment. It could be lack of support. It could be undermining. But if we make an effort to be more inclusive, and we change the culture so that you don’t have to be a hermit in your office with no life in order to be successful, I think we can make the culture of science a healthier one, and a better one for doing better science.

— Sarah Fecht, Earth Institute

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