How Changes in Climate Impacted Ancient Civilizations

Climatologist William D’Andrea of Lamont-Doherty Earth Observatory and his colleagues are plumbing the bottoms of lakes and bays in Norway’s arctic Lofoten Islands to investigate the influence of climate and sea level on the Vikings. Here he hauls up a float that has been moored below a lake’s surface for several years. (Photo: Kevin Krajick)

William D’Andrea is a paleoclimatologist at Columbia University’s Lamont-Doherty Earth Observatory. He explores how climate has changed throughout history using molecular fossils as a natural archive of information about Earth’s past. In particular, he studies fat molecules produced by plants and algae that get preserved in lake sediments. These lipids carry information about the Earth’s climate at the time they were produced and settled to the lake floor. For much of his research, D’Andrea examines how changing climates have historically affected people.

What do you like most about your job?

I love working in the Organic Geochemistry Laboratory at Lamont. People come from all over the world to use our amazing facility and our dynamic group is constantly pushing the envelope and making new discoveries. More generally, science is not only about trying to solve the world’s problems—it’s also fun. It is a real privilege when your job is to pose questions and then try to answer them.

Why do you study climate?

I find it fundamentally interesting to think through how the climate of the Earth has changed through time and what the implications are for ecosystems and how they’ve responded. We now have a more urgent need to understand the full range of how a planet can operate because we are conducting a real-time experiment on the planet where we’re causing it to heat up—causing very drastic changes. We need to be able to anticipate how the planet is going to respond, and more importantly how individual locations will change. There are important decisions that need to be made about planning for the future, and those decisions will be better informed if we can anticipate specific climate impacts. We study the climate of the past as a way of anticipating what it might look like in the future.

D’Andrea (blue cap) pulls up a sediment core from a wetland on Easter Island. (Photo: Andrea Seelenfreund)

What’s a project that you’re currently working on that you’re excited about?

I’m very excited about the work that we’re doing on Easter Island. We’ve collected these beautiful sediment sequences from the wetlands of Easter Island and we’re using organic geochemical techniques to reconstruct past changes in rainfall. We’re looking at the recent past—how the Rapanui people who built the famous moai statues interacted with their ecosystem and how natural climate variability may have impacted their livelihood on the island. And we’re also looking further back—about 30,000 years—to determine drought recurrence on Easter Island and the South Pacific and how that has been connected to larger changes in Earth’s climate system during that time interval. Easter Island is the place where you can get a sediment record from land that’s been keeping track of atmospheric processes in the southeastern Pacific Ocean — it is an important region that also impacts the climate of the rest of the planet. So, the island is extremely important in filling in a gap in our knowledge and I feel very fortunate to be able to study it.

What does paleoclimate have to do with sociology?

Climate is not the only factor in the history of humanity that has had a significant impact on civilizations, but understanding past climate does create a fuller picture of what the people in our human history were experiencing. In addition to studying this on Easter Island, we’re also asking similar questions about the Iron Age Vikings who lived in the Lofoten archipelago in Norway. This area undergoes large changes in climate based on variations in ocean and atmosphere circulation across the Atlantic Ocean. The Norse and their ancestors have lived there for like ten thousand years. They’ve made a living there and they would have had to adapt their lifestyles to many changes. It’s interesting to try to understand what the full range of climate variability was that they were subjected to across that period of time. Not only is this just fundamentally important for understanding the behavior of Earth’s climate system, but hopefully it can also give us awareness and some confidence about our own ability to be adaptable to major changes that we’re going to be experiencing in the future.

If you could have the public take away just one thing from your work, what would you want it to be?

People need to recognize that Earth’s climate system is extremely dynamic and that it can change fast. Many of the climate patterns that we experience now don’t have to be this way. There’s nothing that says this is the way it will always be—climate can change abruptly and in big ways. And we know that because of paleoclimate research.

How do you talk about climate change without terrifying people?

People shouldn’t be terrified, but they should be extremely concerned. “Terrified” implies inaction—scared to the point of paralysis. People should not be paralyzed—that’s a problem. As far as talking to people about global warming without turning them off, I’m lucky in that my research is also interesting on levels that don’t involve global warming. Most people have a natural interest in history—especially human history—so it helps open up the discussion with people about the fact that climate can change and that ancient civilizations that they know about, whether it’s the Mayans, the Vikings, or the Rapanui of Easter Island, that they experienced fundamental climate changes that in some cases may have been too much for their society to handle. And that opens up the conversation about what we are doing to ourselves right now and how we can minimize the worst effects of global warming and avoid being caught by surprise unforeseen changes.

— Nicole deRoberts, Earth Institute

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