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Getting to the Core of Climate Change


Jean Lynch-Stieglitz was introduced early to the rigors of scientific fieldwork, globetrotting with her archaeologist father, her mom, and sisters to Peru, Ecuador, and Chile.

“It was definitely a different way to grow up. I first went when I was 2, until I was 12 or 13. Even when I was very small, I was wielding a toothbrush, washing off artifacts,” said Lynch-Stieglitz, a professor at the School of Earth and Atmospheric Sciences and a climate change expert at the Georgia Institute of Technology in Atlanta.

The self-described “bookish kid” who sailed through math and science classes was torn between a career in physics and geology. So while earning degrees in both fields, she found the problems in geology and earth sciences more compelling – and familiar considering how her father explained geological formations on their family travels – as well as a more likely path toward making a difference by focusing on climate and oceanography.

She has made her mark in both teaching and research. Lynch-Stieglitz was the first woman professor in the Department of Earth and Environmental Sciences at Columbia University. And her paleoclimatology research is unearthing clues to the behavior of our oceans and climate over the last 100,000 years; knowledge that is lending insight into contemporary climate issues.  

The treasure that Lynch-Stieglitz is searching for is a single-celled organism called foraminifera. When they die, their chalky shells form thick ocean-floor sediments. It is within those layers that you have a history going back hundreds of thousands of years.

“The mud at the bottom of the ocean is almost entirely [foraminifera],” she said. “It’s not like hunting for dinosaurs. They are just there!”

Retrieving the core samples that provide much of this insight can be a hit-or-miss endeavor since these scientific secrets are buried sometimes miles below the ocean surface. Ideally, research teams will look for soft, fluffy mud where their tools – imagine a PVC sewer pipe with a lead weight attached – can easily penetrate the ocean bottom and retrieve core samples. The research cruises to gather these core samples typically last about a month and they often surprise scientists.

“You really don't know what you are going to find until you get out there. And this is particularly true for those of us who work in ocean sediments,” Lynch-Stieglitz said. “Part of that is because much of the seafloor has not been mapped in detail. Plans have to change. And sometimes it can be a little stressful.”

“It’s like playing a long drawn-out video game, where you are just constantly having to make decisions, and figure out how you are going to change things to get things done. In the end, when you get even some of what you wanted, it’s very rewarding,” she said.

Back in her lab at Georgia Tech, the professor uses an accelerator mass spectrometer to look at different isotopes of oxygen and carbon in these calcium carbonate shells. It’s one of the most effective techniques for determining ocean and climate conditions in the distant past. Different clues come from the planktic foraminifera of the upper ocean and from the bottom dwelling benthic foraminifera. Oxygen isotopes reveal the temperature and salinity when the foraminifera were alive. Carbon isotopes reveal how carbon has moved through the ocean atmosphere.

 Collaboration with other scientists is key in the more complex picture of climate analysis.

“One of our roles is to provide a creative spark to climate and ocean sciences. Another role is a little bit more direct, and that is to provide data that can validate whether climate models are working correctly,” she said. 

She probes different oceans for different clues. She looks to the North Atlantic circulation to determine the net transport of heat from the Southern Hemisphere into the Northern Hemisphere, while the Southern Ocean surrounding Antarctica remains rich with information.

“The Southern Ocean has an outsized influence on the amount of C02 that is in the atmosphere, as opposed to the amount that is stored in the ocean. So if we want to understand why there was less C02 in the atmosphere during the last ice age, then we need to understand circulation in the Southern Ocean,” she said.

She says that starting in the early 1980s, paleoclimate experts started to get the idea that the ocean circulation in the North Atlantic changed. 

Lynch-Stieglitz was chosen as an AAAS Fellow for providing details of the oceans' interaction with today’s climate change by understanding ocean circulation events during ice ages.

“We can’t directly translate what we do into a prediction for the future. But I think we do play a very important role. One role we play is to introduce new ideas about parts of the climate system that might be particularly sensitive to change; what parts of the climate system have changed in the past,” she said.

She realizes that while many of her students may not pursue careers in the geosciences, the goal is to teach them to think like scientists. That’s especially true when dealing with the sometimes politically charged aspects of climate research.

“I am hoping they will have the tools to read a newspaper article five years from now, and say, ‘That sounds reasonable,' 'That makes physical sense' or, 'That sounds a little bit wacko, let me look into this.’ I want them to have the tools to critically think about the world around them,” she said.

And that outreach goes beyond campus to spread the basics of an understanding not just of climate change, but all science. In her interactions with a sometimes-skeptical public, she stresses that our understanding of C02 and other greenhouse gases is something scientists have understood for many, many years.

“Some details about climate change – exactly how warm, exactly how fast, how is precipitation going to change in this particular location – those details are still being worked out,” she said


Marsha Walton

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