Ancient Lake Sediment Reveals Millennia of Climate History and Pacing for Climate Change Now

Sediment core in Northwestern University’s GeoCAL Lab. Photo by Jamie Dickman.

How do you travel back in time? If you asked a Ph.D. student researching in Northwestern University's Geoperspectives on Climate and Life Laboratory, they would probably answer, "dirt."

"The more sediment that we recover, the further back in time we can go," said Pete Puleo, a 4th year Ph.D. student with GeoCAL. These climate researchers venture to isolated landscapes to extract 14,000-year-old sediment samples from lakes and study them as part of an international research effort to create a fuller picture of the Earth's climate history. 

Revealing climate history allows scientists to utilize it to assess current climate change impacts accelerating due to human activities, such as ice melt.

The Earth's atmosphere has changed drastically, from hot spells to ice ages over thousands of years. Even between these ancient extremes, recent climate change has no comparison. "There's no other analogous time in history that we see this level of climate warming, but there are similar times in the last two and a half million years," said Mia Tuccillo, a 3rd Year Ph.D. student. 

By looking at those similar high-temperature periods in history, researchers such as Puleo and Tuccillo can reimagine past environmental conditions, including weather trends, water flow, plant growth, temperature, and glacier movement.

Tuccillo said that identifying times with similar temperatures allows scientists to answer the leading question, "if it was this much warmer at this time period and we're approaching that warm, what can we predict about what might happen in this area in the future?" 

But previous warmings never exceeded 1-degree Centigrade across those 2.5 million years. 

To better understand today's atmospheric processes, like many things, these researchers look to history. However, some places and their people are historically more vulnerable than others regarding climate change's effects. For example, the Arctic has been warming nearly four times faster than the global average over the past forty years.

Sediment cores contain well-preserved plant matter that can be extracted and analyzed. Mia Tuccillo specifically studies the chemical composition of leaf pigments to determine climate history. 

"I'm trying to focus my attention on places that are warming quickly and places that are neglected in the world," Tuccillo said. Not every part of the world is studied equally, either. There are significant gaps in data in places such as Africa, Russia, and the Arctic–likely a function of Western-based research and funding. 

She cited Arctic greening as a primary climate change-driven phenomenon destabilizing Northern environments such as Greenland, her specific area of research focus. Arctic greening refers to an increase in plant life in the Northern hemisphere following permafrost melt, which destroys ecosystems where organisms evolved to survive in ice cover.

The ecosystem isn't the only part of the Arctic damaged by climate change. "There are a lot of indigenous people that have been historically excluded from a lot of narratives," Tuccillo said. "To people whose traditions rely on ice cover and aquatic organisms that live in really cold areas in the ocean, this arctic greening destabilizes their traditions, communities, and culture."

Bailey Nash, a 2nd year Ph.D. student, said the team also stresses cultural sharing. "We're not just trying to get familiar with the environment, the plants, and the climate history, but also people, and I think that science is moving in that direction."