Brian Schubert, University of Louisiana at Lafayette – Using Fossil Plants to Measure Climate Change

What can fossils teach us about the future of climate change?

Brian Schubert, associate professor in the school of geosciences at the University of Louisiana at Lafayette, digs in to look ahead.

I have been at the University of Louisiana at Lafayette since 2013 and currently serve as the Coordinator for the Geology BS and MS programs, as well as an interdisciplinary PhD program in Earth and Energy Sciences.  The University is the leading institution within the University of Louisiana System, and the School of Geosciences offers five academic degree programs. The School includes 13 faculty members, four full time instructors, a research scientist, and approximately 200 total undergraduate majors and 85 graduate students.

​Within the Carnegie classification, UL Lafayette is designated as a Research University (high research activity)(RU/H). Located mid-way between New Orleans and Houston, Lafayette is a city of >126,000 people, and is one of Louisiana’s fastest growing areas and the hub of numerous cultural festivals and activities.

Using Fossil Plants to Measure Climate Change

We learn as children that all plants require water and carbon dioxide to grow. The water comes from rain or melted snow that infiltrates into the earth and enters the plant through the roots, while the carbon dioxide diffuses through pores into the plant’s leaves. Every plant on planet Earth uses these two ingredients to form new compounds via photosynthesis. When the plant dies, a fortunate few are buried beneath layers of silt and sand, removed from the ravages of oxygenic decomposition, and preserved in the geologic record. As a geochemist, my job is to analyze the chemical remains of these fossilized photosynthesizers to answer questions like, “When was the last time carbon dioxide levels were as high as today?” and “How will global warming affect precipitation patterns across the planet?”

To answer these questions we study the products of photosynthesis that had been locked away for millions of years within fossilized plant remains. We do this using a specialized piece of equipment called an isotope ratio mass spectrometer. This machine has a giant magnet that separates and then counts individual molecules freed from within the fossils by first heating to over 1000 ^oC. These liberated molecules contains the exact same carbon and oxygen atoms that once made up the carbon dioxide and water that were combined many millions of years ago by the plants’ photosynthetic machinery. Our work has shown that these compounds provide a chemical fingerprint of the amount of rainfall that fell over the forest and the amount of carbon dioxide available for photosynthesis many eons ago. Our end result is a veritable weather report of changing climate across millions of years of Earth history that implicates changing carbon dioxide concentrations as the primary perpetrator for perturbing Earth’s climate, past and present.