Donald T. Rodbell, the John and Jane World Professor of Geosciences at Union College, is the lead author of a paper published in Nature this July that shows that greenhouse gasses have brought the tropics into synchronous climate change with glaciers in the polar regions over the last 700,000 years, according to a Union College News Article. Nature is the world’s leading journal of peer-reviewed scientific research.
This paper is based on data from fieldwork conducted in 2015, when Rodbell led a team of 30 scientists who collected a 100-meter deep sediment core from beneath Lake Junin, located in the Peruvian Andes. This was the first continuous record of tropical glaciation over the past 700,000 years. This decade-long research project was funded by the International Continental Scientific Drilling Program and the U.S. National Science Foundation. Other institutions involved include the University of Pittsburgh, Massachusetts Institute of Technology, The University of Florida, Oregon State University, and the University of Minnesota.
The paper shows that the record of glacial variations in the Andes is extremely similar to glacial variations at higher latitudes over a period of almost 700,000 years. The team used radiocarbon dating, uranium-thorium dating and geomagnetic measurements to establish that material in the core spans 680,000 years, according to a Nature news article. Rodbell and colleagues attributed the general similarities between high- and low-latitude glacier expansions to factors related to the growth of the large northern ice sheets and the global impacts of reduced greenhouse gas concentrations. They suggested that some characteristics of the Lake Junin record arose from expansions of northern ice sheets that were affected by the redistribution of sunlight off the Earth’s surface from fluctuations in its axis tilt. It is clear from this study that any hypothesis to explain what drove ice-age climate cycles should account for the extreme similarity between glacial periods in the tropical Andes and in both polar hemispheres.