EMES Colloquium Speaker – Jason Smerdon, October 21, 2026

Attend in person to receive CLE credit

Our story begins more than a thousand years ago in northwestern New Mexico among the thriving pueblos of Chaco Canyon.  Beginning in about 900 CE, Chaco Canyon was the site of a thriving Ancestral Puebloan culture that, among other things, would cut sandstone blocks and huge timbers to build the largest structures in North America until the 19th century.  Beginning around 1130 CE, however, the Chaco Canyon settlement was progressively abandoned, a response that is thought to have been triggered by one of several multi-decade droughts, or megadroughts, that would bedevil the American Southwest during the Medieval period.  Little did the Ancestral Puebloans know that more than a millennium later their fate would be the subject of fascination and alarm when megadrought would return to the Southwest, this time supercharged by human-caused climate change.  But how do we know about climate during the time of the Ancestral Puebloans and what does it tell us about today and our future?  The answer is a complicated one that connects global scientific efforts to sample trees, corals, cave deposits, ice cores and more, to characterize remote conditions in the Pacific and Atlantic Oceans, to simulate climate on supercomputers, and to apply complicated mathematics aimed as drawing connections between these various sources of disparate information.  These efforts have allowed us to characterize climate during the bustling heyday in Chaco Canyon, as well as identify the current 26-year megadrought in the Southwest to be the most severe since at least the time of the Ancestral Puebloans.  These efforts also have led us to understand the causes of megadroughts in the past and present, which has broadened our understanding of how Southwestern megadroughts are part of a pan-Pacific pattern of hydroclimate anomalies that are driven by decadal variability across the Pacific Ocean.  The implication for the future is that megadroughts will come and go, but they will be progressively exacerbated by continued warming, making them more severe, more frequent, and more widespread in places like Chaco Canyon and the broader American Southwest.