P2C2: Diagnosing the Dynamics of Past and Future North American Megadroughts

Lead PI: Dr Nathan J. Steiger , Jason E Smerdon

Unit Affiliation: Ocean and Climate Physics, Lamont-Doherty Earth Observatory (LDEO)

March 2019 - March 2022
Global ; Pacific Ocean ; Atlantic Ocean ; North America
Project Type: Research

DESCRIPTION: This project aims to explore the cause and occurrence of multi-decadal droughts, broadly characterized as megadroughts. Megadroughts have the potential to critically affect society through disruptions involving agricultural production, food security, municipal water supplies, and ecosystem services.

The possibility that they may occur in the future is suggested by two lines of evidence: (1) they have occurred in North America during the past 2,000 years and several megadroughts even clustered together in time during the early Middle Ages; and (2) climate model simulations suggest that increasing global temperatures will progressively increase the likelihood of a megadrought in this century.

Despite the awareness of megadrought recurrence, the causes of these droughts are inadequately understood because of a lack of long-term information about climate dynamics that is physically consistent with reconstructions of past megadroughts. This project seeks to address this apparent shortcoming by producing a novel data-assimilation-based reconstruction of global hydroclimate that also includes a reconstruction of dynamical variables.

Specifically, dynamical characterizations of past megadroughts will be used to test prominent hypotheses about the causes of megadroughts in the American Southwest, the Central Plains, and Mesoamerica thereby helping diagnose their causes in a physically consistent and self-contained framework. Theories will be tested that hypothesize involvement by Pacific and Atlantic sea surface temperatures, shifts in the Intertropical Convergence Zone and midlatitude storm tracks, and exogenous forcing. The potential dynamic causes and forcing of megadrought clustering during the early Medieval period will also be evaluated. The megadrought dynamical characterizations will subsequently be used to benchmark climate and to estimate the potential risk of megadroughts in the 21st century.

The potential Broader Impacts include greater understanding of megadroughts and their potential societal impact, support of an early career scientist, and involvement of undergraduates in the research.


National Science Foundation (NSF)






Oceanic Drivers of Widespread Summer Droughts in the United States Over the Common Era, https://doi.org/10.1029/2019GL082838; Oceanic and radiative forcing of medieval megadroughts in the American Southwest, https://doi.org/10.1126/sciadv.aax0087

No evidence for globally coherent warm and cold periods over the preindustrial Common Era, https://doi.org/10.1038/s41586-019-1401-2


food security global temperature agriculture megadrought water sea surface temperature


Modeling and Adapting to Future Climate