Partnered with the National Center for Atmospheric Research




Our work focuses on decadal-multidecadal drought variability – a scale neither well constrained by observations nor well represented in models. We focus on key vulnerable regions, where natural variability and anthropogenic change combine to amplify the risk of prolonged, severe drought with large consequences: southwestern North America (US and Mexico), Australia, Amazonia, South Asia, the Caribbean, and West Africa/Sahel. Our strategy takes advantage of several unique observational, model and stakeholder resources: (1) an unprecedented ensemble of simulations of the past millennium from a state-of-the-art Earth System Model (NCAR CESM1.0; in addition to the CMIP5 archive); (2) an expanding set of published and emerging paleoclimate datasets from multiple proxies that reveal long observational histories of decadal-multidecadal hydroclimate variability; (3) a longstanding network of stakeholders and collaborators in the southwestern US and Mexico with whom we can develop best practices in applying drought risk estimates to real-world problems across a broad social context; and (4) a long history of working on drought variability and stakeholder-driven science in other drought-prone regions worldwide. Our research strategy addresses the following questions: What is the observed nature of decadal-multidecadal drought in vulnerable regions of the globe? How well do the NCAR ESM and other CMIP5 models simulate observed decadal-multidecadal drought? How do we combine observational and model-based perspectives to quantify estimates of prolonged drought risk in key regions over the next few decades? How can knowledge about drought risk be optimized for use by diverse stakeholder communities in developed and developing countries?


Drought is among the most ruinous of natural disasters and is expected to become increasingly prevalent in a warming world. Superimposed on anthropogenically-forced changes will be natural decadal to multidecadal hydroclimatic variability that is poorly quantified for most of the globe, larger than the forced changes for the near term, and incompletely represented in coupled models. Among the greatest challenges of decadal prediction are the quantification of prolonged drought risk in vulnerable regions and the integration of knowledge about this risk into the decision-making processes of the many resource managers and other stakeholders who deal with drought. We are overcoming these two challenges through interdisciplinary collaboration between leading climate institutions (NCAR and the University of Arizona) with exceptional strengths in the integration of climate modeling, knowledge about climate variability, and stakeholder partnerships.

Team Members

Bette Otto-Bliesner
Principal Investigator

Bette Otto-Bliesner is a Senior Scientist at the National Center for Atmospheric Research in Boulder, Colorado, and serves as head of their Paleoclimate Modeling Program. Her research focuses on using computer-based models of Earth's climate system to investigate past climate change and climate variability across a wide range of time scales, including the Last Millennium, glacial-interglacial cycles, and warm periods during the Pliocene and Cretaceous. She is a member of the Scientific Steering Committee for the Paleoclimate Modeling Intercomparison Project, coordinating international climate model experiments addressing past climate change relevant to understanding future change. She has been involved in the Intergovernmental Panel on Climate Change reports and has served on national and international committees for the US National Research Council and IGBP (Past Global Changes).

Jonathan T. Overpeck ("Peck")
Principal Investigator

Dr. Overpeck is a Regents Professor of Geosciences and Atmospheric Sciences at the University of Arizona.  His research focuses on global change dynamics, with a major component aimed at understanding how and why key climate systems vary on timescales longer than seasons and years. Current work focuses on the Asian and West African Monsoon systems, tropical Atlantic variability, and El Niño-Southern Oscillation dynamics.  Ongoing projects include the use of lake sediments for paleoenvironmental reconstruction, with special emphasis on the occurance of megadrougths over the last millennium. In addition, Dr. Overpeck is using paleoenvironmental data to understand linkages between climate and vegetation change, and to assess how the terrestrial biosphere may be impacted by future climate change and human activity.

Julie Cole
Co-Principal Investigator

Julia Cole is a Professor of Geosciences and Atmospheric Sciences at the University of Arizona. She is an interdisciplinary paleoenvironmental scientist whose research emphasizes climate and environmental change on human time scales, in systems with large societal impact. She uses paleodata to provide a deeper perspective on phenomena such as El Niño, drought, reef environments, and monsoon systems. An important theme of her group's work is how paleodata can refine our insights into potential future changes, for example by improving climate model assessment and documenting the full range of recent observed variability. Science communication plays an important part in her work: she has held several competitive fellowships focused on interdisciplinary science communication and policy, and includes environmental science communication in her graduate teaching. She has served on several National Research Council committees and participated in IPCC assessments.

Diana Liverman
Co-Principal Investigator

Diana Liverman is a Professor of Geography and Development and co-director of the Institute of the Environment at the University of Arizona.  Her research focuses on the human dimensions of global environmental change including climate vulnerability and adaptation, climate change and food systems, and climate governance, especially in the Americas.  She has served on national and international committees for the US National Research Council (e.g. America’s Climate Choices, Human Dimensions), the Inter American Institute for Global Change Research (IAI), and ICSU (Global Environmental Change and Food Systems, Earth Systems Governance, Future Earth).  She is committed to improving interdisciplinary research through the participation of social scientists and stakeholders.

Toby Ault

Toby Ault is an Assistant Professor in the Department of Earth and Atmospheric Sciences whose research has coalesced around three areas of inquiry related to emergent climate risks: (1) estimating the risk of prolonged drought under climate change; (2) understanding the dynamics of seasonality, particularly spring; and (3) characterizing variations in the Tropical Pacific on timescales of decades to centuries, and their influence on global climate. His methods entail data synthesis from observational sources as well as numerical and statistical modeling. The nature of his work is therefore highly interdisciplinary, affording him the opportunity to collaborate closely not only with climate scientists and modelers, but with colleagues in many other disciplines, including geography, paleoclimatology, and ecology.

John Fasullo

John Fasullo is a project scientist at the National Center for Atmospheric Research in Boulder, Colorado. He studies climate change and variability using both observations and models to address a range of questions with societal relevance. His work includes recent studies on our ability to monitor and understand changes in the global water cycle, and narrow uncertainties in the climate system’s response to elevated greenhouse gases. He  received his Ph.D. from the University of Colorado and was awarded the 2015 Journal of Climate Editor’s Award.

Sam Stevenson

Samantha Stevenson studies tropical ocean variability and its impacts on drought-prone regions worldwide, with particular emphasis on evaluating representation of oceanic and hydroclimate variability in climate models using paleoclimate proxy information. Her PhD work focused on the El Nino/Southern Oscillation (ENSO) response to climate change, and as a postdoctoral researcher she developed new methods to estimate ENSO variability from fossil coral records. As part of the EaSM project, she is using Last Millennium model simulations to better determine how the tropical Pacific has contributed to sustained droughts in the Southwestern US and other arid regions.

Sneha Balakrishnan
Graduate Student

Sneha Balakrishnan is a PhD student at the School of Geography and Development, University of Arizona. She has a Masters degree in Environmental Studies and has in the past worked as an Associate Fellow for The Energy & Resources Institute (TERI) in New Delhi, India. Her research mainly focuses on stakeholder engagement processes in climate change adaptation planning. She has experience in implementing participatory methods to capture stakeholder perceptions and has also engaged in research that aims to convert complex scientific information into more comprehensible forms for communication to different user groups.  

Nicollette Buckle
Graduate Student

Nicollette Buckle is pursuing a Masters degree in Geosciences at the University of Arizona. She is currently reconstructing droughts in the Amazon basin using lake sediments from the Ecuadorian lowlands. She also uses climate model output to explore the mechanisms that produce sustained tropical droughts. She hopes that her research will increase understanding of long-term variability of drought in the tropics.

Melissa Harrington
Graduate Student

Melissa Harrington is a M.S. candidate in the Geosciences Department at the University of Arizona. Her research focuses on reconstructing drought in the Southwest U.S. using cave deposits. In particular, she is working to develop a new measure of drought using trace elements in stalagmites and drip waters from southern Arizona caves. She is also using climate model data in her analysis. She hopes that her work will contribute to a better understanding of drought in semiarid regions.

Garrison Loope
Graduate Student

Garrison Loope is a PhD student at the University of Arizona studying drought in South Asia.  He uses paleoclimate data, climate models, and observations to look at the frequency of severe droughts and the mechanisms that cause them.  He collects lake sediments from Nepal to reconstruct drought and lake level history over the last thousand years. His research also uses the existing wealth of paleoclimate data from South Asia including ice cores, tree rings, cave deposits, and marine sediments.

Luke Parsons
Graduate Student

Luke Parsons is a Geosciences PhD candidate at the University of Arizona. He studies the duration and frequency of drought in South America and other drought-prone regions around the world. His research focuses on reconstructing past dry periods using lake sediments. Luke also tests the ability of climate models to accurately reproduce past rainfall. He hopes his work will help local and international officials, as well as on-the-ground resource managers, make better-informed decisions about development, land use, and conservation.

Ian M. Shiach
Graduate Student

Ian Shiach is a M.S. candidate in the School of Natural Resources and the Environment at the University of Arizona. His interests include the impacts of drought and high temperature on plant physiology in arid climates, the socioeconomic consequences of drought, and the communication of environmental science concepts to non-specialists. He hopes to help facilitate open communication between drought scientists and stakeholders in vulnerable areas, so that so that communities can best prepare for and mitigate the effects of ongoing and future megadroughts.