Western North American megadrought

Western North American megadrought
Name	Western North American megadrought
Duration	21st century–present
Location	Western North America
Type	Drought
Causes	Anthropogenic warming; Pacific variability

Contents

Western North American megadrought is a prolonged severe drought event affecting the western regions of the North American continent that has intensified in the late 20th and early 21st centuries. The event has been analyzed by researchers across institutions such as National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration, United States Geological Survey, University of Arizona, and University of California, Los Angeles, and debated in forums including the Intergovernmental Panel on Climate Change and the United Nations Framework Convention on Climate Change. It intersects with policy discussions involving the Bureau of Reclamation, California Department of Water Resources, and transboundary agreements like the Colorado River Compact.

Definition and temporal scope

Scholars at Lamont–Doherty Earth Observatory, Scripps Institution of Oceanography, and Purdue University characterize the phenomenon as a multi-decadal precipitation and soil moisture deficit across regions including California, Nevada, Arizona, New Mexico, Utah, Colorado, and parts of Mexico. Paleoclimatologists at University of Arizona and University of Washington compare the recent interval with historical megadrought intervals reconstructed by teams at University of Minnesota and Pennsylvania State University, situating it within the context of megadrought definitions used by the American Geophysical Union and literature produced by the Geological Society of America. Temporal bounds frequently cited span late 20th century onset with marked intensification during the 2000s and 2010s in analyses by Harvard University and Columbia University.

Attribution studies from National Center for Atmospheric Research, Met Office Hadley Centre, and Lawrence Berkeley National Laboratory emphasize the role of anthropogenic greenhouse gas forcing traced by Intergovernmental Panel on Climate Change assessments and emissions inventories from entities like the Environmental Protection Agency. Modeled contributions from Pacific sea surface temperature patterns, including El Niño–Southern Oscillation, Pacific Decadal Oscillation, and central Pacific warming documented by NOAA researchers, interact with warming-driven evaporative demand described in research from University of California, Irvine and Oregon State University. Atmospheric circulation shifts linked to the Arctic Oscillation and stratospheric influences examined at National Center for Atmospheric Research and NASA Jet Propulsion Laboratory further modulate precipitation. Studies published with coauthors from Princeton University and Massachusetts Institute of Technology highlight combined thermodynamic and dynamic mechanisms.

Hydrological analyses by United States Geological Survey and water managers at Metropolitan Water District of Southern California document reductions in Lake Mead and Lake Powell storage, altered inflows to Sacramento–San Joaquin River Delta, and diminished snowpack across the Sierra Nevada (United States), Cascade Range, and Rocky Mountains. Impacts on municipal systems in Los Angeles, Phoenix, and Las Vegas intersect with agriculture basins such as the Central Valley and Imperial Valley, and with transboundary water sharing under the International Boundary and Water Commission. Forest health declines have been recorded in Sierra National Forest, San Bernardino National Forest, and Gila National Forest with monitoring by the United States Forest Service.

Economic assessments from Brookings Institution, Resources for the Future, and researchers at University of California, Berkeley estimate substantial impacts on irrigated agriculture in counties like Fresno County and Maricopa County, energy generation at facilities operated by Pacific Gas and Electric Company and Salt River Project, and municipal budgets for cities including San Diego and Denver. Public health implications have been documented by teams affiliated with Centers for Disease Control and Prevention and Johns Hopkins Bloomberg School of Public Health, particularly relating to wildfire smoke from ignitions in regions overseen by the National Interagency Fire Center and biodiversity losses affecting species monitored by the U.S. Fish and Wildlife Service and conservation organizations like The Nature Conservancy.

Dendrochronologists at University of Arizona and Tree-Ring Society use tree-ring chronologies from species such as Ponderosa pine, Bristlecone pine, and Douglas fir to reconstruct past hydroclimate; these records are complemented by lake sediment studies from teams at University of Minnesota and speleothem analyses carried out at University of Nevada, Reno. Multiproxy syntheses led by researchers at Columbia University and University of California, Santa Barbara integrate ice-core comparisons from Greenland ice sheet projects and coral records analyzed at Woods Hole Oceanographic Institution. Statistical methods employed include paleoclimate network approaches developed at NOAA Paleoclimatology and data assimilation techniques advanced at Lawrence Livermore National Laboratory.

Recent trend analyses published by Nature Climate Change groups with contributors from Princeton University and University of Colorado Boulder show increased aridity and soil moisture deficits consistent with projections from Coupled Model Intercomparison Project ensembles used in Intergovernmental Panel on Climate Change reports. Regional projections produced by teams at Scripps Institution of Oceanography and University of California, Davis indicate heightened risk of recurrence and intensification under Representative Concentration Pathways employed by Intergovernmental Panel on Climate Change assessments. Water resource scenario modeling involving Bureau of Reclamation and academic partners suggests persistent stress on reservoirs like Shasta Lake and cross-border flows affecting Rio Grande management frameworks.

Adaptation measures pursued by state agencies such as the California Department of Water Resources and Arizona Department of Water Resources include investments in desalination studies involving United States Department of the Interior funding, managed aquifer recharge projects coordinated with Central Arizona Project, and demand-management programs implemented by municipal utilities in San Francisco and Portland. Policy debates feature stakeholders including the Western Governors' Association, tribal authorities like the Yurok Tribe and Pueblo of Zuni, agricultural interest groups such as the California Farm Bureau Federation, and environmental litigants represented through organizations like Sierra Club and Earthjustice. Internationally, lessons inform dialogues at United Nations Convention to Combat Desertification meetings and influence transboundary water diplomacy practices in basins managed under instruments like the Colorado River Compact.

Category:Climate events