Greg Pederson, Ph.D.
Greg Pederson is a research scientist working primarily on the role of climate variability in driving changes in water resources, and other biological and physical components of mountainous ecosystems in western North America.
Research Interests
Of particular interest is the magnitude of low-frequency hydroclimatic variability and its implications for drought risk, as well as the climatic drivers associated with observed changes in mountain snowpack, streamflow, glaciers, and forest disturbance events. Understanding the time intervals and spatial scales over which these processes operate requires a long-term perspective, and for that I rely on proxy records primarily from tree-ring and lake sediments along with instrumental and modeled climate records. Recent and ongoing studies have addressed the susceptibility of natural resources to climate variability and change, and sought to apply both the modern and paleoclimatic records to present day resource management problems.
Current Research Projects Include:
- Drivers of Drought in the Upper Colorado River Basin [DOI Southwestern CSC]
- Multi-century perspectives on current and future streamflow in the Missouri River Basin [NSF P2C2]
- Reconstructions of Columbia River flow from winter and summer precipitation sensitive proxies in the Northwestern U.S. with implications for 21st century flow [CSC and CLU]
- A Broader view of North American climate over the past two millennia: Synthesizing paleoclimate records from diverse archives [USGS Powell Center]
- Holocene climate variability in Alaska from relict wood [DOI Alaska CSC]
- Holocene climates of the Northern Rockies from relict wood emerging from ice patches [CLU]
- Megadroughts and uncertainty in Upper Colorado River flow low-frequency variability [CLU]
Education and Certifications
Ph.D. Watershed Management & Ecohydrology. 2010. University of Arizona, School of Natural Resources.
M.S. Environmental Science. 2004. Montana State University
B.S. Ecology and Evolution in Botany & Zoology. 2000. Michigan State University
Affiliations and Memberships*
Greg is affiliate faculty with the Earth Sciences department and the Institute on Ecosystems (IoE) at Montana State University.
Science and Products
Reassessment of the Upper Fremont Glacier ice-core chronologies by synchronizing of ice-core-water isotopes to a nearby tree-ring chronology
Reconstructions of Columbia River streamflow from tree-ring chronologies in the Pacific Northwest, USA
Increasing influence of air temperature on upper Colorado River streamflow
Coherent late-Holocene climate-driven shifts in the structure of three Rocky Mountain lakes
The shifting climate portfolio of the Greater Yellowstone Area
Climate-induced changes in lake ecosystem structure inferred from coupled neo- and paleoecological approaches
Assessing the risk persistent drought using climate model simulations and paleoclimate data
Variability common to first leaf dates and snowpack in the western conterminous United States
The continuum of hydroclimate variability in western North America during the last millennium
Regional patterns and proximal causes of the recent snowpack decline in the Rocky Mountains, U.S.
Leveraging modern climatology to increase adaptive capacity across protected area networks
Northern Hemisphere modes of variability and the timing of spring in western North America
Science and Products
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Filter Total Items: 58
Reassessment of the Upper Fremont Glacier ice-core chronologies by synchronizing of ice-core-water isotopes to a nearby tree-ring chronology
The Upper Fremont Glacier (UFG), Wyoming, is one of the few continental glaciers in the contiguous United States known to preserve environmental and climate records spanning recent centuries. A pair of ice cores taken from UFG have been studied extensively to document changes in climate and industrial pollution (most notably, mid-19th century increases in mercury pollution). Fundamental to these sAuthorsNathan J. Chellman, Joseph R. McConnell, Monica Arienzo, Gregory T. Pederson, Sarah Aarons, Adam CsankReconstructions of Columbia River streamflow from tree-ring chronologies in the Pacific Northwest, USA
We developed Columbia River streamflow reconstructions using a network of existing, new, and updated tree-ring records sensitive to the main climatic factors governing discharge. Reconstruction quality is enhanced by incorporating tree-ring chronologies where high snowpack limits growth, which better represent the contribution of cool-season precipitation to flow than chronologies from trees positAuthorsJeremy S. Littell, Gregory T. Pederson, Stephen T. Gray, Michael Tjoelker, Alan F. Hamlet, Connie A. WoodhouseIncreasing influence of air temperature on upper Colorado River streamflow
This empirical study examines the influence of precipitation, temperature, and antecedent soil moisture on upper Colorado River basin (UCRB) water year streamflow over the past century. While cool season precipitation explains most of the variability in annual flows, temperature appears to be highly influential under certain conditions, with the role of antecedent fall soil moisture less clear. InAuthorsConnie A. Woodhouse, Gregory T. Pederson, Kiyomi Morino, Stephanie A. McAfee, Gregory J. McCabeCoherent late-Holocene climate-driven shifts in the structure of three Rocky Mountain lakes
Large-scale atmospheric pressure centers, such as the Aleutian and Icelandic Low, have a demonstrated relationship with physical lake characteristics in contemporary monitoring studies, but the responses to these phenomena are rarely observed in lake records. We observe coherent changes in the stratification patterns of three deep (>30 m) lakes inferred from fossil diatom assemblages as a responseAuthorsJeffery R. Stone, Jasmine E. Saros, Gregory T. PedersonThe shifting climate portfolio of the Greater Yellowstone Area
Knowledge of climatic variability at small spatial extents (< 50 km) is needed to assess vulnerabilities of biological reserves to climate change. We used empirical and modeled weather station data to test if climate change has increased the synchrony of surface air temperatures among 50 sites within the Greater Yellowstone Area (GYA) of the interior western United States. This important biologicaAuthorsAdam J. Sepulveda, Mike T Tercek, Robert K. Al-Chokhachy, Andrew Ray, David P. Thoma, Blake R. Hossack, Gregory T. Pederson, Ann Rodman, Tom OlliffClimate-induced changes in lake ecosystem structure inferred from coupled neo- and paleoecological approaches
Over the 20th century, surface water temperatures have increased in many lake ecosystems around the world, but long-term trends in the vertical thermal structure of lakes remain unclear, despite the strong control that thermal stratification exerts on the biological response of lakes to climate change. Here we used both neo- and paleoecological approaches to develop a fossil-based inference modelAuthorsJasmine E. Saros, Jeffery R. Stone, Gregory T. Pederson, Krista Slemmons, Trisha Spanbauer, Anna Schliep, Douglas Cahl, Craig E. Williamson, Daniel R. EngstromAssessing the risk persistent drought using climate model simulations and paleoclimate data
Projected changes in global rainfall patterns will likely alter water supplies and ecosystems in semiarid regions during the coming century. Instrumental and paleoclimate data indicate that natural hydroclimate fluctuations tend to be more energetic at low (multidecadal to multicentury) than at high (interannual) frequencies. State-of-the-art global climate models do not capture this characteristiAuthorsToby R. Ault, Julia E. Cole, Jonathan T. Overpeck, Gregory T. Pederson, David M. MekoVariability common to first leaf dates and snowpack in the western conterminous United States
Singular value decomposition is used to identify the common variability in first leaf dates (FLDs) and 1 April snow water equivalent (SWE) for the western United States during the period 1900–2012. Results indicate two modes of joint variability that explain 57% of the variability in FLD and 69% of the variability in SWE. The first mode of joint variability is related to widespread late winter–sprAuthorsGregory J. McCabe, Julio L. Betancourt, Gregory T. Pederson, Mark D. SchwartzThe continuum of hydroclimate variability in western North America during the last millennium
The distribution of climatic variance across the frequency spectrum has substantial importance for anticipating how climate will evolve in the future. Here we estimate power spectra and power laws (ß) from instrumental, proxy, and climate model data to characterize the hydroclimate continuum in western North America (WNA). We test the significance of our estimates of spectral densities and ß againAuthorsToby R. Ault, Julia E. Cole, Jonathan T. Overpeck, Gregory T. Pederson, Scott St. George, Bette Otto-Bliesner, Connie A. Woodhouse, Clara DeserRegional patterns and proximal causes of the recent snowpack decline in the Rocky Mountains, U.S.
We used a first-order, monthly snow model and observations to disentangle seasonal influences on 20th century,regional snowpack anomalies in the Rocky Mountains of western North America, where interannual variations in cool-season (November–March) temperatures are broadly synchronous, but precipitation is typically antiphased north to south and uncorrelated with temperature. Over the previous eighAuthorsGregory T. Pederson, Julio L. Betancourt, Gregory J. McCabeLeveraging modern climatology to increase adaptive capacity across protected area networks
Human-driven changes in the global environment pose an increasingly urgent challenge for the management of ecosystems that is made all the more difficult by the uncertain future of both environmental conditions and ecological responses. Land managers need strategies to increase regional adaptive capacity, but relevant and rapid assessment approaches are lacking. To address this need, we developedAuthorsJ.E. Davison, L.J. Graumlich, E.L. Rowland, Gregory T. Pederson, D.D. BreshearsNorthern Hemisphere modes of variability and the timing of spring in western North America
Spatial and temporal patterns of variability in spring onset are identified across western North America using a spring index (SI) model based on weather station minimum and maximum temperatures (Tmin and Tmax, respectively). Principal component analysis shows that two significant and independent patterns explain roughly half of the total variance in the timing of spring onset from 1920 to 2005. HAuthorsT.R. Ault, A.K. Macalady, G.T. Pederson, J.L. Betancourt, M.D. Schwartz - News
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