Scott St. George

Scott St. George
University of Minnesota Twin Cities | UMN · Department of Geography, Environment and Society

PhD

About

85
Publications
37,374
Reads
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2,297
Citations
Introduction
I‘m an earth scientist, and most of my research deals with topics in paleoclimatology, climate dynamics, natural hazards and climate impacts on renewable energy. My specialities are dendrochronology and dendroclimatology, low-frequency behavior in the climate system, and the northern Great Plains during the late Holocene.
Additional affiliations
August 2010 - November 2015
University of Minnesota Twin Cities
Position
  • Professor (Assistant)
March 2009 - August 2010
Natural Resources Canada
Position
  • Researcher
March 2009 - August 2010
Natural Resources Canada
Position
  • Researcher
Education
September 2003 - October 2007
The University of Arizona
Field of study
  • Geosciences

Publications

Publications (85)
Article
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Tropical and subtropical forests cover only 7 % of the Earth's land surface. Yet, they host nearly half of global tree density with a high species number (~40,000 species), store up to 25 % of global terrestrial carbon and represent one-third of net primary productivity on Earth. Over the last four decades, the study of tree growth in the tropics h...
Article
Over the past century, the Red River of the North has been the least stationary river in the continental United States. In Canada, historical and paleoenvironmental evidence indicates severe floods were common during the early 1800s, with the record ce 1826 flood having an estimated peak discharge 50% higher than the second-most severe flood ever o...
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Tree-ring chronologies underpin the majority of annually-resolved reconstructions of Common Era climate. However, they are derived using different datasets and techniques, the ramifications of which have hitherto been little explored. Here, we report the results of a double-blind experiment that yielded 15 Northern Hemisphere summer temperature rec...
Article
Tree growth rings contain yearly information about climate, extreme weather events, and other growing conditions. In this analysis, we model the relationship strength between tree-ring records with respect to location and time. We employ the discrete wavelet transformation on the ring width records in order to de-correlate the observations within e...
Presentation
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Tree rings and other natural archives empower us to extend our perspective on environmental change, resources, and hazards. But many contemporary applications of paleoclimatology and paleohydrology are useful because of the lasting disruption to our collective environmental memory caused by colonization.
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Plain Language Summary The subtropical jet stream (STJ) is a band of high‐speed westerly winds in the upper atmosphere located near the subtropics. Since the 1980s, the STJ has generally moved poleward, but its behavior varies strongly by region and season. We studied the STJ over the Himalayas and found, during 1948–2018, that the spring STJ is ty...
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Geological and botanical archives can preserve evidence of exceptional floods going back centuries to millennia. Updated risk guidelines offer a new opportunity to apply lessons from paleoflood hydrology to judge the odds of future floods.
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Across the Upper Missouri River Basin, the recent drought of 2000 to 2010, known as the “turn-of-the-century drought,” was likely more severe than any in the instrumental record including the Dust Bowl drought. However, until now, adequate proxy records needed to better understand this event with regard to long-term variability have been lacking. H...
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The new PAGES2k global compilation of temperature-sensitive proxies offers an unprecedented opportunity to study regional to global trends associated with orbitally driven changes in solar irradiance over the past 2 millennia. Here, we analyze pre-industrial long-term trends from 1 to 1800 CE across the PAGES2k dataset and find that, in contrast to...
Article
Tree rings serve regularly as the foundation for retrospective assessments of climate change and forest ecology. Thousands of tree-ring chronologies worldwide are available without restriction, but the interpretation of these preprocessed records are complicated by fundamental aspects of their construction.
Article
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A few modest adjustments to the planning and delivery of talks can help scientists share ideas with their peers more effectively.
Article
Previous work demonstrated the global variability of synchrony in tree growth within populations, that is, the covariance of the year‐to‐year variability in growth of individual neighbouring trees. However, there is a lack of knowledge about the causes of this variability and its trajectories through time. Here, we examine whether climate can expla...
Article
Ecological processes, such as migration and phenology, are strongly influenced by climate variability. Studying these processes often relies on associating observations of animals and plants with climate indices, such as the El Niño–Southern Oscillation (ENSO). A common characteristic of climate indices is the simultaneous emergence of opposite ext...
Article
Paleohydrologic records can provide unique, long-term perspectives on streamflow variability and hydroclimate for use in water resource planning. Such long-term records can also play a key role in placing both present day events and projected future conditions into a broader context than that offered by instrumental observations. However, relative...
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Were extended warm or cold periods in the past worldwide, or only regional? Efforts to reconstruct Earth’s climate history suggest that the near-global extent of ongoing warming is unparalleled over the past 2,000 years.
Article
War has an immediate and obvious effect on people and communities, but its impacts on local ecology can be more subtle. This paper shows how one military encounter in the Second World War has left a clear legacy in the northern forests of Norway, trackable more than seventy years later. We used annual growth rings of ~180 pine and ~30 birch trees a...
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The 692 proxy records of the new PAGES 2k compilation offer an unprecedented opportunity to study regional to global temperature trends associated with orbitally-driven changes in solar irradiance over the past two millennia. Here, we analyse the significance of long-term trends from 1–1800 CE in the PAGES 2k compilation’s tree-ring, ice core, mari...
Article
Pine forests provide goods and services crucial to more than ten million people living in the middle-mountains (600-4000 m) of Nepal. These critically important forests are already often overexploited and could be at risk from future climate change. In order to investigate the combined effects of climate and human disturbances on the growth of pine...
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We review the current generation of large-scale, millennial-length temperature reconstructions derived from tree rings and highlight areas of agreement and disagreement among these state-of-the-art paleotemperature estimates. Although thousands of tree ring-width chronologies are now available from temperate and boreal forest sites across the North...
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The standard approach to flood frequency analysis (FFA) fits mathematical functions to sequences of historic flood data and extrapolates the tails of the distribution to estimate the magnitude and likelihood of extreme floods. Here we identify the most exceptional floods in the United States as compared against other major floods at the same locati...
Article
Proxy evidence is necessary to place current temperature and hydroclimatic changes in a long–term context and to assess the full range of natural and anthropogenic climate forcings. Here, we present the first millennium–length reconstruction of late summer (August–September) temperature variability for the Mediterranean region. We compiled 132 maxi...
Presentation
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Even after more than a century of coordinated monitoring, instrumental weather observations are still too short to adequately constrain decadal or multidecadal behavior in the Earth’s climate system. Leading climatologists and climate modelers have called for the wider application of high-resolution proxy records to decadal variability and predicti...
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River flooding is among the most destructive of natural hazards globally, causing widespread loss of life, damage to infrastructure and economic deprivation. Societies are currently under increasing threat from such floods, predominantly from increasing exposure of people and assets in flood‐prone areas, but also as a result of changes in flood mag...
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While reflecting on his 12-year term as governor of Colorado, Richard Lamm recalled that his "most terrifying" day in office was the one he spent at Colorado State University learning about tree rings.1 Around that time, the late 1970s, the states water needs were becoming more and more difficult to manage under the auspices of the Colorado River C...
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Key message Pinus sylvestris tree-ring δ¹³C and δ¹⁸O records from locally moist sites in central and northern Sweden contain consistently stronger climate signals than their dry site counterparts. Abstract We produced twentieth century stable isotope data from Pinus sylvestris trees near lakeshores and inland sites in northern Sweden (near Kiruna)...
Article
Over the past two decades, the dendroclimate community has produced various annually resolved, warm season temperature reconstructions for the extratropical Northern Hemisphere. Here we compare these tree-ring based reconstructions back to 831 CE and present a set of basic metrics to provide guidance for non-specialists on their interpretation and...
Presentation
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So much of what we know about the Earth’s climate during the past two millennia comes from tree rings. Information gleaned from the physical or chemical properties of growth rings in trees have allowed us to extend hemispheric-scale temperature records back by several centuries, construct annual maps of drought severity that span several continents...
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The Mississippi River is shackled by one of the world’s largest systems of flood control. A palaeohydrological record suggests that those measures might actually be making floods worse.
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The western United States was affected by several megadroughts during the last 1200 years, most prominently during the Medieval Climate Anomaly (MCA: 800 to 1300 CE). A null hypothesis is developed to test the possibility that, given a sufficiently long period of time, these events are inevitable and occur purely as a consequence of internal climat...
Presentation
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In this talk, I argued the fossil tree-ring record from Chemnitz does not constitute reliable evidence of solar activity during the Permian because the individual tree-ring sequences are not correctly aligned and, as a result, the mean ring-width composite is not a meaningful estimate of year-to-year variations in tree growth in this ancient forest...
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In their study of tree rings from the Chemnitz Fossil Forest (Germany), Luthardt and Rößler (2017) claim to identify a regular near-11-yr cyclicity in growth, and present that pattern as evidence of the influence of the Schwabe solar cycle on climate and forest productivity during the early Permian. If correctly interpreted, these fossil tree rings...
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Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all conti...
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The study of Decadal Climate Variability and Predictability (DCVP) is the interdisciplinary scientific enterprise to characterize, understand, attribute, simulate, and predict the slow, multi-year variations of climate on global and regional scales.
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The climate of Nepal has changed rapidly over the recent decades, but most instrumental records of weather and hydrology only extend back to the 1980s. Tree rings can provide a longer perspective on recent environmental changes, and since the early 2000s, a new round of field initiatives by international researchers and Nepali scientists have more...
Presentation
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Prolonged episodes of persistently dry or wet conditions are common features of most proxy-based reconstructions of past hydroclimatic variability. These so-called “Joseph” events might be due to external forcings that push sea-surface temperatures into warm or cold states, and thereby increase the likelihood of widespread megadroughts or megapluvi...
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Music is inherently narrative and is known to exert a powerful influence on human emotions. Here we report on a collaboration between scientists and artists at the University of Minnesota that uses music to report the evidence of climate change in an engaging and visceral way.
Article
Elevation is a strong determinant of local climate and may therefore be an important factor to consider when examining the association between climate and tree growth. In this study, we developed a set of tree-ring width records for Abies spectablis (D.Don Spach) in the Manang Valley of central Nepal Himalaya and tested how tree growth and the rela...
Article
Palaeohydrology is now recognized as a valuable approach to characterize the hazards posed by flooding. Tree rings have emerged as an important source of evidence for paleohydrological studies, and, since the 1960s, have been used to document the occurrence of past floods. In this progress report we outline the major contributions of tree-ring reco...
Chapter
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The Red River, Manitoba, Canada, is a low-gradient, meandering river that traverses the broad, flat Red River Valley on the northeastern portion of the Great Plains of North America. The shallow stream-cut valley occupied by the river has insufficient capacity to contain large discharges, which allows higher magnitude flows to overtop the valley si...
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As the largest body of water on the northern Great Plains of North America, Lake Winnipeg in central Manitoba, Canada, is crucial to the region’s hydrology, economy, and society. Previous research identified exposed subfossil stumps at several locations along the shore in both the lake’s north and south basins, and interpreted them as evidence of l...
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This review describes the structure and characteristics of the Northern Hemisphere tree-ring width network, and examines the associations between these data and key aspects of local climate and the global climate system. Even though all ring-width records describe the same aspect of tree growth, there are major regional differences in the nature an...
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The width of an annual tree ring is without question a very simple indicator of the character of that year’s weather, but collectively, the global network of tree-ring width measurements represents an invaluable resource for high-resolution paleoclimatology.
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The distribution of climatic variance across the frequency spectrum has substantial importance for anticipating how climate will evolve in the future. Here power spectra and power laws (beta) are estimated from instrumental, proxy, and climate model data to characterize the hydroclimate continuum in western North America (WNA). The significance of...
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We present a synthesis of locally absent (or “missing”) growth rings across the Northern Hemisphere based on 2359 publicly available tree ring-width records. During the last millennium, widespread absent rings have been observed only in the southwestern United States and were associated with severe drought. Absent rings were uncommon during the gro...
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[1] Estimates of future flood risks are based on the observations of past floods, but instrumental records of basin hydrology are often too short to assess potential changes in the frequency or magnitude of extreme floods over time. In this study, we show that bur oak (Quercus macrocarpa Michx.) growing along the Red River of the North in North Dak...
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We assess the magnitude of decadal to multidecadal (D2M) variability in Climate Model Intercomparison Project 5 (CMIP5) simulations that will be used to understand, and plan for, climate change as part of the Intergovernmental Panel on Climate Change's 5th Assessment Report. Model performance on D2M timescales is evaluated using metrics designed to...
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We examined a set of five proxy reconstructions of the Pacific Decadal Oscillation (PDO) to test whether the choice of reconstruction affected the association between the PDO and widespread forest fires in the western United States. Exact binomial tests suggest the PDO has little direct impact on wildfires, with a statistically-significant associat...
Article
Craters of the Moon (COM) National Monument is a basaltic volcanic complex on the eastern Snake River Plain that has formed over eight eruptive periods during the Holocene. Since the last eruption, limber pine (Pinus flexilis) and Douglas-fir (Pseudotsuga menziesii Mirb Franco.) have established on lava flows and ancient weathered cinder cones. The...
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The central Pacific Coast of the United States is one of the few regions in North America where precipitation exhibited a high proportion of variance at decadal time scales (10 to 20 years) during the last century. We use a network of tree ring-width records to estimate the behavior of the observed decadal pattern in regional winter precipitation d...
Article
Most dendroclimatic studies assess past changes in decadal variability by first reconstructing an annually-resolved target variable, and then applying some form of filter that emphasizes variability within a specific frequency band. We evaluate the ability of a network of tree-ring records along the central Pacific Coast of the United States (herea...
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We examine how the seasonality of precipitation signals embedded within the North American Drought Atlas varies across the continent. Instrumental records of average summer (JJA) Palmer Drought Severity Index (PDSI) are characterized by major regional differences in the relative importance of precipitation during summer and winter (DJF). The Atlas,...
Chapter
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Each year, floods cause enormous damage to property and kill thousands of people around the world. During the 1990s alone, freshwater flooding affected more than 1.4 billion people and caused about 100,000 deaths (Jonkman 2005). Worldwide, insured losses due to floods topped US$2 billion in 2008 (SwissRe 2009), making them the second-most expensive...
Chapter
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Spring flooding along the Red River is one of Canada’s most disruptive natural hazards. In 1997, floodwaters from the Red inundated more than 2,000 km2 in Canada and the United States and threatened communities through-out the Red River basin (Fig. 1). Dubbed the ‘flood of the century’ by local media, the 1997 flood caused more than CDN $500 millio...
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Recent studies have suggested that the risk of drought over North America changes at timescales of one to several decades, and that these changes are coherent over large areas. We present a complementary perspective that measures the importance of these signals at the local scale. We use singular spectrum analysis to identify regions in North Ameri...
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Analysis of long-term terrestrial wind speed (u) records demonstrates that interannual variability is a major component of near-surface wind dynamics in the southern Canadian Prairies (SCP). Since the early 1950s, there have been several periods when negative anomalies in regional u persisted for 8 to 13 consecutive months, with anomalies for indiv...
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Ring-width data from 138 sites in the Canadian Prairie Provinces and adjacent regions are used to estimate summer drought severity during the past several hundred years. The network was divided into five regional groups based on geography, tree species, and length of record: the eastern Rockies, northern Saskatchewan, central Manitoba, southern Man...
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A network of 54 ring-width chronologies is used to estimate changes in summer climate within the Winnipeg River basin, Canada, since AD 1783. The basin drains parts of northwestern Ontario, northern Minnesota and southeastern Manitoba, and is a key area for hydroelectric power production. Most chronologies were developed from Pinus resinosa and P....
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This study uses a network of long-term discharge gauges to examine how river flow in the Winnipeg River basin, Canada has behaved during the last one hundred years. The Winnipeg River influences the production of over 4600 MW of hydroelectricity, and is the most important component of the hydrological system used to generate power in Manitoba. Extr...
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Winnipeg, Manitoba, Canada, has a large, indigenous population of bur oak (Quercus macrocarpa Michx.). In the 1980s, many of these trees were showing signs of decline, a disease caused by a complex of abiotic and secondary biotic stressing agents. Potential causal factors were investigated by comparing various aspects of 120 bur oaks visually rated...
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Paleohydrology uses indirect evidence to describe the behaviour of hydrological or hydroclimatic systems prior to the initiation of direct monitoring. This evidence can be derived from either human sources or natural archives. The articles in this issue show how paleoenvironmental data may be used to: i) place recent observations within a context o...
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Dendrochemical analysis was conducted on Quercus macrocarpa Michx. (bur oak) growing within the floodplain of the Red River, Canada, to determine if xylem formed during severe floods contained significantly perturbed chemistry. Wood samples were taken from five living trees in the same stand and from three timbers from a 19 th -century building. La...
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Long term well hydrographs and estimated ground water levels derived from hydroclimatic and biological data were used to evaluate trends within the Upper Carbonate Aquifer (UCA) near Winnipeg, Canada, during the 20th Century. Ground water records from instruments have been kept since the early 1960s and are derived from piezometers in the overlying...