GEOG5839.15, signal processing

•

0 likes•1,540 views

Scott St. George

October 18
30 the ‘detrended’
ring-width
Signal processing I
The linear aggregate model of tree growth
index

DOWNLOAD THESE DATA

Cat Mesa (NM556) Fenton Lake (NM550)

Abouselman Spring (NM555) Rito de los Frijoles (NM501)

Baca (NM558) Los Alamos New Mexico (NM046)

h p://www.ldeo.columbia.edu/tree-ring-laboratory/resources/so ware

TREE-RING WIDTH DATA
pith

bark

THE PRINCIPLE OF AGGREGATE TREE GROWTH

Rt = At + Ct + δD1t + δD2t + Et

THE PRINCIPLE OF AGGREGATE TREE GROWTH

Rt = At + Ct + δD1t + δD2t + Et
size-related growth trend
caused by physiological aging

At
does not have a universal or predictable shape.

STANDARDIZATION

the ‘detrended’
ring-width
index

ARSTAN
autoregressive
standardization

PROGRAM ARSTAN

PRODUCES CHRONOLOGIES
FROM TREE-RING MEASUREMENT SERIES

BY DETRENDING AND INDEXING
(STANDARDIZING) THE SERIES,
THEN APPLYING

A ROBUST ESTIMATION
OF THE MEAN VALUE FUNCTION
TO REMOVE EFFECTS OF
ENDOGENOUS STAND DISTURBANCES.

DIVIDE
(A) the raw ring-width data
by (B) the ‘detrending’ curve

ARSTAN OUTPUT

CHRONOLOGY

EXERCISE
Use several diﬀerent detrending methods
to standardize our set of ring-width chronologies
and let’s see what happens!

STANDARDIZE THESE DATA

Cat Mesa (NM556) Fenton Lake (NM550)

Abouselman Spring (NM555) Rito de los Frijoles (NM501)

Baca (NM558) Los Alamos New Mexico (NM046)

USE FOUR DIFFERENT APPROACHES
TO STANDARDIZATION
Horizontal line
Negative exponential curve
20-yr ﬂexible spline
Flexible spline set to 67% of series length

GEOG5839
XT C L AS S
NE
WHO WILL FIND THE FIRST

“DIRTY DOG”?
Source: Terry Bain

More Related Content

Viewers also liked

Paleoclimate: past-climate as the key to understand the future. Example from ...

Paleoclimate: past-climate as the key to understand the future. Example from ...

Paleoclimate: past-climate as the key to understand the future. Example from ...

In many settings, trees growing on floodplains provide an important source of indirect evidence that may be used to infer the occurrence, extent, and magnitude of floods prior to direct observations. That evidence may take several forms, including external scars caused by abrasion or impact from floating debris, anatomical changes within the annual growth increment following prolonged stem or root inundation, or tilting or uprooting due to the hydraulic pressure of floodwaters. Likely the most useful characteristic of paleoflood studies based on floodplain trees is their relatively high temporal resolution and dating accuracy compared to most other methods. Dendrochronological methods can routinely date past floods to the year of their occurrence and, in rare cases, can estimate the timing of floods that occur during the growing season to within two weeks. This high degree of chronological control, which is surpassed only by that provided by direct observation or instrumentation, can be used to determine whether floods in separate watersheds were synchronous or offset by several years and test hypotheses that suppose linkages between extreme floods and specific forcing mechanisms. Furthermore, the wide geographic distribution of tree species with dateable rings combined with the broad suite of methods available to examine interconnections between floods and tree growth allow this style of paleoflood hydrology to be applied to many settings that are not suitable for techniques that depend on geological evidence. Future paleoflood research involving tree rings will need to strike a balance between improving our understanding of the biological and fluvial processes that link tree growth to past events, and providing answers to questions about flood dynamics and hazards that are needed to safeguard people and property from future floods.

Trees as flood sensors

Trees as flood sensors

Trees as flood sensors

Scott St. George

Implicit bias in higher ed - for undergraduates

Implicit bias in higher ed - for undergraduates

Implicit bias in higher ed - for undergraduates

In 1968, Benoit Mandelbrot and James Wallis published an article titled ‘Noah, Joseph, and operational Hydrology’ in the journal Water Resources Research. In it, they argued that hydrological models of the day were not able to estimate the true risk of extreme floods or prolonged drought, and that rare hydrological events were much more common than usually assumed. In this lecture, I’ll review how high-resolution paleoenvironmental archives can help us judge more accurately the risks posed by the ‘Noah’- and ‘Joseph’-style events described by Mandelbrot and Wallis. I’ll give particular emphasis to the environmental information recovered from the rings of ancient trees, and explain how dendrochronology (tree-ring research) has been used to redefine the ‘flood of record’, test potential avenues for long-lead climate predictions, and gage the performance of state-of-the-art climate models.

Noah, Joseph, And High-Resolution Paleoclimatology

Noah, Joseph, And High-Resolution Paleoclimatology

Noah, Joseph, And High-Resolution Paleoclimatology

Scott St. George

When climate science is communicated to the broader public, many of its key findings are shared in the form of conceptual diagrams or information-dense data graphics. In this collaboration, we applied a data sonification approach to express NASA’s global temperature record as a musical composition for the cello. The resulting piece, which we titled ‘A Song of Our Warming Planet’, transformed 133 years of annual global temperature anomalies into a haunting, atonal melody that stretched across almost all of the instrument’s range. Since its release in June 2013, the song has been featured by several national and international media outlets, including the New York Times, the Weather Channel, and National Public Radio, and its accompanying video has received more than 140,000 views from nearly every corner of the world. We are currently preparing a new composition for string quartet that will add a geographic dimension to describe both the pace and place of global warming. We believe the success of our initial sonification project is testament to the power of music to reach audiences who respond less enthusiastically to traditional methods used to communicate climate science. We also imagine this approach could be applied more broadly to allow students to create novel, visceral, and memorable encounters with other aspects of the geophysical sciences.

A Song of Our Warming Planet: Using Music to Communicate Critical Concepts in...

A Song of Our Warming Planet: Using Music to Communicate Critical Concepts in...

A Song of Our Warming Planet: Using Music to Communicate Critical Concepts in...

Scott St. George

The "Year Without A Summer" was not a year without a ring

The "Year Without A Summer" was not a year without a ring

The "Year Without A Summer" was not a year without a ring

Scott St. George

Large-scale low-frequency variability has emerged as a priority for climate research, but instrumental observations are not long enough to characterize this behavior or gage its impacts on dependent geophysical or ecological systems. As the leading source of high-resolution paleoclimate information in the middle- and high-latitudes, tree rings are essential to understand low-frequency variability prior to the instrumental period. But even though tree rings possess several advantages as climate proxies, like other natural archives they also have their own particular impediments. In this lecture, Dr. St. George will describe the structure and characteristics of the Northern Hemisphere tree-ring width network, and outline how the fingerprint of decadal and multidecadal climate variability encoded within ancient trees varies across the hemisphere.

Large-scale dendrochronology and low-frequency climate variability

Large-scale dendrochronology and low-frequency climate variability

Large-scale dendrochronology and low-frequency climate variability

Scott St. George

Measurements of tree-ring widths are the most widely-distributed and best replicated source of surrogate environmental information on the planet, and are one of the main archives used to estimate changes in regional and global climate during the past several centuries or millennia. Because the Northern Hemisphere ring-width network is now so large, it is more crucial than ever to ensure our understanding of tree-environment relations is not influenced by decisions to include or exclude certain records. It may be the case that a particular set of ring-width records are, for whatever reason, more tightly coupled to a particular climate factor than other records from the same region or species and, as a result, may be superior estimators of that factor’s past behavior. At the same time, it is known that selecting a small number of predictors from a large pool of potential candidates increases the likelihood of a Type I error. That effect may be particularly relevant to dendroclimatology because the total number of available ring-width records is often much larger than the number of records used to produce reconstructions of large-scale climate features. As an initial step, it would be helpful if paleoclimate reconstructions derived from tree rings described more explicitly the criteria used to select ring-width records as potential predictors and specified those records excluded by that screening. By comparing ring-width chronologies and their relations with climate against the standard set by thousands of records across the hemisphere, we should be better able to distinguish climate signals from proxy noise and produce more accurate reconstructions of climate during the late Holocene.

Guarding against false discovery in large-scale dendroclimatology

Guarding against false discovery in large-scale dendroclimatology

Guarding against false discovery in large-scale dendroclimatology

Scott St. George

These visuals were prepared to support a string quartet performance and panel on climate change at Northwestern University in February 2106. A well-designed graphic can help audiences to quickly understand the main message embedded within a complex set of climate data and to retain those ideas longer than they would have if they were conveyed by words alone. But the visual aids used regularly by climate scientists also have their limitations: they are most easily understood by people who are already fluent in technical illustrations; they're usually static and sometimes do not tell an obvious story; and for many, they don't elicit a strong emotional response. Music, by contrast, is inherently narrative and is known to exert a powerful influence on human emotions. Because of this, sonification — the transformation of data into acoustic signals — may have considerable promise as a tool to enhance the communication of climate science. Daniel Crawford and Scott St. George report on a collaboration between scientists and artists that uses music to transmit the evidence of climate change in an engaging and visceral way.

Making Climate Data Sing

Making Climate Data Sing

Making Climate Data Sing

Scott St. George

The ability to deliver effective and engaging oral presentations is a critical skill for all researchers. Unfortunately, despite the importance of clear communication, too many scientific presentations at conferences and workshops are confusing, abstract, and boring. In this short workshop, participants learn several key strategies and tips that will make their professional presentations just a little bit better than the rest. We discuss strategies for presentation planning, show how basic design principles can create more memorable slides, and point towards an outstanding set online tools and resources. Become a presentation superstar! Scott St. George is Associate Professor in the Department of Geography, Environment and Society at the University of Minnesota and a Resident Fellow at UMN's Institute on the Environment. Prior to joining the faculty at Minnesota, he was a research scientist with the Geological Survey of Canada. Scott shares some of his experiences ‘doing presentations differently’ at conferences, outreach opportunities, and the classroom.

Five Things You Can Do Right Now To Make Your Research Presentations Just A L...

Five Things You Can Do Right Now To Make Your Research Presentations Just A L...

Five Things You Can Do Right Now To Make Your Research Presentations Just A L...

Scott St. George

Strong variance at decadal and multidecadal timescales is a common feature of most tree-ring width records. But does this aspect of tree growth exhibit such long-memory behavior due to biology, climate, or some combination of the two factors? Understanding the origins of this behavior is crucial for efforts to evaluate the causes of decadal variability in the climate system. Presentation at Johann Gutenburg University (Mainz) on February 16, 2017.

Decadal variability in tree rings

Decadal variability in tree rings

Decadal variability in tree rings

Scott St. George

Viewers also liked (11)

Paleoclimate: past-climate as the key to understand the future. Example from ...

Paleoclimate: past-climate as the key to understand the future. Example from ...

Paleoclimate: past-climate as the key to understand the future. Example from ...

Trees as flood sensors

Trees as flood sensors

Trees as flood sensors

Implicit bias in higher ed - for undergraduates

Implicit bias in higher ed - for undergraduates

Implicit bias in higher ed - for undergraduates

Noah, Joseph, And High-Resolution Paleoclimatology

Noah, Joseph, And High-Resolution Paleoclimatology

Noah, Joseph, And High-Resolution Paleoclimatology

A Song of Our Warming Planet: Using Music to Communicate Critical Concepts in...

A Song of Our Warming Planet: Using Music to Communicate Critical Concepts in...

A Song of Our Warming Planet: Using Music to Communicate Critical Concepts in...

The "Year Without A Summer" was not a year without a ring

The "Year Without A Summer" was not a year without a ring

The "Year Without A Summer" was not a year without a ring

Large-scale dendrochronology and low-frequency climate variability

Large-scale dendrochronology and low-frequency climate variability

Large-scale dendrochronology and low-frequency climate variability

Guarding against false discovery in large-scale dendroclimatology

Guarding against false discovery in large-scale dendroclimatology

Guarding against false discovery in large-scale dendroclimatology

Making Climate Data Sing

Making Climate Data Sing

Making Climate Data Sing

Five Things You Can Do Right Now To Make Your Research Presentations Just A L...

Five Things You Can Do Right Now To Make Your Research Presentations Just A L...

Five Things You Can Do Right Now To Make Your Research Presentations Just A L...

Decadal variability in tree rings

Decadal variability in tree rings

Decadal variability in tree rings

Similar to GEOG5839.15, signal processing

Automated Generation of High-accuracy Interatomic Potentials Using Quantum Data

Automated Generation of High-accuracy Interatomic Potentials Using Quantum Data

Automated Generation of High-accuracy Interatomic Potentials Using Quantum Data

Pobuda_MDA

A Self-Organized Criticality Mutation Operator for Dynamic Optimization Problems

A Self-Organized Criticality Mutation Operator for Dynamic Optimization Problems

A Self-Organized Criticality Mutation Operator for Dynamic Optimization Problems

Carlos M. Fernandes

CAG Quebec 2008 - Prairie drought and tree rings

CAG Quebec 2008 - Prairie drought and tree rings

CAG Quebec 2008 - Prairie drought and tree rings

Scott St. George

GEOG5839.12, the linear aggreate model of tree growth

GEOG5839.12, the linear aggreate model of tree growth

GEOG5839.12, the linear aggreate model of tree growth

Scott St. George

MSSISS riBART 20160321

MSSISS riBART 20160321

MSSISS riBART 20160321

Yaoyuan Vincent Tan

This presentation delivered at the Toronto Geological Discussion Group (TGDG) explains the application of compositional data analysis, simplicial geometry, and predictive modeling of geochemical data to reconstruct skarn chemostratigraphy and calc-silicate alteration facies. I present a complete data driven approach in which advanced data analytics of geochemical data is at the core of geological understanding.

Geology, Chemostratigraphy, and Alteration Geochemistry of the Rosemont Cu-Mo...

Geology, Chemostratigraphy, and Alteration Geochemistry of the Rosemont Cu-Mo...

Geology, Chemostratigraphy, and Alteration Geochemistry of the Rosemont Cu-Mo...

Juan Carlos Ordóñez Calderón, Ph.D., P.Geo.

Anomaly Detection in Sequences of Short Text Using Iterative Language Models

Anomaly Detection in Sequences of Short Text Using Iterative Language Models

Anomaly Detection in Sequences of Short Text Using Iterative Language Models

Cynthia Freeman

Similar to GEOG5839.15, signal processing (8)

Automated Generation of High-accuracy Interatomic Potentials Using Quantum Data

Automated Generation of High-accuracy Interatomic Potentials Using Quantum Data

Automated Generation of High-accuracy Interatomic Potentials Using Quantum Data

Pobuda_MDA

A Self-Organized Criticality Mutation Operator for Dynamic Optimization Problems

A Self-Organized Criticality Mutation Operator for Dynamic Optimization Problems

A Self-Organized Criticality Mutation Operator for Dynamic Optimization Problems

CAG Quebec 2008 - Prairie drought and tree rings

CAG Quebec 2008 - Prairie drought and tree rings

CAG Quebec 2008 - Prairie drought and tree rings

GEOG5839.12, the linear aggreate model of tree growth

GEOG5839.12, the linear aggreate model of tree growth

GEOG5839.12, the linear aggreate model of tree growth

MSSISS riBART 20160321

MSSISS riBART 20160321

MSSISS riBART 20160321

Geology, Chemostratigraphy, and Alteration Geochemistry of the Rosemont Cu-Mo...

Geology, Chemostratigraphy, and Alteration Geochemistry of the Rosemont Cu-Mo...

Geology, Chemostratigraphy, and Alteration Geochemistry of the Rosemont Cu-Mo...

Anomaly Detection in Sequences of Short Text Using Iterative Language Models

Anomaly Detection in Sequences of Short Text Using Iterative Language Models

Anomaly Detection in Sequences of Short Text Using Iterative Language Models

More from Scott St. George

A good talk can open the doors to new collaborations, increase your chances of funding success, and make it more likely other people will respond to your ideas. But scientific presentations are too often confusing, boring, and overstuffed. Here are some suggestions, based on our experience as speakers, audience members, and presentation trainers, that we hope will make your next conference talk or seminar more enjoyable, engaging and effective.

Boosting the Signal: Simple Strategies to Deliver Better Scientific Talks

Boosting the Signal: Simple Strategies to Deliver Better Scientific Talks

Boosting the Signal: Simple Strategies to Deliver Better Scientific Talks

Scott St. George

Ringing true: The scientific and societal relevance of dendrochronology at th...

Ringing true: The scientific and societal relevance of dendrochronology at th...

Ringing true: The scientific and societal relevance of dendrochronology at th...

Scott St. George

Much of what we know regarding variations in Earth's climate during the past millennium comes from tree rings. But tree rings, like other proxies, attenuate some climate signals but amplify others, and their fidelity at longer timescales is difficult to gage. Even though dendroclimatology is well-established, questions remain about the climate clues encoded in tree rings — particularly at decadal-to-centennial timescales.

How long do trees remember?

How long do trees remember?

How long do trees remember?

Scott St. George

How long do we need to watch a river before its behavior holds no more surprises? In this country, instrumental measurements of river stage and discharge stretch back a century or more, but this observed history still provides only a rough guide to the risks of future extreme floods. In this lecture, I’ll outline how paleoflood hydrology expands our perspective on river history by combining historical, botanical, and geological evidence of earlier (and ofttimes unknown) floods. And I’ll explain how we can interpret those physical clues left behind by ancient floods to improve hazard assessments for at-risk communities, support decisions about flood infrastructure, and investigate the long-term effects of climate or land-use changes on flooding. Because what has happened before can happen again, most everyone near a river would profit by keeping a longer memory of old floods.

Don’t call it a comeback: Studying ancient floods to prepare for future hazards

Don’t call it a comeback: Studying ancient floods to prepare for future hazards

Don’t call it a comeback: Studying ancient floods to prepare for future hazards

Scott St. George

Flood rings: Paleoflood evidence in tree-ring anatomy

Flood rings: Paleoflood evidence in tree-ring anatomy

Flood rings: Paleoflood evidence in tree-ring anatomy

Scott St. George

Historic accounts of extreme floods on the Red River of the North

Historic accounts of extreme floods on the Red River of the North

Historic accounts of extreme floods on the Red River of the North

Scott St. George

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 prediction studies, and our community has responded by producing new paleoclimate products that specifically target this type of ‘intermediate-term’ behavior. But we now also know our medium changes that message: the biological and geological systems that encode climate information into natural archives often also alter the original ‘input’, usually due to either seasonal filtering or non-climatic persistence. In this talk, we’ll discuss some of the challenges inherent to the use of high-resolution proxies to study decadal or multi-decadal climate variability, and suggest strategies that might clarify how climate acts on those timescales. And we’ll also present a new theoretical framework that could help paleo-scientists evaluate competing ideas about the causes of decadal- or multi-decadal events known to have occurred during the past one or two millennia.

Disentangling the decadal ‘knot’ in high-resolution paleoclimatology

Disentangling the decadal ‘knot’ in high-resolution paleoclimatology

Disentangling the decadal ‘knot’ in high-resolution paleoclimatology

Scott St. George

We know from tree rings and other natural drought records that the western United States has been affected by several 'megadroughts' during the past millennium. But are these exceptionally long-lasting droughts due to unusual external forcings, or are they inevitable given a sufficiently long period of time? Here we present a statistical model that combines sea surface temperature records and drought severity statistics from the western USA, and use that tool to set out an expectation for megadrought, given no other changes in the climate system. Even though this model was trained using only modern climate data (and incorporates no information from tree rings or other proxies), it still produced megadroughts. Moreover, those simulated megadroughts were just as long-lasting, covered as large an area, and were just as severe as real megadroughts estimated from tree rings. That result means that megadroughts can occur in the western United States even if nothing else changes in the climate -- they really are just a matter of time. On the other hand, the only aspect of real-world megadroughts that the model cannot duplicate was the high number of these events during the so-called Medieval Climate Anomaly (800 to 1300 CE). So that cluster of megadroughts may have been caused by some sort of unusual climate circumstances that have not been observed by us during the past few decades. The proxy record tells us that many different kinds of exceptional or unusual climate events happened in the past. But it is often difficult to determine what caused those exceptional events because even, within a period of a thousand years, we still have very few cases. So besides being an aid to understand the causes of past megadroughts, we hope this approach can be applied to other paleoclimate records to distinguish between real interrelations between separate components of the climate system and simple coincidences.

A new framework to test the origins of western American megadrought

A new framework to test the origins of western American megadrought

A new framework to test the origins of western American megadrought

Scott St. George

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, and generate proxy estimates for many of the leading modes within the climate system. The theoretical foundation that underpins these products — and most others in dendroclimatology — was fully mature by the early 1990s and set out in detail by Cook and Kairiukstis in their seminal book, ‘Methods in Dendrochronology’. Most of the core analytical methods used to infer past climate from tree rings that appear in this reference (as well as prior works) depend on two concepts in particular: first, the idea that patterns common to many trees at many sites are more likely to be related to synoptic-scale climate variability (the principle of replication), and second, the notion that the most useful tree-ring records are found in forests where growth is particularly sensitive to a specific aspect of local climate (the principle of site selection). But because of (i) the gradual expansion, extension, and in-filling of the global tree-ring network and (ii) the emphasis given to atypical or even unique site-specific signals by some novel reconstruction methods, it is a point of debate within our community, at least implicitly, whether these principles remain valid. This presentation will review several recent studies that illustrate the possible advantages offered by a disregard for the usual ‘rules’ of dendroclimatology but will also discuss the potential pitfalls of placing too much emphasis on apparently optimal records. We hope this talk will encourage the sharing of ideas on how best to extract climate information from the ever-expanding network of tree-ring records across our planet and help open a discussion on the relevance of our standard theoretical framework to contemporary global dendroclimatology.

The need for new theory in global dendroclimatology

The need for new theory in global dendroclimatology

The need for new theory in global dendroclimatology

Scott St. George

Southern Manitoba is one of the most flood-prone regions in Canada, with the Red River of the North being the cause of most significant floods. The realization that the then-recent 1950 flood disaster was dwarfed by the historical 1826 flood led Canadian government officials to set an unusually high design standard for the Red River floodway, a 48-km long diversion built in the 1960s to protect the provincial capital of Winnipeg. And after paleoflood research confirmed new evidence of the 1826 flood, that event was cited as the main justification for expanding the Red River floodway, a $668 billion CAN infrastructure project that began in 2010. Without these insights from historical and paleoflood research, it’s almost certain flood risk estimates would have been unrealistically low and Winnipeg would have adopted a lesser level of flood protection. Because widespread Euro-American settlement in the Pembina Territory (the present-day Red River basin within the United States) did not occur until the 1870s, there are no historical accounts that indicate whether the 1826 flood was also so severe in North Dakota or Minnesota. As a result, the 1997 flood, which was nearly 1.5 times larger than any other previous flood in the US gage record, overwhelmed the dikes protecting Grand Forks and East Grand Forks. By having a deeper understanding of the history of flooding, communities are better able to anticipate future floods, make sound decisions about flood protection and migration, and protect people and their property more effectively.

The societal value of historical and paleoflood research in Manitoba, Canada

The societal value of historical and paleoflood research in Manitoba, Canada

The societal value of historical and paleoflood research in Manitoba, Canada

Scott St. George

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 (Usokin and Mursula, 2003) on climate and forest productivity during the early Permian. If correctly interpreted, these fossil tree rings would indicate the sunspot cycle was the dominant influence on interannual variability in Earth’s climate during this period and that it has been a consistent aspect of our Sun’s behavior for at least the past 300 m.y. We argue 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 (dendrochronologically dated) 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.

Solar ghosts: Weighing the evidence for sunspot cycles in fossil trees

Solar ghosts: Weighing the evidence for sunspot cycles in fossil trees

Solar ghosts: Weighing the evidence for sunspot cycles in fossil trees

Scott St. George

In the Biblical story of Joseph, following seven years of abundance, the Kingdom of Egypt was confronted by seven years of drought and famine. In the parlance of modern climate science, intervals with several consecutive extremely dry years are described as ‘“megadroughts”. In this short talk, I’ll describe how climate scientists combine clues from natural weather archives (including corals, tree rings, lake sediments, and many other sources) to reveal the history of ancient megadroughts across our planet. And I’ll highlight new research that combines these surrogate drought records with simulations from state-of-the-art climate models to help us better anticipate the risks of unusually persistent droughts during the coming century.

Long droughts: Using natural climate archives to gage the risks of future “me...

Long droughts: Using natural climate archives to gage the risks of future “me...

Long droughts: Using natural climate archives to gage the risks of future “me...

Scott St. George

As one of the most destructive hazards on our planet, floods kill thousands of people and cause billions of dollars in property damage every year. We usually try to gage the risk of future floods by fitting mathematic functions to hydrological data and then extrapolating the upper tail of those distributions. But because large floods are rare and river gage records are short, the conventional approach can sometimes drastically underestimate the threat posed to communities and infrastructure by extreme floods. In this lecture, I’ll argue that paleoflood hydrology — the study of ancient floods as recorded by river and lake sediments, trees, caves, and historical documents — is absolutely essential to judge the real risk of large, rare floods. And I’ll use examples from North America to illustrate how a ‘deeper river memory’ can help people evaluate their own vulnerability to floods, weigh the potential benefits of proposed infrastructure projects, and become more aware of what nature is truly capable of producing.

Expecting the unexpected: The relevance of old floods to modern hydrology

Expecting the unexpected: The relevance of old floods to modern hydrology

Expecting the unexpected: The relevance of old floods to modern hydrology

Scott St. George

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 megapluvials. Alternatively, internal ocean-atmosphere variability alone might be able to produce long-lasting and spatially extensive wet or dry intervals, even in the absence of any exotic external influences. In this study, we use a simple statistical emulator to establish benchmarks for decadal or multidecadal patterns in the western United States. We constructed a linear inverse model that included three key aspects of the El Niño-Southern Oscillation (monthly sea-surface temperatures, zonal surface wind stress, and sea-surface height), and restricted the spatial domain of each field to include only the tropical Pacific. By also including western United States hydroclimate information in the LIM, we are able to test whether ENSO variability and stochastic weather ‘noise’ could be sufficient to create low-frequency coherence within proxy networks. More broadly, if simulated drought patterns generated by the LIM are able to match the frequency, intensity, or spatial extent of droughts reconstructed by proxies, that implies that neither exotic forcings nor climate variability outside the tropical Pacific are required to produce widespread megadroughts in this region. If prolonged departures from the mean are indeed emergent but unremarkable features of western North America’s hydroclimate, we might be able to estimate their future occurrence as a linear combination of changes in the mean state and the linear dynamics that have governed their behavior in the past. S. St. George, T. Ault, C. Carrillo, S. Coats, J. Mankin, J. Smerdon, What to expect when you’re expecting decadal variability in hydroclimatic proxies, PAGES 5th Open Science Meeting, Zaragoza, Spain, May 9-13, 2017.

What to expect when you’re expecting decadal variability in hydroclimatic pro...

What to expect when you’re expecting decadal variability in hydroclimatic pro...

What to expect when you’re expecting decadal variability in hydroclimatic pro...

Scott St. George

Every year, trees in temperate and boreal forests go through a cycle of dormancy and activity that produces a new layer of tracheids, fibers and other woody cells around their stem. The end result of this process - a tree ring - is one of the most obvious signs in nature documenting the passage of time and the character of that year’s weather. Measurements of tree-ring widths are the most widely-distributed and best replicated source of surrogate environmental information on the planet and are one of the main archives used to estimate changes in regional and global climate during the past several centuries or millennia. In this lecture, I describe the structure and characteristics of the Northern Hemisphere tree-ring width network, and outline how these data are linked with key aspects of local climate and the global climate system. More generally, by describing the characteristics of the Northern Hemisphere tree-ring width network and the diversity of its relations with varying aspects of the global climate system, this presentation highlights the breadth and quality of environmental information that may be recovered from the width of annual growth layers in temperate and boreal trees.

Seeing the Forest for the Tree(Ring)s

Seeing the Forest for the Tree(Ring)s

Seeing the Forest for the Tree(Ring)s

Scott St. George

The decadal character of northern California's winter precipitation

The decadal character of northern California's winter precipitation

The decadal character of northern California's winter precipitation

Scott St. George

Anthropogenic climate change is one of the most challenging problems humanity faces, but public opinion surveys show that many people are skeptical about global warming. In this seminar, Dan Crawford, Scott St. George and Todd Reubold will share their experiences with using music to help climate science reach out to new audiences. Their first collaboration — a music video that reconfigures global temperature data as a cello composition — has been described as “amazing, and eerie” and “an effective tool to show people that our planet is changing.” Join us to learn what global warming sounds like!

Resonate! How 90 Seconds of Cello Music Is Helping People Connect With Climat...

Resonate! How 90 Seconds of Cello Music Is Helping People Connect With Climat...

Resonate! How 90 Seconds of Cello Music Is Helping People Connect With Climat...

Scott St. George

Background/Question/Methods Under environmental stress, boreal and temperate trees will occasionally form a discontinuous layer of wood about their stem, a condition described as a locally-absent (or “missing”) growth ring. Absent rings can potentially cause errors in tree-ring dates and dendroclimatic reconstructions but the frequency, distribution and controls of these features are not well understood at large spatial scales. Furthermore, the recent claim that the Northern Hemisphere tree-ring network contains multiple chronological errors caused by widespread but unrecognized locally-absent rings has been difficult to evaluate because it is not known where or when absent rings have occurred across boreal and temperate forests or what environmental factors cause the development of spatially-extensive absent rings. Here we present a synthesis of locally-absent rings across the Northern Hemisphere during the last millennium based on 2,359 publicly-available tree ring-width records. Results/Conclusions Over the entire dataset, one locally-absent ring was observed for every 240 visible rings. More than half of all records (1,296 of 2,359) did not contain a single absent ring. Absent rings were extremely uncommon at high latitudes; poleward of 50°N, the absent:visible ratio increased from 1:240 to 1:2,500. Absent rings were not widespread during the growing seasons that followed the four largest stratospheric sulfate aerosol injection events of the last millennium, including A.D. 1259 and the “Year Without a Summer” in A.D. 1816 or during the coldest year in the Northern Hemisphere in the last 1,500 years. Because these features have occurred so rarely in high-latitude and high-elevation tree ring-width records, the argument that paleotemperature estimates based on these data contain chronological errors due to unrecognized absent rings is not consistent with field observations. If however the rate of absent-ring formation were to increase in forests outside of the American Southwest, that behavior would represent a response to environmental stress that is without precedent over the last millennium.

Absent rings are rare in Northern Hemisphere forests outside the American Sou...

Absent rings are rare in Northern Hemisphere forests outside the American Sou...

Absent rings are rare in Northern Hemisphere forests outside the American Sou...

Scott St. George

GEOG5839.22, Paleofloods

GEOG5839.22, Paleofloods

GEOG5839.22, Paleofloods

Scott St. George

GEOG5839.21, The Colorado River

GEOG5839.21, The Colorado River

GEOG5839.21, The Colorado River

Scott St. George

More from Scott St. George (20)

Boosting the Signal: Simple Strategies to Deliver Better Scientific Talks

Boosting the Signal: Simple Strategies to Deliver Better Scientific Talks

Boosting the Signal: Simple Strategies to Deliver Better Scientific Talks

Ringing true: The scientific and societal relevance of dendrochronology at th...

Ringing true: The scientific and societal relevance of dendrochronology at th...

Ringing true: The scientific and societal relevance of dendrochronology at th...

How long do trees remember?

How long do trees remember?

How long do trees remember?

Don’t call it a comeback: Studying ancient floods to prepare for future hazards

Don’t call it a comeback: Studying ancient floods to prepare for future hazards

Don’t call it a comeback: Studying ancient floods to prepare for future hazards

Flood rings: Paleoflood evidence in tree-ring anatomy

Flood rings: Paleoflood evidence in tree-ring anatomy

Flood rings: Paleoflood evidence in tree-ring anatomy

Historic accounts of extreme floods on the Red River of the North

Historic accounts of extreme floods on the Red River of the North

Historic accounts of extreme floods on the Red River of the North

Disentangling the decadal ‘knot’ in high-resolution paleoclimatology

Disentangling the decadal ‘knot’ in high-resolution paleoclimatology

Disentangling the decadal ‘knot’ in high-resolution paleoclimatology

A new framework to test the origins of western American megadrought

A new framework to test the origins of western American megadrought

A new framework to test the origins of western American megadrought

The need for new theory in global dendroclimatology

The need for new theory in global dendroclimatology

The need for new theory in global dendroclimatology

The societal value of historical and paleoflood research in Manitoba, Canada

The societal value of historical and paleoflood research in Manitoba, Canada

The societal value of historical and paleoflood research in Manitoba, Canada

Solar ghosts: Weighing the evidence for sunspot cycles in fossil trees

Solar ghosts: Weighing the evidence for sunspot cycles in fossil trees

Solar ghosts: Weighing the evidence for sunspot cycles in fossil trees

Long droughts: Using natural climate archives to gage the risks of future “me...

Long droughts: Using natural climate archives to gage the risks of future “me...

Long droughts: Using natural climate archives to gage the risks of future “me...

Expecting the unexpected: The relevance of old floods to modern hydrology

Expecting the unexpected: The relevance of old floods to modern hydrology

Expecting the unexpected: The relevance of old floods to modern hydrology

What to expect when you’re expecting decadal variability in hydroclimatic pro...

What to expect when you’re expecting decadal variability in hydroclimatic pro...

What to expect when you’re expecting decadal variability in hydroclimatic pro...

Seeing the Forest for the Tree(Ring)s

Seeing the Forest for the Tree(Ring)s

Seeing the Forest for the Tree(Ring)s

The decadal character of northern California's winter precipitation

The decadal character of northern California's winter precipitation

The decadal character of northern California's winter precipitation

Resonate! How 90 Seconds of Cello Music Is Helping People Connect With Climat...

Resonate! How 90 Seconds of Cello Music Is Helping People Connect With Climat...

Resonate! How 90 Seconds of Cello Music Is Helping People Connect With Climat...

Absent rings are rare in Northern Hemisphere forests outside the American Sou...

Absent rings are rare in Northern Hemisphere forests outside the American Sou...

Absent rings are rare in Northern Hemisphere forests outside the American Sou...

GEOG5839.22, Paleofloods

GEOG5839.22, Paleofloods

GEOG5839.22, Paleofloods

GEOG5839.21, The Colorado River

GEOG5839.21, The Colorado River

GEOG5839.21, The Colorado River

Recently uploaded

1029-Danh muc Sach Giao Khoa khoi 6.pdf

1029-Danh muc Sach Giao Khoa khoi 6.pdf

1029-Danh muc Sach Giao Khoa khoi 6.pdf

Web & Social Media Analytics Previous Year Question Paper.pdf

Web & Social Media Analytics Previous Year Question Paper.pdf

Web & Social Media Analytics Previous Year Question Paper.pdf

psychiatric nursing HISTORY COLLECTION .docx

psychiatric nursing HISTORY COLLECTION .docx

psychiatric nursing HISTORY COLLECTION .docx

Sports & Fitness Value Added Course FY..

Sports & Fitness Value Added Course FY..

Sports & Fitness Value Added Course FY..

Advance Mobile Application Development class 07

Advance Mobile Application Development class 07

Advance Mobile Application Development class 07

Dr. Mazin Mohamed alkathiri

Unit-IV; Professional Sales Representative (PSR).pptx

Unit-IV; Professional Sales Representative (PSR).pptx

Unit-IV; Professional Sales Representative (PSR).pptx

VishalSingh1417

How to Give a Domain for a Field in Odoo 17

How to Give a Domain for a Field in Odoo 17

How to Give a Domain for a Field in Odoo 17

Seal of Good Local Governance (SGLG) 2024Final.pptx

Seal of Good Local Governance (SGLG) 2024Final.pptx

Seal of Good Local Governance (SGLG) 2024Final.pptx

Basic Civil Engineering notes first year Notes Building notes Selection of site for Building Layout of a Building What is Burjis, Mutam Building Bye laws Basic Concept of sunlight ventilation in building National Building Code of India Set back or building line Types of Buildings Floor Space Index (F.S.I) Institutional Vs Educational Building Components & function Sills, Lintels, Cantilever Doors, Windows and Ventilators Types of Foundation AND THEIR USES Plinth Area Shallow and Deep Foundation Super Built-up & carpet area Floor Area Ratio (F.A.R) RCC Reinforced Cement Concrete RCC VS PCC

Basic Civil Engineering first year Notes- Chapter 4 Building.pptx

Basic Civil Engineering first year Notes- Chapter 4 Building.pptx

Basic Civil Engineering first year Notes- Chapter 4 Building.pptx

Paris 2024 Olympic Geographies - an activity

Paris 2024 Olympic Geographies - an activity

Paris 2024 Olympic Geographies - an activity

Mattingly "AI & Prompt Design: The Basics of Prompt Design"

Mattingly "AI & Prompt Design: The Basics of Prompt Design"

Mattingly "AI & Prompt Design: The Basics of Prompt Design"

National Information Standards Organization (NISO)

Presentation by Andreas Schleicher Tackling the School Absenteeism Crisis 30 ...

Presentation by Andreas Schleicher Tackling the School Absenteeism Crisis 30 ...

Presentation by Andreas Schleicher Tackling the School Absenteeism Crisis 30 ...

Mehran University Newsletter Vol-X, Issue-I, 2024

Mehran University Newsletter Vol-X, Issue-I, 2024

Mehran University Newsletter Vol-X, Issue-I, 2024

Mehran University of Engineering & Technology, Jamshoro

Explore beautiful and ugly buildings. Mathematics helps us create beautiful d...

Explore beautiful and ugly buildings. Mathematics helps us create beautiful d...

Explore beautiful and ugly buildings. Mathematics helps us create beautiful d...

christianmathematics

Measures of Central Tendency: Mean, Median and Mode

Measures of Central Tendency: Mean, Median and Mode

Measures of Central Tendency: Mean, Median and Mode

Z Score,T Score, Percential Rank and Box Plot Graph

Z Score,T Score, Percential Rank and Box Plot Graph

Z Score,T Score, Percential Rank and Box Plot Graph

Unit-V; Pricing (Pharma Marketing Management).pptx

Unit-V; Pricing (Pharma Marketing Management).pptx

Unit-V; Pricing (Pharma Marketing Management).pptx

VishalSingh1417

Activity 01 - Artificial Culture (1).pdf

Activity 01 - Artificial Culture (1).pdf

Activity 01 - Artificial Culture (1).pdf

This PowerPoint helps students to consider the concept of infinity.

This PowerPoint helps students to consider the concept of infinity.

This PowerPoint helps students to consider the concept of infinity.

christianmathematics

PROCESS RECORDING FORMAT.docx

PROCESS RECORDING FORMAT.docx

PROCESS RECORDING FORMAT.docx

Recently uploaded (20)

1029-Danh muc Sach Giao Khoa khoi 6.pdf

1029-Danh muc Sach Giao Khoa khoi 6.pdf

1029-Danh muc Sach Giao Khoa khoi 6.pdf

Web & Social Media Analytics Previous Year Question Paper.pdf

Web & Social Media Analytics Previous Year Question Paper.pdf

Web & Social Media Analytics Previous Year Question Paper.pdf

psychiatric nursing HISTORY COLLECTION .docx

psychiatric nursing HISTORY COLLECTION .docx

psychiatric nursing HISTORY COLLECTION .docx

Sports & Fitness Value Added Course FY..

Sports & Fitness Value Added Course FY..

Sports & Fitness Value Added Course FY..

Advance Mobile Application Development class 07

Advance Mobile Application Development class 07

Advance Mobile Application Development class 07

Unit-IV; Professional Sales Representative (PSR).pptx

Unit-IV; Professional Sales Representative (PSR).pptx

Unit-IV; Professional Sales Representative (PSR).pptx

How to Give a Domain for a Field in Odoo 17

How to Give a Domain for a Field in Odoo 17

How to Give a Domain for a Field in Odoo 17

Seal of Good Local Governance (SGLG) 2024Final.pptx

Seal of Good Local Governance (SGLG) 2024Final.pptx

Seal of Good Local Governance (SGLG) 2024Final.pptx

Basic Civil Engineering first year Notes- Chapter 4 Building.pptx

Basic Civil Engineering first year Notes- Chapter 4 Building.pptx

Basic Civil Engineering first year Notes- Chapter 4 Building.pptx

Paris 2024 Olympic Geographies - an activity

Paris 2024 Olympic Geographies - an activity

Paris 2024 Olympic Geographies - an activity

Mattingly "AI & Prompt Design: The Basics of Prompt Design"

Mattingly "AI & Prompt Design: The Basics of Prompt Design"

Mattingly "AI & Prompt Design: The Basics of Prompt Design"

Presentation by Andreas Schleicher Tackling the School Absenteeism Crisis 30 ...

Presentation by Andreas Schleicher Tackling the School Absenteeism Crisis 30 ...

Presentation by Andreas Schleicher Tackling the School Absenteeism Crisis 30 ...

Mehran University Newsletter Vol-X, Issue-I, 2024

Mehran University Newsletter Vol-X, Issue-I, 2024

Mehran University Newsletter Vol-X, Issue-I, 2024

Explore beautiful and ugly buildings. Mathematics helps us create beautiful d...

Explore beautiful and ugly buildings. Mathematics helps us create beautiful d...

Explore beautiful and ugly buildings. Mathematics helps us create beautiful d...

Measures of Central Tendency: Mean, Median and Mode

Measures of Central Tendency: Mean, Median and Mode

Measures of Central Tendency: Mean, Median and Mode

Z Score,T Score, Percential Rank and Box Plot Graph

Z Score,T Score, Percential Rank and Box Plot Graph

Z Score,T Score, Percential Rank and Box Plot Graph

Unit-V; Pricing (Pharma Marketing Management).pptx

Unit-V; Pricing (Pharma Marketing Management).pptx

Unit-V; Pricing (Pharma Marketing Management).pptx

Activity 01 - Artificial Culture (1).pdf

Activity 01 - Artificial Culture (1).pdf

Activity 01 - Artificial Culture (1).pdf

This PowerPoint helps students to consider the concept of infinity.

This PowerPoint helps students to consider the concept of infinity.

This PowerPoint helps students to consider the concept of infinity.

PROCESS RECORDING FORMAT.docx

PROCESS RECORDING FORMAT.docx

PROCESS RECORDING FORMAT.docx

GEOG5839.15, signal processing

1. October 18 30 the ‘detrended’ ring-width Signal processing I The linear aggregate model of tree growth index

2.

3. DOWNLOAD THESE DATA Cat Mesa (NM556) Fenton Lake (NM550) Abouselman Spring (NM555) Rito de los Frijoles (NM501) Baca (NM558) Los Alamos New Mexico (NM046)

4. h p://www.ldeo.columbia.edu/tree-ring-laboratory/resources/so ware

5. TREE-RING WIDTH DATA pith bark

6. THE PRINCIPLE OF AGGREGATE TREE GROWTH Rt = At + Ct + δD1t + δD2t + Et

7. THE PRINCIPLE OF AGGREGATE TREE GROWTH Rt = At + Ct + δD1t + δD2t + Et size-related growth trend caused by physiological aging

8. At does not have a universal or predictable shape.

9. STANDARDIZATION

10. the ‘detrended’ ring-width index

11. ARSTAN autoregressive standardization

12. PROGRAM ARSTAN PRODUCES CHRONOLOGIES FROM TREE-RING MEASUREMENT SERIES BY DETRENDING AND INDEXING (STANDARDIZING) THE SERIES, THEN APPLYING A ROBUST ESTIMATION OF THE MEAN VALUE FUNCTION TO REMOVE EFFECTS OF ENDOGENOUS STAND DISTURBANCES.

13.

14. DIVIDE (A) the raw ring-width data by (B) the ‘detrending’ curve

15.

16.

17.

18.

19.

20. ARSTAN OUTPUT

21.

22.

24.

25.

26.

27. EXERCISE Use several diﬀerent detrending methods to standardize our set of ring-width chronologies and let’s see what happens!

28. STANDARDIZE THESE DATA Cat Mesa (NM556) Fenton Lake (NM550) Abouselman Spring (NM555) Rito de los Frijoles (NM501) Baca (NM558) Los Alamos New Mexico (NM046)

29.

30. USE FOUR DIFFERENT APPROACHES TO STANDARDIZATION Horizontal line Negative exponential curve 20-yr ﬂexible spline Flexible spline set to 67% of series length

31.

32. GEOG5839 XT C L AS S NE WHO WILL FIND THE FIRST “DIRTY DOG”? Source: Terry Bain