Workshop on
Climate and Cultural History in the Americas
Centro Ecológico de Akumal
Quintana Roo, México
March 31–April 2, 2005
Workshop on
Climate and Cultural History in the Americas
Centro Ecológico de Akumal
Quintana Roo, México
March 31–April 2, 2005
Agenda
Thursday March 31, 2005
09:00 Meeting Registration (pick up name badges, etc.)
09:25 Welcome and Introductions
What does the climate record tell us?
09:45 Paleoclimate records from the southern Maya Lowlands – Mark Brenner
10:10 Paleoclimate of the Yucatan Peninsula from lake sediment cores and speleothems: Implications for Maya cultural transformations – David Hodell
10:35 Spatial patterns of decadal drought and wetness regimes over western North America during the past 1200 years – Dave Stahle
11:00 Coffee Break
11:30 Climate variability in central Mexico for the last 800 years – José Villanueva-Díaz
11:55 The curse of climate: Records of drought and famine in Central Mexico – Matt Therrell
12:20 Lunch
14:00 Deciphering recent climate change in central Mexican lake records – Sarah Metcalfe
14:25 Site climatic sequence congruencies in Yucatan? Paleoclimatic and archaeological implications – Lewis (Skip) Messenger, Jr.
14:50 Possible solar signals in historical droughts in Central and Southeastern Mexico – Blanca Mendoza
15:15 Coffee Break
15:45 Has solar forcing been an important influence on climate in the late Holocene? – Ray Bradley
16:10 Relevance of long (thousand-year) climate model simulations for evaluating the impact of extreme climate regimes on societies in the Americas – Caspar Ammann
16:35 Abrupt climate changes in Medieval western North America – Nick Graham
17:00 Linking vegetation and climate change in northern South America during the Late Holocene – Konrad Hughen
17:25 A 6,000-year record of drought in north-central Washington State from laminated lake sediments – Mark Abbott
17:50 Adjourn for the day
Friday April 1
Climate and Cultural Responses
09:00 Volcanism and Mesoamerican archaeology – Richardson Gill & Jerome Keating
09:25 Snakes of water and sterile years”: anomalous weather and social responses in colonial Mexico – Georgina Endfield
09:50 Deadly deluges and shattered landscapes: El Niños and earthquakes on the Andean Coast – David Keefer
10:15 Drought-induced migrations of pre-Hispanic native Americans – Larry Benson
10:40 Coffee Break
11:10 Geographic patterns of epidemics in Mexico – Rodolfo Acuña-Soto
11:35 Historical climate variability, climatic hazards, and societal impacts of the Southeast United States – Cary Mock
12:00 Evidence of extreme climatic events in the Americas from Spanish archives – Ricardo García-Herrera
12:25 Lunch Break
14:00 Looking for ENSO signals in the past: Natural disasters, impacts and cultural responses in some regions of South America during the XVII, XVIII and XIX centuries – Maria del Rosario Prieto
14:25 Chronology of the presence of El Niño phenomenon in Mexican history (XVI-XIX century): An adapatation – Leticia González
14:50 Decadal anomalies of rainfall and temperature in the Yucatan Peninsula for the twentieth century – Roger Orellana
15:15 Coffee Break
15:45 Adaptive cultural strategies, climate variability and ENSO in Mexican History – Virginia García Acosta
16:10 Climate, risk, and history: Are the lessons learned? – Roger Pulwarty
16:35 Cycles of social and environmental complexity in lowland Latin America – George Gumerman
17:00 General comments & Adjourn for the day
Saturday April 2
Discussion of future collaborative work and prioritizing of research agendas
09:00 Proxy Records — Dave Stahle and Mark Brenner
09:30 Historical/Cultural Records — Virginia Garcia-Acosta and George Gumerman
10:00 Future Steps & Funding Opportunities — Ray Bradley and Roger Pulwarty
10:30 Final Remarks — Henry Diaz
10:45 Workshop Ends
A 6,000-year record of drought in north-central Washington State
from laminated lake sediments
Mark B. Abbott and Daniel B. Nelson Department of Geology and Planetary Science, University of Pittsburgh, 4107 O’Hara Street, SRCC Building Room 200, Pittsburgh, PA, 15260
Bruce P. Finney Institute of Marine Science, University of Alaska, Fairbanks AK 99775
The Pacific Northwest is prone to multi-decadal droughts that have serious economic impacts on the natural resources of the region including forestry, fisheries and water resources. Although this region is not generally considered to be arid, much of it is, and the population is currently expanding at a very rapid rate and taxing the limited the water resources between a multitude of uses including municipal, agricultural, and hydropower. Drought in this region has been linked with the warm phase of the Pacific Decadal Oscillation (PDO). Knowing the long-term history of drought would give us with an improved ability to predict their timing and severity, but historic records of climate are too brief to provide such an understanding. In order to place current events in the context of the natural variation of the past, we are working to produce a multiproxy study using laminated lake sediments to investigate the complex relationships between large-scale climatic forcing, regional climatic change, and vegetation and lake response at a watershed-scale from multiple sites.
In light of extended ~5-year drought conditions that currently affect much of western North America, substantial effort has been focused on understanding the natural cyclicity and magnitude of such events from the paleoclimate record. Here we present a ~6,000-year record of drought variability with ~5-year resolution based on a multiproxy study including oxygen/carbon isotopes and sediment grayscale analyses from Castor Lake in north-central Washington State. The grayscale record correlates well (r2 = 0.75) with the ~1500-year Palmer Drought Severity Index (PDSI) reconstructed from tree-ring data across the west. This serves to validate the legitimacy of both methodologies and allows for confident interpretation of the period for which only lake data are available. Spectral analyses of the ~6,000-year record from Castor Lake reveals a strong and dominant periodicity centered on ~50-years. Such timescales are coincident with those observed in Pacific Ocean variability, and suggest that the PDO may have exerted an influence on regional drought patterns for at least the past ~6,000 years.
The Most Important Epidemics and Famines in the Valley of Mexico in the Last 1000 Years
Rodolfo Acuña-Soto
Departamento de Microbiología y Parasitología,
Facultad de Medicina, Universidad Nacional Autónoma de Mexico.
The valley of Mexico, once surrounded by densely forested mountains and covered with great lakes, rich soil and with a benign climate has been a preferred population center for millennia. As result of political centralism and other favorable conditions, the area in now the largest human conglomerate in human history. This situation did not result from a continuous period of prosperity and stability. On the contrary, the population dynamics has been unstable for the last 1 000 years due to periods of high mortality. The megacity of today was founded in the year of 1325 in the same valley were cities such as Teotihuacan and Tula collapsed long time ago, probably victims of drought, war, famine epidemics and social unrest. In its short history of 675 years, the population of Mexico City and the valley went through several calamitous periods of high mortality due to famines and epidemics. Some epidemics killed up to 80% of the entire population in only two or three years, the last event of an epidemic with high mortality occurred 87 years ago, when the Spanish flu of 1918 took over 10% of the population. Based in these events, and because of the recent trends in climatic change and emerging infectious diseases, the reevaluation of the history of epidemic disease and famine in the Valley of Mexico is necessary. However, until now, the formal study of famines and catastrophic epidemics in Mexico has been primarily descriptive and remains largely incomplete.
For this study a review of the previous published chronologies of epidemics and famines was performed. This was complemented with a multi-year review of all documentation available in historical descriptions, chronicles, old medical books, diaries, newspapers and official documentation about epidemics and famines available in archives and libraries in Mexico and United States.
Six epidemiological periods and five transitions were identified in the record. The first epidemiological period correspond to the pre-Hispanic epoch, when massive mortality was associated to famines and large outbreaks of unidentified diseases. These epidemics and most famines were invariably associated to severe drought. The second period and first transition is clearly marked by the arrival of the Spanish to Mexico, the then emerging infectious diseases smallpox, mumps, chickenpox and measles initiated their cycles of epidemics and endemicity in Mexico. Invariably, the first events of these diseases were catastrophic for the Indian population. This process lasted only from 1520 to the middle of the 16tth century. The second transition and third period began with the emergence of drought-associated epidemics of hemorrhagic fevers in 1545. The 22 epidemics of hemorrhagic fevers caused a major population collapse with few parallels in human history. This period ended around 1815 when the hemorrhagic fevers mysteriously disappeared. In this third epidemiological period, typhus started to appear sporadically. The third transition and fourth period began approximately in 1815. During this time typhus became a major epidemiological force in the area, the end of this period came in 1915 when the last large epidemic of typhus occurred. The fifth period comprises from 1915 to 1982, when most infectious diseases declined thanks to vaccines and sanitary measures. The last transition in 1982 led to the sixth and actual period is characterized by the emergence of AIDS, antibiotic resistance and a myriad of other new and old infectious diseases. This period is also characterized by the growth of the older population and extensive urbanization. This is being reflected by the increase in the number of deaths due to pneumonia, a trend that is seasonal and is clearly increasing.
The analysis of the data from 1 000 years revealed a total of 122 major epidemics and 19 historic famines. Drought was clearly associated to 47 (38.5%) of all epidemics, mainly typhus and hemorrhagic fevers. Typhus and war were regular companions during the 19th century when both were very common. Severe weather conditions such as drought or frost in late spring of early fall was the cause of all 19 famines; only three famines were associated to epidemics. During the pre-hispanic period, a total of 12 famines were registered, the frequency diminished until 1786. Of course, periods of food scarcity were registered after that year, as during the Mexican Revolution, however, none of these periods compare with the magnitude of the great famines. A total of 18 infectious diseases were identified, they originated 122 sudden and extensive epidemics. Of those 122 epidemics, 109 (89.3%) were caused by a single disease, 13 (10.6%) by two etiological agents and four epidemics (3.2%) were caused by three simultaneous diseases.
Transmission by aerosols from person to person was the preferred mechanism of contagion. Nine of the 18 different diseases were transmitted by droplets, accounting for 71 cases or 58% of all epidemics. Insect vectors (typhus and malaria) represented 21% of all epidemics and waterborne diseases (cholera, typhoid fever and poliomyelitis) accounted for 9% of the epidemics. Interestingly, almost all the diseases that cause sudden and extensive mortality in the Valley of Mexico do not have reservoirs in nature, they correspond to exclusive human diseases. Seven diseases were emerging infectious diseases of their respective time, all of them were imported: AIDS, chickenpox, cholera, measles, mumps, smallpox, and influenza. The hemorrhagic fevers, of unknown etiology, reemerged locally from a distant past.
Local and global epidemiological changes result from four driving forces. First, connectivity that allows the transport of a pathogen from its natural habitat to a new place, such as the West Nile virus. Second, genetic change that results from mutation or recombination, for example, the formation of new flu strains or the emergence of antibiotic resistance in bacteria. Third, human variables as population density age structure, nutrition, mobility, water supply and specific habits. Fourth, climate change, this can have multiple effects such as increasing the frequency or geographic extension of climate-dependent seasonal diseases (malaria, dengue, diarrhea, yellow fever etc). Alternatively extreme climatic conditions can force the conditions for famine, or the sudden outbreak of drought-associated diseases as the historic hemorrhagic fevers in Mexico of hantavirus. Today all these forces remain active, the high population densities in the valley of Mexico, the world interconnectivity, active genetic recombination of some viruses, the aging population and an historic background of diseases transmitted by aerosols make diseases as SARS and avian influenza serious threats to densely populated areas around the world.
Relevance of long (thousand-year) climate model simulations for evaluating the impact of extreme climate regimes on societies in the Americas
Caspar Ammann
National Center for Atmospheric Research – Climate and Global Dynamics Division
Climate Change Research Section
1850 Table Mesa Drive, Boulder, CO 80307-3000
ammann@ucar.edu http://www.cgd.ucar.edu/ccr/ammann
Coupled modeling of the global climate system without the need of flux corrections is now about 10 years old. The quality of the simulations have improved significantly in this time, both in terms of how they can resolve key processes as well as in the way how realistically the models are now routinely being forced. The horizontal, and to some extent the vertical resolution was increased, which has led to significant improvements in the representation of regional climate features. Does that mean that these simulations are now directly applicable to climate studies of the Americas? Can we even expect that a simulation forced with the best estimates of external forcings indeed can reproduce the climate of the Americas?
For understanding regional climate variations, two critical aspects of the climate system need to be considered: First, stochastic aspects might dominate this highly non-linear system with numerous states for its mean as well as for its preferred modes of variability. Such a system can exhibit extreme conditions that sometimes are extensive in time. The ‘driver’ behind any such condition would be internal variability alone. In order to reproduce such conditions in a coupled climate model, long integrations or multi-ensembles starting from varying initial conditions can be performed. Particularly long integrations with fixed forcings offer some insight into occurrence intervals, often described now in probabilistic terms. However, generally, this is an over-simplification of the system, as the real world is never really in an equilibrium and thus a pure internal variation as such does probably not exist. Any ‘purely internal component’ of the climate system is somewhere connected to the rest. Thus, as a second approach, modeling studies have started to focus on long transient simulations that contain realistic external forcings. This approach leads to a climate system behavior better reflecting overall characteristics of the real world. But which parts of the real world climate history can one expect such a model to (more or less) adequately reproduce, even if the model were a perfect model? Would one require ensemble simulations to improve the probabilistic measures for linking a particular forcing to a desired response? Is the right background climate required for studying unforced climate variations? What can we learn in this regard from currently available unforced and forced thousand-year long coupled simulations? What is missing in terms of forcings and resolved feedbacks? What improvements can we expect from the next generation of models that will include interactive vegetation, the capability to prescribe transient landuse changes and interactive mineral dust are going to be interacting with in a fully coupled carbon cycle? These questions are addressed first in more general terms but then with a special emphasis on the climate history of the Americas.
Drought-induced migrations of pre-Hispanic Native Americans
Larry Benson
U.S. Geological Survey
Boulder, CO 80303-1066
Prior to 1140 A.D., the Native American population of the Four Corners region was on the rise as evidenced by increase in multi-room structures (great houses). A persistent drought occurred throughout the Four Corners region between 1140 and 1165 A.D. and also throughout much of the western United States. This drought caused migration of Native Americans to wetter areas and resulted in the abandonment of the relatively dry central San Juan Basin by the Anasazi. Great House construction and modification in Chaco Canyon, New Mexico, ceased abruptly at 1130 A.D.
Another severe drought occurred between 1275 and 1310 A.D., resulting in the complete abandonment of the San Juan Basin and movement of many of the Anasazi people to the Rio Grande region (numerous Pueblos) northeastern Arizona (Hopis), and west central New Mexico (Zuni and Acomas).
Both these droughts appear to involve the weakening or cessation of the summer monsoon. This factor was sufficient to impact agriculture, especially the growing of maize which is dependent on summer moisture. In Utah the Fremont people abandoned many of their settlements during the first drought and the Fremont who inhabited marshlands along the eastern shore of Great Salt Lake ceased consumption of maize at ~1150 A.D., returning to a reliance on wild foods.
One of the regions in the San Juan Basin that was dependent on maize was Chaco Canyon. We have used what we know about the hydrology and soils of the canyon to estimate how many people could have been supported by its agricultural productivity. These calculations indicate that the canyon could have supported only a few hundred of the 2000 to 10,000 people estimated to have lived in it, necessitating the importation of foodstuffs.
The strontium-isotope and trace-element ratios of archeological corn cobs from the Pueblo Bonito great house were compared with the chemistry of synthetic soil waters from potential agricultural field sites in the San Juan Basin to determine the source of imported corn. The data indicate that the corn was grown either in the Newcomb area 80 km to the west of Chaco Canyon or in side-tributary sites located northwest and downstream of Chaco Canyon.
Has solar forcing been an important influence on climate in the late Holocene?
Raymond S. Bradley
Climate System Research Center
University of Massachusetts
Amherst, MA 01003-9297, U.S.A.
There is an extensive literature going back many decades describing supposed links between weather and solar activity (mainly sunspots). However, most of these studies do not stand up to careful scrutiny. Furthermore, they lack an explanation for the causes or mechanisms that might link solar irradiance to the earth’s atmosphere. Recently, a number of empirical studies have attempted to link changes in total solar irradiance during recent decades to changes in patterns of global cloudiness, or to circulation changes associated with variations in the ultra-violet part of the solar irradiance spectrum, which affects the stratosphere. Several general circulation and global energy balance models have been used to assess these possible effects on global and regional climate. The models suggest that climate effects are possible, even with relatively small changes in total irradiance. Furthermore, general circulation models indicate that there are distinct changes in circulation which lead to regional patterns of climate change, rather than simply overall warming or cooling. There have also been a number of paleoclimatic studies linking past changes in climate to solar forcing. In the context of this meeting, the most relevant is the link that has been made between solar activity, regional drought and the Classic Mayan collapse.
Here, I examine evidence, from a variety of sources around the world, to identify the signal of solar activity in past climate changes. Surprisingly, there is a fairly coherent pattern of climate change associated with solar activity changes during the Holocene. Periods of low solar activity are generally associated with lower temperatures at mid to high latitude sites, and with weaker monsoon activity in the Tropics. However, it must be recognized that most studies do not recognize any link with solar forcing, so there is a distinct danger of the “reinforcement syndrome”, whereby only a very small number of well-publicized studies establish a paradigm that may not be supported by the majority of data. Much more research is needed to fully determine whether solar forcing has played an important role in past climate changes. A well-designed strategy, using a network of high-resolution proxies, is needed to do this.
Paleoclimate records from the southern Maya Lowlands
Mark Brenner
David A. Hodell
Jason H. Curtis
Department of Geological Sciences &
Land Use and Environmental Change Institute
University of Florida
Gainesville, Florida USA 32611-2120
Over the past ~50 years, paleolimnological techniques have been used to explore the environmental history of the Maya Lowlands in Peten, northern Guatemala. In the 1970s, the interdisciplinary Central Peten Historical Ecology Project, under the direction Edward S. Deevey, combined archaeological results from drainage basin surveys with geochemical and palynological data from lake sediment cores to assess long-term human impacts on lowland tropical karst watersheds. Long cores from deep lakes extended into the late Pleistocene and showed a transition from cool, dry late-Glacial conditions to a warmer, moister early Holocene ca. 10,000 years ago. Pollen evidence demonstrated that the tropical dry forests that characterize the region today were absent during the Pleistocene. High forest prevailed in the Holocene for more than six millennia before beginning to decline about 3,500 yr BP. Loss of forest taxa and replacement by grasses, weeds, and maize, was attributed wholly to human activity. Increased sedimentation during the episode of forest disappearance was interpreted to be a consequence of soil erosion that accompanied land clearance for agriculture and construction.
Recent studies of lake cores from locations in northern Yucatan, northern South America, and marine and island sites in the Caribbean, indicate regional drying in the latter part of the Holocene, starting before 3,000 yr BP. Widespread drying, perhaps related to the position of the ITCZ, could also have played a role in vegetation changes in Peten. Long-term human activity in Peten watersheds, however, confounds paleoclimatic interpretation of records derived from pollen. Alternative climate proxies such as stable oxygen isotopes and compound-specific carbon isotopes are being used to test paleoclimate inferences based on pollen. These proxies may also be influenced indirectly by human activities, compromising paleoclimate inferences in the late Holocene portion of Peten lake sediment records. Alternative sources of regional climate information, such as speleothems, tree rings, and corals may prove helpful in distinguishing between natural climate variability and human-mediated impacts on the Peten environment.
“Snakes of water and sterile years”: Anomalous weather and social responses in colonial Mexico
Georgina H. Endfield
School of Geography, University of Nottingham
University Park, Nottingham
United Kingdom NG7 2RD
There is growing concern over the impacts of year-to-year climate variability and anomalous and ‘extreme’ weather events such as droughts, floods, hurricanes and unusually high or low temperatures. Such events can have, and have had in the past, the greatest and most immediate social and economic impacts and repercussions of all climate changes. The response of human activities and the natural environment to past episodes of anomalous weather provides a guide to where the most critical sensitivities to future events may lie. Reconstructing climate histories and investigating the impacts of and social responses to extreme weather events in the past should thus be seen as critical steps if we are to understand and anticipate the potential repercussions of future events. Historical documents represent invaluable sources in this respect.
Severe and prolonged droughts, catastrophic floods and hurricanes have affected Mexico’s population throughout history and prehistory. The country’s rich colonial archives represent one of the most important resources for investigating the impacts of such events in the past. In this paper, I hope to demonstrate the potential of these sources for identifying periods of severe or prolonged anomalous weather between 1550 and 1821 and to illustrate how these documents can provide invaluable insight into the social, economic and demographic impacts and responses engendered therein. The study is concerned with four case study regions in Mexico, covering a range of climatic, environmental, socio-economic, and political contexts and histories: Chihuahua in the north, Oaxaca in the south, Michoacán, in the central highlands and Guanajuato in the Bajío (‘lowlands’) of the north central highlands. Attention focuses on regionally specific weather events as well as episodes of anomalous weather that appear to have been coincident in all of the case study areas. The relationship of some of these identified episodes to the El Niño Southern Oscillation phenomenon will be explored and a number of key phases of widespread agrarian crisis that may have been stimulated or triggered by unusual or anomalous weather will be examined. Throughout, I hope demonstrate how the features of a society influenced the way a particular weather event was experienced, how its impacts were distributed across different sectors of that society and how different groups of people responded to and coped with its repercussions.
Adaptive cultural strategies, climate variability and ENSO in Mexican history
Virginia García-Acosta
Center for Research and Higher Studies in Social Anthropology (CIESAS)
Mexico, D.F.
Disasters are social processes resulting from pre-existing critical conditions in which certain natural hazards play a role. The need to distinguish between natural phenomena or hazards and disasters is an inevitable starting point, mainly when we are interested in understanding what is called the social construction of risks. Research on these topics has shown the magnitude and severity of accumulated social and economic vulnerabilities, the social construction of risks, associated with the presence of a severe natural hazard result in real disasters.
People and communities all over the world have historically formulated cultural constructions to confront real and potential disasters. Societies are not and have never been simple passive actors in face of disasters, either in respect of response or in formulating the concept of disaster itself. Such cultural constructions are part of the everyday life of certain societies or certain sectors of societies and as such need to be understood, considered and explained.
Adaptive strategies are part of these cultural constructions that a group, a community and generally speaking an entire society adopts and adapts in order to cope with disaster. Analysis of adaptive strategies diachronically and comparatively, allows us to understand the specificity of the disaster.
In this paper and stemming from historical and anthropological perspectives based mainly in Mexican, and some other Latin American cases, adaptive strategies to disasters as cultural constructions and their relation to climate variability and ENSO will be explored.
Evidence of extreme climatic events in the Americas from Spanish Archives
Ricardo García-Herrera
Dto. Física de la Tierra II, Facultad de Ciencias Físicas
Universidad Complutense de Madrid, Ciudad Universitaria
28040 Madrid, Spain
Spanish historical archives contain a vast store of information about Spain and its former colonies in America and Asia. Some searches for climate-related information within these archives have been undertaken recently, but they have been by no means exhaustive. This paper discusses the principal archives and shows, by means of several examples, that they exhibit a high potential for inferring past climate over a wide range of time scales and geographical areas. This presentation will be focused on our latest results. I will show new evidences on hurricanes in the Caribbean and Pacific basins and their impact on coastal areas, I will discuss how logbooks records can be used to obtain climatic databases and their applicability to extreme events such as low latitude icebergs sightseeing. Extraction of such information is time consuming, and requires a combination of archival, historical and climatological expertise, and the development of individualized methodologies to fit each situation and type of data.
In spite of these difficulties, the archives can be a particularly useful source in many cases where there are no alternative sources of climate data. Thus, the complexities of the multidisciplinary effort required should not discourage other researches from undertaking similar studies.
Volcanism and Mesoamerican archaeology
Richardson B. Gilla and Jerome P. Keatingb
a7707 Broadway 11A, San Antonio, TX 78209-3250, USA
bDivision of Management and Marketing, The University of Texas at San Antonio, San Antonio, TX 78249-0634, USA
Abstract
Drought and drought-induced famine are recurring phenomena in Mesoamerica that have devastated populations in the region repeatedly during the past two millennia. Although it is counterintuitive to conceive of the idea that volcanic eruptions anywhere in the world might affect the lives of people in Mesoamerica, we examine the reports of drought and famine during the period A.D. 1440 to 1840 and compare them with known, large volcanic eruptions. We then apply non-parametric statistical techniques to determine whether the coincidences seen between worldwide volcanic eruptions and Mesoamerican drought within the following two years were due to random chance or whether there was a direct, mathematically verifiable correlation. We find a direct correlation to a probability of 56 in 100 million. We conclude that due to its unique geographical position, Mesoamerica was repeatedly devastated by drought and subsequent famine between 1440 and 1840 due to the indirect climatic effects of large volcanic eruptions that could be located anywhere in the world.
Chronology of the presence of El Niño phenomenon in Mexican history
(XVI-XIX Century): An adaptation
Leticia González Álvarez
Escuela Nacional de Antropología e Historia
El Niño phenomenon is 5,000 years old, geologists and palaeontologists have found in soil layers evidences of old pluvial and alluvial flows. Recently sciences are more interested in climate historical evidences. In Mexico there is not much historical information of this kind. With the exception of some documents that refer to droughts and floods, there are not good documented references with qualitative data related to El Niño phenomenon occurrence that may show social effects in a historical moment a place. This lack of information was a motivation to propose a chronology of the presence of El Niño phenomenon in the Mexican history from the XVI to XIX century.
A starting point for the historical tracking of El Niño in Mexico was the chronology of Quinn and Neal (1992) and the work of Ortlieb (1995). These authors were the first to explore through history registered climatic events in the Pacific Ocean from the beginning of the Spanish conquest to present time. Following this line of research, which combines contemporary information and historical sources, was analysed the Desastres agrícolas en México. Catálogo Histórico (Historical Catalogue of Agricultural Disasters in Mexico, 2003), which goes from the year 958 up to 1900. The purpose of this analysis was to identify indicators that show social impacts in connection with El Niño-related climate anomalies, like extreme droughts and floods. The information obtained out from this analysis is mainly qualitative, and it allows us to improve our knowledge about previous researches, mainly done with instruments.
This paper is part of the thesis “El Niño perdido en la Historia de México. Búsqueda desde una óptica multidisciplinaria” and presents a methodological contribution to the investigation of the past events of El Niño in Mexican history.
Abrupt climate change in Medieval Western North America
Nicholas Graham Hydrologic Research Center, 12780 High Bluff Drive, Suite 250 San Diego, CA 92130-2069
Malcolm Hughes Laboratory of Tree Ring Research, University of Arizona Tucson, AZ 85721
Kim Cobb Georgia Institute of Technology, Atlanta, GA 30332-0340
Caspar Ammann National Center for Atmospheric Research, Boulder, CO 80307
The increasing number of available proxy records is allowing a more detailed portayal of the evolution of Late Holocene (during the last 2000 yrs) climate over the parts of the western US. Rather than showing smoothly varying changes, the picture that emerges (though by no means clear or unambiguous) is one of sharp swings that appear to have linkages to variability in tropical Pacific SSTs (see discussions in Cobb et al., 2003; Cook et al., 2004). The potential societal vulnerability to rapid, non-anthropogenic, climate change suggested by this idea emphasizes a need to better quantify the related evidence.
Among the intriguing episodes during this period are the two period of severe droughts that occurred 700–1100 yrs BP as documented by Stine (1994) on the basis drowned trees marking low stands of Mono Lake and other regional proxy records. Tree-ring reconstructions of drought-stress (Cook et al., 1999, 2004) support the timing of these droughts. We attempt to reconstruct Mono Lake inflow, which arises largely from Sierra Nevada snowmelt, based on the relationships between the tree-ring based reconstructions and modern precipitation records. These proxy-based inflow records are then used to drive a water balance model (an emulation of that described by Vorster, 1984). Results using a very simple model for reconstructing inflow from the tree-ring data reproduce the timing of the droughts well, though the reductions in lake levels are somewhat smaller than those recorded by Stine (1994). Slight changes in the reconstruction method bring the simulated and proxy-inferred lake stages into good agreement.
The talk will give a synopsis of proxy-inferred Medieval and Little Ice Age climate swings over the western US (including the Mono Lake modeling) results, and examine the evidence (including results from AGCM experiments) that these shifts resulted from changing tropical Pacific SSTs.
References
Cobb, K. M., C. D. Charles, H. Cheng, and R. L. Edwards, 2003: El Niño/Southern Oscillation and tropical Pacific climate during the last millennium, Nature, 424, 271-276.
Cook, E. R., D. M Meko, D. W. Stahle, and M. Hughes, 1999: Drought reconstructions for the Continental United States, J. Clim., 12, 1134-1144.
Cook, E. R., C. Woodhouse, C. M. Eakin,and D. M. Meko, 2004: Long-Term Aridity Changes in the Western United States, Science, 306, 1015-1018.
Stine, S., 1994: Extreme and persistent drought in California and Patagonia during Medieval time, Nature, 369, 546-549.
Workshop on
Cycles of Social and Environmental Complexity in Lowland Latin America
George J. Gumerman
School of American Research & The Santa Fe Institute
Santa Fe, NM
The goal of this workshop is to catalyze a fresh look at the question of long-term cycles in complexity in the tropics of social and environmental change and the relationship between the two. We will bring together four different groups of scholars:
· Ecologists and climatologists engaged in quantitative studies of anthropogenic change in the tropics
· Archaeologists interested in the relationship between social and environmental change through time in lowland Latin America
· Researchers with expertise in transdisiplinary theory and mathematical modeling
· Policy makers who are interested in the results of the research for establishing future policy
With this workshop, we will begin a program of cross-disciplinary conversations on anthropogenic change in the tropics. Within this broad framework, we intend to pursue several more specific themes. These themes emerge from archaeological discoveries in lowland Latin America: the relationship between the constraints and opportunities provided by biophysical environments and cycles of social complexity. We will focus on three geographic cases: the tropical and subtropical rainforest of the Amazon, the somewhat dryer lowlands of Central America, and the rich estuarine and lagoon environments of the Brazilian coast. The temporal span of our interest is three periods: the prehistoric situation, the period of European contact, and the contemporary situation.
Clearly the questions we ask have important ramifications for the current development of Latin American lowlands and the formulation of resource management and social policy. In the workshop’s three regional contexts, former stereotypes of a pre-contact pristine rainforest have given way to a landscape substantially modified by cultural factors that shaped the natural world. Evidently, the landscape can no longer be understood solely in terms of natural processes, but must include historical cultural factor.
Paleoclimate of the Yucatan Peninsula from lake sediment cores and speleothems: Implications for Maya cultural transformations
Hodell, D.A., Brenner, M., Curtis, J.H.
University of Florida, Department of Geological Sciences
PO Box 12120, Gainesville, FL 32611
One of the more controversial results of paleoclimatic studies on the Yucatan Peninsula has been evidence for a protracted drought during the Terminal Classic Period (ca. 800 to 1050 A.D.), which coincided with the demise of Classic Maya civilization. The clearest evidence for the Terminal Classic drought (TCD) comes from the study of sediment cores in Lake Chichancanab in north central part of the Yucatan Peninsula. The characteristics that make this lake system especially sensitive to paleoclimate change include its effectively closed hydrology, saturation for gypsum (CaSO4), high carbonate microfossil abundance, and relatively low-density prehistoric occupation of its watershed. Sediment cores from deep water indicate that the TCD consisted of a series of dry events separated by intervening periods of relatively moister conditions. An early phase of gypsum deposition lasted from ~770 to 870 AD and a late phase from ~920 to 1100 AD. Each dry phase is represented by multiple gypsum (density) bands interbedded with organic-rich sediment that indicate alternating dry and wet conditions. The intervening 50-year period (ca. 870 to 920 AD) was relatively moist and sediments were dominated by organic matter. A d18O record from Lake Punta Laguna in northeastern Yucatan shows two increases in d18O during the Terminal Classic Period, from ~750 and 850 AD and ~910 to 990 AD, supporting the two-phase subdivision of the TCD inferred from Lake Chichancanab density records.
Results from lake sediment cores in the southern lowlands have yielded ambiguous results regarding the TCD, but human disturbance of Peten watersheds complicate paleoclimatic interpretations. No evidence for a TCD has yet been found in northwestern Yucatan; instead, a record from Aguada X’caamal shows an important climate change in the fifteenth century A.D. associated with the start of the Little Ice Age. Do these disparate results reflect real subregional differences in the climate history of the Yucatan Peninsula during the Terminal Classic Period or do the differences result from non-climatic effects on lacustrine d18O signals? We propose this question may be addressed by comparing lake sediment core d18O records with similar analyses of oxygen isotopes in speleothems. Results of a preliminary pilot study of a stalagmite from a cave near Hobonil, Mexico, demonstrate the potential of speleothem paleoclimatology in the Maya lowlands.
Linking vegetation and climate change in northern South America during the Late Holocene
Konrad Hughen, Pascale Poussart and Nick Drenzek
Department of Marine Chemistry and Geochemistry,
Woods Hole Oceanographic Institution,
Woods Hole, MA, USA
Abstract
Certain classes of organic compounds that are sequestered in sediments can be traced directly to specific sources, such as epicuticular leaf waxes synthesized exclusively by vascular plants. Records of vascular plant leaf wax d13C, dD, and average carbon chain length from Cariaco Basin sediments agree with previously established local pollen and climate records. Differences in dD between short and long-chain fatty acids suggest a marine source for the former and a terrestrial source for the latter. Leaf wax dD records the hydrogen isotopic composition of environmental water combined with evaporative enrichment within leaf spaces, and as such may act as a proxy for local aridity, whereas d13C is a proxy for “humid” C3 versus “arid” C4 metabolic pathways in plants.
Deglacial data from combined dD and d13C analyses exhibit enrichment during stadials and depletion during interstadial periods, indicating that C3 plants and warm/wet conditions predominated in the Cariaco watershed during Bølling-Allerød and Holocene periods, and C4 plants proliferated during cool/arid Glacial and Younger Dryas intervals. In addition to the information available from isotopes, distributional variations in plant biomarker homologues (average chain length - ACL) also record differences between “arid” and “humid” vegetation sources. An ACL index for fatty acid homologues confirms that tropical vegetation biomass in the Cariaco region shifted rapidly between arid grassland and wet forest during deglaciation, in phase with gray scale and the characteristic trend of climate oscillations in the high-latitude North Atlantic.
Here we present records of terrestrial vegetation and continental aridity throughout the past 1500 years, and during the climatic shifts of the Little Ice Age, a period of drought in the Cariaco watershed. Trace element concentrations (%Ti, %Fe) from Cariaco sediments record diminished runoff and precipitation during the LIA possibly as severe as the earlier Younger Dryas. Extended dry periods of such magnitude suggest a significant impact on the terrestrial environment and local populations. ACL and isotopic measurements on leaf waxes will be used to evaluate the extent of dry conditions and perturbations to the terrestrial environment, and place LIA changes in the context of late Holocene variability.
Deadly deluges and shattered landscapes: El Niño and earthquakes on the Andean Coast
David K. Keefer US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025
Michael E. Moseley Department of Anthropology, University of Florida, Gainesville, FL
Earthquakes and El Niño have always been part of life along the Andean coast. While normal atmospheric conditions create one of earth's driest deserts there, the weather changes dramatically during El Niño, when moisture-laden air sweeping onshore from the tropical eastern Pacific typically brings heavy rainfall and severe flooding to this region. Effects of historical El Niño events have varied considerably in geographic extent and intensity, and the events are variously rated as Weak, Moderate, Strong, or Very Strong.
Because of the close historical correlation between El Niño and flooding along the central Andean coast, prehistoric flood deposits found there have been widely interpreted as evidence of earlier El Niño events. Indeed, calamitous erosion and burial of prehistoric cultural landscapes led to the first geoarchaeological detection of an ancient El Niño in the 1970’s. This prehistoric flood and a number of others are inferred to be the products of “Mega-Niños” because the scale of the associated deposits substantially exceeds that of the most severe twentieth century Andean coastal floods.
Situated adjacent to the subduction zone bounding two major tectonic plates, this Andean coast is also home to some of the world's largest earthquakes. These include the magnitude 9.5 Chilean earthquake of 1960, the largest ever recorded, and the magnitude 8.4 southern Peru event of 2001, the largest worldwide between 1965 and the time of its occurrence. Along the southern Peru segment of this plate boundary alone, great earthquakes have been recorded on average about once a century. Such earthquakes can cause great loss of life and disruption of normal society, as when the magnitude 7.9 Peru earthquake of 1970 killed 66,000 people and devastated a large area of the country.
Such earthquakes can also have profound and lasting effects on the landscape. The 1960 earthquake caused thousands of landslides, including a giant rock avalanche that buried two cities, claimed 25,000 lives, and transported millions of cubic meters of sediment off the mountainside. Much of the landslide material was subsequently transported to the sea during post-earthquake El Niño flooding, thus creating an anomalous situation of increased sediment movement arising from a seismically disturbed landscape. The 2001 earthquake in southern Peru also created a highly disturbed "shattered landscape." Elements of this shattered landscape include abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of tributary channels. Such effects are inferred to prime the landscape for generating increased run-off, erosion, and sediment transport during subsequent El Niños. Interpretations of the paleo-flood record in this region therrefore must consider the potential for seismic shattering of the landscape to combine with El Niño to generate anomalous flooding. In the Osmore region of southern Peru, where we have studied the paleo-flood record, sedimentary sequences that extend through the early Holocene and the late Pleistocene are characterized by a predominance of large-scale deposits, but relatively few deposits approximating those of recent twentieth century floods. Characteristics of those deposits indicate that the combination of seismic shattering with El Niño may account for some but not all of these "Mega-Niño" records.
POSSIBLE SOLAR SIGNALS IN HISTORICAL DROUGHTS IN CENTRAL AND SOUTHEASTERN MEXICO
B. Mendoza1, E. Jáuregui1, V. Velasco1, V. García-Acosta2 and G. Cordero3
(1) UNIVERSIDAD NACIONAL AUTÓNOMA DE MÉXICO, MÉXICO D. F. MÉXICO
(2) CENTRO DE INVESTIGACIONES Y ESTUDIOS SUPERIORES EN ANTROPOLOGÍA SOCIAL, MÉXICO D. F, MÉXICO
(3) UNIVERSIDAD COMPLUTENSE, MADRID ESPAÑA
We use a catalogue containing an unprecedented amount of historical data in Mexico covering almost six centuries (1400-1900). This is a catalogue of agricultural disasters, which includes events associated with hydro meteorological phenomena or hazards whose effects were mainly felt in the agricultural sector, such as droughts.
We perform an analysis of the historical series of droughts in central Mexico for the period 1450-1900. Analyzing the periodicities of the drought time series we found that the most conspicuous ones are the quasi-bidecadal frequencies of 18.9 and 21 years.
Using the same catalogue for the southeastern part of Mexico we carried out an analysis of the historical series of droughts for the period 1502-1899. Studying the periodicities of the drought time series we found that the most prominent frequencies are ~ 70 years and again the quasi-bidecadal one at ~ 20 years.
A further analysis of both drought series using the wavelet technique allows us to identify signals common between droughts and various solar activity phenomena. We discuss the implications of these results in the context of solar activity and climate.
Site climatic sequence congruencies in Yucatan?
Paleoclimatic and archaeological implications
Lewis C. Messenger, Jr. (Skip)
Haden Bowie
Department of Anthropology
Hamline University
Saint Paul, MN 55104
The reconstruction of ancient regional climatic trajectories has often been based upon data derived from various kinds of cores taken from fortuitous locations where conditions were optimal for the preservation of sequentially-laid strata or laminations containing relevant materials allowing for dependable proxy data and hence, climatic, vegetational, and landscape reconstructions. Luckily, we find that we are able to employ an ever-increasing number of analytic strategies for such reconstructions, ranging from the study of glacial ice cores, tree rings (dendroclimatology), pollen and other plant and animal micro- and macro-fossils, and so on. Each one of these approaches depends upon the likelihood of long, uninterrupted sequences of data-containing laminations, but clearly, such a host of approaches cannot often be brought to bear in a single locale. Hence, we are constantly forced to speculate about a regional climatic sequence based on a core or data set derived from one single location within a region.
In the case of the Maya region of peninsular Yucatan, such retrodictions have relied primarily upon the analysis of a relatively small number of cores taken from some of the lakes and cenotes found in this expansive karst landscape (Punta Laguna, Cobá, Chichancanáb, Sayaucil and Chulchaca). While the analysis of such cores is important and praiseworthy, we cannot consider the areas of central and northern Yucatan Peninsula currently saturated with data sets.
As part of the research conducted previously to investigate the detection of possible El Nino event signatures in the Maya region, comparative climatic trajectory analysis of historical series data was done for a small number of meteorological observation stations in Yucatan. While congruencies in the graphs of the data for these locations was expected, instead considerable local variability was indicated.
This paper presents the result of our comparative analyses of historical meteorological series data for a greater number of observation stations in the Maya region. The presence of indicators of micro-regional climatic sequence variability has implications for both paleoclimatologists and archaeologists, both interested in regional climatic and landscape reconstruction; both generating environmental scenarios within which ancient people maintained their livelihoods, at times seemingly in control of, while at other times, at the mercy of the inertia of environmental change. Thus, this paper constitutes somewhat of a "cautionary tale" with messages we believe are important for all of us to be aware of when conducting and evaluating current research.
Deciphering recent climate change in central Mexican lake records
Sarah Metcalfe(1) and Sarah Davies(2)
(1) School of Geography, University of Nottingham, University Park, Nottingham NG7 2RD, UK
(2) Institute of Geography and Earth Sciences, University of Wales Aberystwyth, Llandinam Building, Aberystwyth SY23 3DB, UK
The highlands of central Mexico contain a high proportion of the country’s present day lakes, offering opportunities for climatic reconstructions in a range of systems. The area has, however, also been a focus for human settlement since the time of the earliest occupation of the Americas, as well as being subjected to volcanic and tectonic activity, which continues today. The undoubted complexity of this region makes deciphering a clear climatic signal in lake sediment records a challenge, particularly over the last 1,500 years when human impact has been particularly severe. A number of methodological issues arise including the susceptibility of common palaeoecological proxies (pollen, diatoms) to multiple forcing factors and problems of obtaining reliable chronologies in systems where old carbon is reworked and where fluxes of unsupported 210Pb are low. There are few sources of carbonates in the area, so that other proxies using carbonate microfossils or standard stable isotope methods (especially δ18O as an indicator of changes in P-E in hydrologically closed systems), cannot be applied in most cases. Methodological developments, particularly the application of oxygen isotope analysis of diatom silica (δ18Odiatom), open up new opportunities to isolate climatic change from other system changes. Historical drainage of shallow lake and marshland areas and more recent drawdown of regional groundwater for irrigation, has led to the complete loss of recent sediments in some areas.
Published lake records indicate that the last 1,500 years have been marked by strong climatic variability, superimposed on continuing high levels of anthropogenic impact. Dry conditions, probably the driest of the Holocene, are recorded over the period 1,400 to 900 BP. This clearly corresponds to the global period of rapid climate change (RCC), which has been identified by Mayewski et al. (2004) for the interval 1,200 to 1,000 cal. yr BP (‘cool poles, dry tropics’). It has been suggested that this drying may have led to the abandonment of some sites in the northern, drier, part of the central highlands. The nature and timing of climatic change over the last 1,000 years is not well represented in lake sediment records. There are indications of wetter and then drier conditions, the latter corresponding broadly to the ‘Little Ice Age’ of mid- to high latitudes. There are very few cases where it is possible to relate lake sediment records to the climatic information contained in the abundant historical archives, which mark the Hispanic period (from AD 1521). The developing dendroclimatology for the central highlands will offer another source of palaeoclimatic data against which to test lake records. Interestingly, there is little evidence from central Mexico to support the idea of a ‘cool poles, wet tropics’ RCC starting at about 600 cal. yr BP suggested. A range of mechanisms (e.g. solar cycles, ENSO variability) have been proposed to explain climatic variability over the last 1,500 years, but current lake records from central Mexico are inadequate to test these.
Historical climate variability, climatic hazards, and societal impacts in the Southeast United States
Cary J. Mock Department of Geography, University of South Carolina, Columbia, SC 29208
Dennis B. Blanton Shirley Plantation, 501 Shirley Plantation Road, Charles City, Virginia 23030
The Southeastern United States, encompassing the region east of the Mississippi River and including the region from Virginia southward, possesses some of the longest documentary and early instrumental climatic data for North America, with high-quality English language records dating back to the early eighteenth century. Historical climatic data are particularly dense spatially after 1783, enabling reconstructions of precipitation, temperature, and the length of the growing season. The historical data provide reconstructions of extreme meteorological events, such as floods, hurricanes, and snowstorms. The historical data also provide important information on verifying climatic reconstructions from tree-ring data, examining spatial variations of climate in response to teleconnections such as ENSO (El Nino/Southern Oscillation), and on assessing historical climatic impacts such as Yellow Fever epidemics. The early instrumental data are from the U.S. Army Surgeon General from military forts, observers of the Smithsonian Institution, the Signal Service, and some private observers. Original records of daily data were carefully assessed for discontinuities from examining diurnal temperature ranges and daily precipitation amounts. The temperature data were corrected for different fixed time observations to make their results compatible with the twentieth century records. Copious documentary (non-instrumental) data, covering most of the American South, came mostly from plantation diaries and newspapers.
We present results of our climatic reconstructions of time series of reconstructed temperature, precipitation (particularly rain day counts), growing season lengths, and tropical cyclones from selected locations within Virginia, South Carolina, and southern Louisiana that yield the longest records. We also present some spatial (widespread regional-scale) reconstructions of extreme weather events and societal responses, they include the winter of 1827-28 (which is listed as a major El Nino event), the severe freezes of February 1835 and April 1849, the widespread floods of 1771 and the early-mid 1790s, the extremely cold and snowy winters of 1856-1857, several 19th century Yellow Fever epidemics, and major hurricanes that impacted Charleston SC since the early1700s.
Some results to date include 1) persistent decadal warm-season drought over much of the Southeast during the early-mid 1850s, 2) back-to-back occurrence of extremely severe winters such as the 1771 and 1796 floods are unprecedented when compared closely with the variability of the modern record, 3) a different combination of warm winters and wet summers is evident for each city that link with the outbreak of Yellow Fever epidemics in Portsmouth VA, New Orleans LA, and Charleston SC, and 4) the typical temperature responses of cold (warm) winters to El Nino (La Nina) has not always been consistent through time. Regarding the ENSO responses at the seasonal and intra-annual timescales, some of these results suggest that some El Nino years (e.g., 1827-1828) as suggested from other climatic proxies, may not be true El Niño events. In examining historical societal responses to extreme weather hazards with respect to the last 300 years, we find hints of some lessening to events of “minor climatic stress” (e.g., category 1-2 hurricanes that impacted Charleston SC). However, given the rather infrequent occurrence of some extreme weather events, we also suggest that events involving “major climatic stress”, such as the James River floods of 1771 and the Great Charleston Hurricane of 1752, may impact society at levels much higher in the future than what has been experienced in the last century.
Decadal anomalies of rainfall and temperature in the Yucatan Peninsula for the twentieth century
Roger Orellana, Celene Espadas & José Antonio González-Iturbe
Centro de Investigación Científica de Yucatán. Calle 43 No 130. Col. Chuburna de Hidalgo 97200 Merida, Yuc. Mexico. orellana@cicy.mx
In the Yucatan Peninsula at present there is a rainfall gradient running generally from north to south, which is modulated by the influence of climatic factors, such as its geographic position with respect to the subtropical high-pressure system known as the Bermuda High. As a consequence of this situation the northeast is arid, and the south is very rainy. The peninsula is generally characterized by low topographic relief, and is surrounded by tropical oceanic currents. It is composed of two thermic zones: a warm (mean annual temperature lower than 26OC) and a very warm (mean annual temperature higher than 26OC) region. The transitional zones encompassing the limits of the pluviometric and thermic zones exhibit high variability. Thus, we can suppose that such variations will be evident when we analyze distinct periods.
This work is an analysis of decadal changes in mean annual temperature and rainfall in the Mexican portion of the Yucatan Peninsula. As a source of information we used 110 climatological stations from the states of Campeche, Quintana Roo, and Yucatan. Due to the heterogeneity of the available data it was only possible to do a general comparison of the following decades: 1951-1960, 1961-1970, 1971-1980, 1981-1990, and 1991-2000. Additionally we performed an analysis of long period observatories, such as in Merida, Progreso, Valladolid, Campeche, Ciudad Del Carmen, Champotón, and Chetumal. The results obtained showed the following: 1) Decadal variation in temperature and rainfall is present throughout the analysis period; 2) there is a tendency for increasing temperature throughout the region; 3) negative rainfall anomalies tend to be located southward in the more humid zones. We propose an interpretation of these climatic changes in terms of decadal increase of “hot spots” of temperature (+) and precipitation (-).
Looking for ENSO signals in the past: Natural disasters, impacts and cultural responses in some regions of South America during the XVII, XVIII and XIX centuries
María del Rosario Prieto
Instituto Argentino de Nivología , Glaciología y Ciencias Ambientales (IANIGLA). Adrián Ruiz Leal s/n, Parque San martín, (5500) Mendoza, Argentina
E-Mail: mrprieto@lab.cricyt.edu.ar
Studies made during the last years (Montecinos et al 2000, and others) support the existence of links between the Southern Oscillation (and associated SST anomalies in the Tropical Pacific) and precipitation anomalies in subtropical South America. They have shown that ENSO-related rainfall anomalies occur over regions on both the eastern and western sides of the continent and mainly during the second half of the year. A spatially coherent region has been identified in southeastern South America including southern Brazil, southern Paraguay, Uruguay and eastern Argentina.
The same close connection is found between snow melting, river streamflow and severe El Niño events in the oriental slope of the Argentine-Chilean Central Andes (33°S) in the next summer season following an increased winter snow accumulation in the cordillera there would be a significant streamflow enhancement accompanied by large swellings (Campagnucci and Vargas, 1993). Otherwise, in the Tropical Andes negative rainfall anomalies occur during seven ENSO events above eight according to Ronchail (1998).
To evaluate the occurrence of these phenomena in other historical moments, various proxies are used, such as archival records. The use of archive documentation permits not only to trace the El Niño events through the five last centuries in South America, but also an evaluation of its intensity, taking into account its effects over the vulnerable pre-industrial societies of the past. As it is known that severe and prolonged climatic events of the El Niño type at a regional scale or larger can deeply impact the population of the past centuries. These catastrophic effects can operate through the material damages, but mainly through the lack of food, famine, disease, pests, demographical decline, massive mortality, economic crisis and social and politic conflicts. Even though the strongest signal of the El Niño event is developed on the northern Peruvian coast, the occurrence of natural catastrophes—with their social and economical consequences—that can be related with the ENSO in the South American regions involved in the above-mentioned studies, has been considered. Their results can be used to widen the historical record of the phenomena, to perfection the intensity scale and eventually corroborate or refute the available historical data, thus contributing to the elaboration of a more trustable chronology.
Representative study cases are commented, directly related with the physical and socioeconomic effects produced by the El Niño occurrence in three South American regions: the large floods of the Parana river during the 17th century, their impact and the population responses; the periods of droughts in the Bolivian Altiplano during the second half of the 18th century-first decades of the 19th century ; and finally, the extraordinary floods of the Mendoza River-Argentina as consequence of the exceptional snowfall in the Cordillera de los Andes during the same period.
The following criteria were established to select the cases: i) The existence of prolonged, intense and continued phenomena along time; and ii) Catastrophic effects underwent by the population; iii) Intensity and magnitude of the impact according to the population vulnerability. Generally, the goal has been to verify that the economic and social crisis in the analyzed cases show acceptable connections with the El Niño events, contributing to refine the existing chronologies.
Literature cited
Compagnucci R & W Vargas 1993. Snowfall in the Cordillera de Los Andes and the ENSO Events. Preprint 4th International Conference on Southern Hemisphere Meteorology and Oceanography. 28 March-2 April 1993. Hobart, Australia. eds. AM. Met. Soc. 332-333.
Montecinos A, Diaz A & P Aceituno. 2000. Seasonal Diagnostics and Predictability of Rainfall in Subtropical South America Based on Tropical Pacific SST. Journal of Climate, vol. 13: 746-758.
Ronchail, J. 1998. Variabilité pluviometrique lors des phases extremes de l’oscillation australe du Pacifique en Bolivie (1950-1993). Bulletin IFEA, Lima.
Climate, risk and history: Are the lessons learned?
Roger S. Pulwarty
NOAA/CIRES/Climate Diagnostics Center
Boulder CO 80305
The past and present alterations of environments throughout the Americas reflect complex histories of human settlement and interactions, small and large-scale water and resource diversions, the development and evolution of resource law, and expanding frameworks of resources management from state control and common property arrangements to increasing calls for privatization. Population increases, economic growth (including agriculture), the rise of urban centers over the last century (and more so recently) have resulted in intense pressures being placed on lands, water, ecosystems and institutions Attention to history shows that people and governments have known about most problems for a long time but have not acted on better knowledge of these past changes, i.e., problems have been accumulating for many years not just when they are publicized. As noted by several researchers and practitioners, learning processes can seek to draw lessons from comparative historical accounts of experience from different places. However, the difficulty lies not only in the drawing of lessons but in the socialization of lessons learned by particular individuals and organizations through their own, direct trial and error experience. Given that uncertainties and conflict are unavoidable, it is precisely this type of learning that is needed if long established issues such as ENSO impacts, drought, and decadal scale changes are to provide useful lessons for emerging issues such as climate and global changes. The presentation focuses on these timescales and the evolution of learning about conjunctive (environment and society) risks. Inattention to these changes or engaging in inadequate responses, allows the incremental accumulation of problems to the point of system criticality or collapse.
As a result of changes in funding since the end of the Cold War, there is an increasingly common trend towards justifying scientific research on its societal relevance. The result is an increasingly distributed knowledge production system in which communication and alliances increasingly develop across existing institutional boundaries. Nowhere is this ascendance more visible than in the international set of activities that result in forecasting El Niño events and their impacts at local levels. The still operative approach has been to ensure a continuing dialogue between authoritative decision-makers in each country or region and experts on various aspects of climate risk assessment. Emphases on 'authority' and 'expertise' alone can reduce contending perspectives and lead to unanticipated consequences. Learning from experience involves identifying and describe existing and past actions and policies appraised as successful and pitfalls in others. The most important parts, however, are (a) to understand and disseminate the policies in other localized or specialized decision making processes, and (b) to engage the governance processes (at different scales) that can adaptively create and incorporate new information into existing experiences in non-idealized contexts.
Spatial patterns of decadal drought and wetness regimes over western North America during the past 1200 years
D.W. Stahle1, F.K. Fye1, E.R. Cook2
1Department of Geosciences, Ozark Hall 113
University of Arkansas, Fayetteville, AR 72701
2Doherty Senior Scholar and Director, Tree-Ring Laboratory
Lamont-Doherty Earth Observatory, Palisades, New York 10964
The network of moisture sensitive tree-ring chronologies now available for North America has been used to reconstruct the summer (JJA) Palmer drought severity index (PDSI) for 286 grid points in a 2.5 x 2.5 latitude/longitude scheme extending from southern Mexico across the USA into southern Canada (Cook et al. 2004). These reconstructions have high temporal and spatial fidelity when compared with instrumental PDSI on annual and decadal timescales. The reconstructions indicate that the 20th Century was relatively moist over the West when compared with the past 1200 years, the severe Dust Bowl and 1950’s droughts notwithstanding. Drought frequency, intensity, and area appear to have been particularly elevated over the West during the Medieval era.
This period of Medieval aridity has been hypothetically linked with high solar irradiance, reduced tropical volcanism, and persistent La Niña-like conditions in the eastern equatorial Pacific (Cook et al. 2004). The spatial structure of decadal moisture anomalies over the West may provide some constraint on this hypothesis. The long-range climate influence of the El Niño/Southern Oscillation (ENSO) over western North America during the late 19th and 20th centuries has been strongest in the Texas-Mexican sector of northern Mexico and the southwestern USA, with drought during La Niña events and wetness during El Niño events. Seven of the ten most extreme decadal droughts over the West in the past 1200 years occurred before A.D. 1600, and six of the ten most extreme decadal pluvials occurred after. The epicenter of decadal drought was located in the ENSO teleconnection province over the Southwest during the Medieval era, but less consistently so after. The ten strongest decadal pluvials of the past 1200 years were spatially heterogeneous and did not tend to recur in the ENSO teleconnection region. The notable exception was the early 20th Century pluvial (1907-1916), the most extremely wet decade in 1200 years, and which was concentrated in the drainage basin of the Colorado River. This period of exceptional wetness inflated expectations of surface water supplies in the Southwest, and provides a modern demonstration of the significant environmental and socioeconomic impacts associated with these decadal droughts and pluvials. The 17th Century Pueblo Drought lasted at least six years (1666-1671) over the same region impacted by the 20th Century pluvial, and provides a compelling contrast to the pluvial and a strong analog for the recent multi-year drought that has severely impacted surface water supplies in the Southwest (1999-2004). Socioeconomically, the 17th Century Pueblo Drought caused starvation, death, and the permanent abandonment of five Puebloan villages in New Mexico.
Cook, E.R., C.A. Woodhouse, C.M. Eakin, D.M. Meko, and D.W. Stahle, 2004. Long-term aridity changes in the western United States. Science 306:1015-1018.
The curse of climate: Records of drought and famine in Central Mexico
Matthew D. Therrell
Dept. of Environmental Sciences, University of Virginia, Charlottesville, VA 22904 USA
David W. Stahle
Department of Geosciences, University of Arkansas, Fayetteville, AR 72701 USA
Jose Villanueva-Diaz
Instituto Nacional de Investigaciones Forestales y Agropecurias (INIFAP)
KM 6.5, Margen Derecha Canal Sacramento, Gomez Palacio, Durango 35140, Mexico
Rodolfo Acuna Soto
Departamento Microbiologia, UNAM, Ciudad Universitaria, Mexico
Eladio Cornejo Oviedo
Departamento Forestal, Universidad Autonoma Agraria Antonio Narro
Buenavista, Saltillo, Coahuila 25315, Mexico
Central Mexico is one of the most populous regions on earth and has historically been heavily impacted by climatic events such as drought. Tree-ring and other paleoproxy reconstructions of climate indicate that the area from central Mexico into the southwestern United States has experienced extreme climate fluctuations over the past 500 to 1000 years. There is an extensive body of colonial and even pre-Hispanic historical documentation regarding the impact of climate on agriculture and society in central Mexico, but long, climate sensitive, tree-ring records with which to compare this rich documentary data have previously not been available for this region.
Analyses of new tree-ring chronologies from Mexico indicate that tree growth is strongly influenced by extreme climatic events such as drought, and that several periods of abnormally poor growth apparent in the tree-ring record are coincident with drought-induced crop failures, famine, and attendant social disruption recorded in historical sources from central Mexico.
For example, maize yield in the highlands of central Mexico is strongly correlated with adequate rainfall early in the growing season (April-June), and precipitation during this season is also highly correlated with Douglas-fir latewood width chronologies from Puebla. The tree-ring data explain 60% of the interannual variability of maize yield average for the states of Mexico, Puebla, Tlaxcala, and Veracruz. Seven of the most severe tree-ring reconstructed maize shortages since 1500 are well documented as periods of agricultural crisis in Mexico and often occurred during episodes of intense drought.
Long tree-ring chronologies from Mexico also verify the chronology of drought years identified in Aztec codices during the prehispanic and early colonial periods, including the infamous drought and "Famine of One Rabbit" in 1454. In fact, the Aztecs associated their calendar year "One Rabbit" with famine and catastrophe and tree-ring data from Mexico indicate that drought occurred in 10 of the 13 years immediately preceding all "One Rabbit" years from AD 882-1558.
Climate variability in central Mexico for the last 800 years
Jose Villanueva-Diaz1, D.W. Stahle, M.D. Therrell, J. Cerano-Paredes
1INIFAP CENID RASPA, Km 6.5 Margen Derecha del Canal Sacramento. Gómez Palacio, Durango. 35140. E-mail: Villanueva.jose@inifap.gob.mx
The study of climate variability is of main importance to analyze the recurrence of extreme events and the influence of atmospheric circulatory patterns. Central Mexico is one of the regions where ancient civilizations flourished or disappeared mainly under the influence of extreme climatic events. Currently, overexploitation of aquifers, water pollution, land-use changes, overpopulation and other factors are exacerbating the availability of hydrological resources on this part of the country. The historical interannual and low frequency hydroclimatic variability that influenced socioeconomical activities of ancient and modern civilizations could be analyzed with dendroclimatic studies.
Precipitation reconstructions for central and northern Mexico using tree-ring chronologies indicate the presence of extreme droughts in the 1450 to 1454 period. This documented drought produced shortages of food, famine, epidemics and lack of water in the Valley of Mexico but this drought has also been observed in climatic reconstructions done for the states of Coahuila, Nuevo Leon, and Durango. A well documented drought is the one occurred from 1540s to the 1570s this megadrought extended from central Mexico to southwestern United States. During this drought the native population of central Mexico was drastically reduced due to epidemic outbreaks and famine. The documented hunger year or “año del hambre” (1785 – 1786) is seen as a drastic drop in growth for those years in an earlywood chronology developed from Douglas-fir trees in Cuahutémoc la Fragua, Puebla. Further reconstructed extensive droughts are those reported for the 1810s, 1860s, 1870s, and 1950s. A recent developed chronology over 800 year length for Queretaro, Mexico will be used to analyze the climate variability on this region and its relationship with ENSO and other circulatory patterns.
Climate and Cultural History in the Americas
Centro Ecológico de Akumal
Quintana Roo, México
March 31–April 2, 2005
List of Participants
Dr. Mark Abbott
Geology and Planetary Science
University of Pittsburgh
4107 O'Hara Street
Room 200 SRCC Building
Pittsburgh, PA 15260-3332 USA
Dr. Rodolfo Acuña-Soto
Departamento de Microbiología y Parasitología
Facultad de Medicina
Universidad Nacional Autónoma de México
Mexico City 04510
Dr. Caspar Amman
National Center for Atmospheric Research
Climate and Global Dynamics Division - Paleoclimatology
P.O. Box 3000
Boulder, CO 80307-3000
Dr. Larry Benson
Chief Arid Regions Climate Project
USGS
3215 Marine St, S