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This study presents a multi-proxy reconstruction of tropical cyclone (TC) activity for the past 800 years from Robinson Lake, located on the north Atlantic seaboard of Nova Scotia, Canada. Two sediment cores were extracted from Robinson Lake and were dated by 210Pb and 14C methods, and analyzed for organic matter content, sediment grain size, and a range of elements and elemental ratios determined by XRF core scanning. A distinct sand layer in the most recent sediments is attributed to Hurricane Juan, which struck the coast of Nova Scotia on September 29, 2003. Our study shows that peaks in grain size farther down-core are generally correlated with abrupt increases in Br and Br/Ti. XRF-derived Br measurements are an indicator of marine organic carbon (MOC), and the increases in Br likely reflect incursions of marine water and nutrients into the lake as a result of storm surges. The results show that the period from ~1475 to 1670 CE contains at least 3–4 storm beds, and are interpreted as the most active TC period within the last ~800 years for this region. Our results are consistent with recent research from Salt Pond, Massachusetts (Donnelly et al. 2015), which provides evidence for heightened TC activity during the same period as our study at Robinson Lake. Our study represents one of the highest latitude paleotempestological studies from the North Atlantic basin which will help the testing of hypotheses concerning long-term changes in North Atlantic TC activity under future climate change scenarios.

Paleotempestology, the study of past tropical cyclone activity, has grown considerably over the past two decades, and there is now a relatively dense network of sites across the Western North Atlantic Basin providing records of past tropical cyclone variability. This paper presents a new database of paleotempestological records generated from 61 studies published between 1993 and 2018 for this region. A total of 266 data entries, consisting of the calibrated ages of individual tropical cyclone events and the boundaries of ‘active’ tropical cyclone periods from the present to 8000 cal. yr BP, along with the site names, geographic coordinates, proxy indicator(s) used, materials upon which dating was undertaken, and information about the depositional basin type (e.g. lagoon, mangrove), are included in the database for each site. The database is housed at the National Oceanographic and Atmospheric Association (NOAA) ( https://www.ncdc.noaa.gov/paleo/study/21391 ) and is available for free download. This publicly available database will permit a greater number of researchers to work on questions related to past tropical cyclone dynamics and more easily allow studies of long-term spatial-temporal tropical cyclone relationships to be undertaken.

We present a 2000-year pollen-based reconstruction of total annual precipitation (ANNP) for North America. Application of Local Indices of Spatial Association (LISA) permitted us to distinguish reg...

Paleotempestology, the study of past tropical cyclones (TCs) using geological proxy techniques, is a growing discipline that utilizes data from a broad range of sources. Most paleotempestological studies have been conducted using “established proxies,” such as grain-size analysis, loss-on-ignition, and micropaleontological indicators. More recently, however, researchers have been applying more advanced geochemical analyses, such as X-ray fluorescence core scanning and stable isotopic geochemistry, to generate new paleotempestological records. In this paper we begin by providing a list of paleotempestological studies for the western North Atlantic Basin and illustrate the spatial coverage of these studies. We then review the premises behind both established and new proxies and discuss their strengths and limitations at resolving past hurricane activity. Lastly, we suggest future directions for paleotempestological research based on our review of the literature that we argue will ultimately lead to a better understanding of TC dynamics under future climate change scenarios.

The Berkeley Earth surface temperature (BETP) project provides gridded global temperature anomaly products using an automated geostatistical approach to adjust station data for systematic biases. Despite its widespread usage, the BETP data set has not been evaluated at the national-scale, especially in data-sparse high latitude environments. This study provides an evaluation of the BETP product across all of Canada using 333 climate stations made available from the homogenized Environment Canada station network (HTcan). Comparison between co-located monthly air temperature anomalies for the two data sets suggests small differences between the two products for mean surface (∼2 m) air temperature. However, the relatively minimal bias in mean temperature is a consequence of contrasting cold and warm biases in minimum and maximum air temperatures, respectively, that are larger but effectively even out when averaged together. The BETP product is shown to exhibit systematic underestimation of recent regional warming in northern Canada which when combined with an overestimation of warmth earlier in the record results in an observable reduction in warming rates for minimum and mean temperature anomalies since 1950. The temporal evolution and spatial pattern of the observed biases suggest that the BETP-automated adjustments to station data in northern Canada miss some inhomogeneities in the raw station data. These results highlight the need for enhanced data recovery and homogenization efforts in data-sparse high latitude regions and emphasize the importance of national-scale climate data sets for evaluating global gridded products. We also recommend caution when using the BETP minimum and maximum monthly air temperature products for long-term trend analyses.

The study of paleofloods provides important information on past flood frequency and intensity for regions where there is a paucity of records; it therefore extends our knowledge of flood occurrence beyond the historical record. Many paleoflood reconstructions come from the arid dry climate of southwestern USA and from Europe, with few studies being conducted in temperate climates of North America. This study uses sediment cores from oxbow lakes to reconstruct past flood events in a temperate region. Cores extracted from two oxbow lakes along the Désert River in southwestern Quebec, Canada, were analyzed for magnetic susceptibility, loss on ignition, and grain size and were radiocarbon dated (14C). Using a combination of magnetic susceptibility variations, along with changes in grain size and organic material content, five floods were identified within the 220 cm core (1300 years) from the North oxbow lake, and six floods in the 118 cm core (600 years) from the South oxbow lake. This study provides evidence to support the use of oxbow lakes in temperate regions as a proxy of past floods, thus helping us understand hydroclimatic changes at regional scales. Data that span a longer period of time and in different environments are key to increase flood modelling accuracy to improve mitigation strategies under a changing climate.

Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between AD 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period AD 1971?2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years. Fil: Ahmed, Moinuddin. Federal Urdu University of Arts, Science and Technology. Department of Botany; Pakistán Fil: Anchukaitis, Kevin J.. Columbia University. Lamont Doherty Earth Observatory; Estados Unidos. Woods Hole Oceanographic Institution; Estados Unidos Fil: Asrat, Asfawossen . Addis Ababa University. School of Earth Sciences; Etiopía Fil: Borgaonkar, Hemant P.. Indian Institute of Tropical Meteorology; India Fil: Braida, Martina . University of Trieste. Dipartimento di Matematica e Geoscienze; Italia Fil: Buckley, Brendan M. . Columbia University. Lamont Doherty Earth Observatory; Estados Unidos Fil: Ulf Büntgen. Swiss Federal Research Institute WSL; Suiza Fil: Chase, Brian M.. Université Montpellier. Département Paléoenvironnements et Paléoclimats (PAL); Francia. University of Bergen. Department of Archaeology, History, Cultural Studies and Religion; Noruega Fil: Christie, Duncan A. . Universidad Austral de Chile. Laboratorio de Dendrocronología y Cambio Global; Chile. Universidad de Chile. Center for Climate and Resilience Research; Chile Fil: Cook, Edward R.. Columbia University. Lamont Doherty Earth Observatory; Argentina Fil: Curran, Mark A. J.. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Diaz, Henry F. . National Oceanic and Atmospheric Administration. Cooperative Institute for Research in Environmental Sciences, ; Estados Unidos Fil: Esper, Jan. Johannes Gutenberg University. Department of Geography,; Alemania Fil: Fan, Ze-Xin . Chinese Academy of Sciences. Xishuangbanna Tropical Botanical Garden ; China Fil: Gaire, Narayan P. . Nepal Academy of Science and Technology. Faculty of Science,; Nepal Fil: Ge, Quansheng. Chinese Academy of Sciences. Institute of Geographical Sciences and Natural Resources Research, ; China Fil: Gergis, Joëlle. University of Melbourne. School of Earth Sciences; Australia Fil: González-Rouco, J Fidel. Universidad Complutense de Madrid. Departamento Astrofísica y CC de la Atmósfera; España Fil: Goosse, Hugues. Université Catholique de Louvain. LemaitreCenter for Earth and Climate Research, Earth and Life Institute; Bélgica Fil: Grab, Stefan W. . University of the Witwatersrand. School of Geography,Archaeology and Environmental Studies; Sudáfrica Fil: Graham, Nicholas. Hydrologic Research Center; Estados Unidos Fil: Graham, Rochelle . Hydrologic Research Center; Estados Unidos Fil: Grosjean, Martin . University of Bern. Oeschger Centre for Climate Change Research & Institute of Geography; Suiza Fil: Hanhijärvi, Sami T.. University of Helsinki. Department of Environmental Sciences; Finlandia Fil: Kaufman, Darrell S.. Northern Arizona University. School of Earth Sciences and Environmental Sustainability; Estados Unidos Fil: Kiefer, Thorsten . International Project Office, Past Global Changes (PAGES); Suiza Fil: Kimura, Katsuhiko. Fukushima University. Department of Symbiotic System Science; Japón Fil: Korhola, Atte A.. University of Helsinki. Department of Environmental Sciences; Finlandia Fil: Krusic, Paul J.. Stockholm University. Department of Physical Geography and Quaternary Geology; Suecia Fil: Lara, Antonio. Universidad Austral de Chile. Laboratorio de Dendrocronología y Cambio Global; Chile. Universidad de Chile. Center for Climate and Resilience Research; Chile Fil: Lézine, Anne-Marie. Université Pierre et Marie Curie. Laboratoire d’Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN); Francia Fil: Ljungqvist, Fredrik C.. Stockholm University. Department of History, ; Suecia Fil: Lorrey, Andrew M.. National Institute of Water and Atmospheric Research Ltd., National Climate Centre Auckland; Nueva Zelanda Fil: Luterbacher, Jürg. Justus Liebig University. Department of Geography, Climatology, Climate Dynamics and Climate Change; Alemania Fil: Masson-Delmotte, Valérie . Laboratoire des Science du Climat et de l’Environnement, Gif-sur-Yvette; Francia Fil: McCarroll, Danny. Swansea University. Department of Geography; Reino Unido Fil: McConnell, Joseph R.. Nevada System of Higher Education. Desert Research Institute; Estados Unidos Fil: McKay, Nicholas P.. Northern Arizona University. School of Earth Sciences and Environmental Sustainability; Estados Unidos Fil: Morales, Mariano Santos. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Moy, Andrew D.. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Mulvaney, Robert. British Antarctic Survey; Reino Unido Fil: Mundo, Ignacio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Nakatsuka, Takeshi. Nagoya University. Department of Earth and Environmental Sciences; Japón Fil: Nash, David J.. University of the Witwatersrand. School of Geography,Archaeology and Environmental Studies; Sudáfrica. University of Brighton. School of Environment and Technology; Reino Unido Fil: Neukom, Raphael . Swiss Federal Research Institute WSL; Suiza Fil: Nicholson, Sharon E.. Florida State University. Department of Earth, Ocean and Atmospheric Sciences, ; Estados Unidos Fil: Oerter, Hans. Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association. Department of Glaciology; Alemania Fil: Palmer, Jonathan G.. University of Exeter. College of Life and Environmental Sciences; Reino Unido. University of New South Wales. Climate Change Research Centre; Australia Fil: Phipps, Steven J.. University of New South Wales. Climate Change Research Centre; Australia. University of New South Wales. ARC Centre of Excellence for Climate System Science; Australia Fil: Prieto, Maria del Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Rivera, Andres. Centro de Estudios Cientificos; Chile Fil: Sano, Masaki. Nagoya University. Department of Earth and Environmental Sciences; Japón Fil: Severi, Mirko. University of Florence. Department of Chemistry ‘Ugo Schiff’; Italia Fil: Shanahan, Timothy M.. University of Texas at Austin. Jackson School of Geosciences; Estados Unidos Fil: Shao, Xuemei. Chinese Academy of Sciences. Institute of Geographical Sciences and Natural Resources Research; China Fil: Shi, Feng. Chinese Academy of Sciences. LASG, Institute of Atmospheric Physics, ; China Fil: Sigl, Michael . Nevada System of Higher Education. Desert Research Institute,; Estados Unidos Fil: Smerdon, Jason E.. Columbia University. Lamont Doherty Earth Observatory; Estados Unidos Fil: Solomina, Olga N. . Russian Academy of Sciences. Institute of Geography; Rusia Fil: Steig, Eric J.. University of Washington. Department of Earth and Space Sciences; Estados Unidos Fil: Stenni, Barbara. University of Trieste. Dipartimento di Matematica e Geoscienze; Italia Fil: Thamban, Meloth. National Centre for Antarctic and Ocean Research; India Fil: Trouet, Valerie. University of Arizona. Laboratory of Tree-Ring Research; Estados Unidos Fil: Turney, Chris S.M.. University of New South Wales. Climate Change Research Centre; Australia Fil: Umer, Mohammed. Addis Ababa University. School of Earth Sciences; Etiopía Fil: van Ommen, Tas. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Verschuren, Dirk. Ghent University. Department of Biology; Bélgica Fil: Viau, Andre E.. University of Ottawa. Department of Geography; Canadá Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Vinther, Bo M.. University of Copenhagen. Niels Bohr Institute; Dinamarca Fil: von Gunten, Lucien . Past Global Changes (PAGES). International Project Office, ; Suiza Fil: Wagner, Sebastian. Helmholtz-Zentrum Geesthacht. Institute for Coastal Research; Alemania Fil: Wahl, Eugene R.. National Oceanic and Atmospheric Administration. National Climatic Data Center; Estados Unidos Fil: Wanner, Heinz. University of Bern. Oeschger Centre for Climate Change Research & Institute of Geography; Suiza Fil: Werner, Johannes P.. Justus Liebig University. Department of Geography, Climatology, Climate Dynamics and Climate Change; Alemania Fil: White, James W.C.. University of Colorado. Institute of Arctic and Alpine Research; Estados Unidos Fil: Yasue, Koh. Shinshu University. Department of Forest Science; Japón Fil: Zorita, Eduardo. Helmholtz-Zentrum Geesthacht. Institute for Coastal Research; Alemania

The use of different modern climate data sets is shown to impact a continental-scale pollen-based reconstruction of mean July temperature (TJUL) over the last 2000 years for North America. Data from climate stations, physically modeled from climate stations and reanalysis products are used to calibrate the reconstructions. Results show that the use of reanalysis products produces warmer and/or smoother reconstructions as compared to the use of station based data sets. The reconstructions during the period of 1050–1550 CE are shown to be more variable because of a high latitude cold-bias in the modern TJUL data. The ultra-high resolution WorldClim gridded data may only useful if the modern pollen sites have at least the same spatial precision as the gridded dataset. Hence we justify the use of the lapse-rate corrected University of East Anglia Climate Research Unit (CRU) based Whitmore modern climate data set for North American pollen-based climate reconstructions.

Le Groupe Intergouvernemental d'experts sur l'Evolution du Climat prevoit que le changement climatique se manifestera par une augmentation de la temperature moyenne mondiale de 2 °C au courant du 21e siecle. Une consequence du rechauffement prevoit un accroissement dans l'intensite et la frequence des extremes meteorologiques dans la region sud-ouest du Quebec, au Canada. Une evaluation des vulnerabilites aux changements climatiques de Mont-Laurier et de Ferme-Neuve a ete entreprise a l'ete 2011. Un total de 25 entrevues et un groupe de discussion ont ete conduits aupres des deux populations, ce qui a permis de mettre en relation les experiences et les connaissances locales avec les projections climatiques et socio-economiques. L'etude souligne l'importance de la diversification des activites economiques et de la population dans la relation entre le climat et le milieu local. Une composition demographique et une economie non diversifiees exposent les deux municipalites aux aleas du climat. Un changement dans la dynamique entre le contexte socio-economique et biophysique tend a exposer davantage Ferme-Neuve aux impacts potentiels du changement climatique. Cependant, une etude plus approfondie de la capacite d'adaptation doit etre conduite aupres des deux communautes afin d'evaluer leurs vulnerabilites respectives The Intergovernmental Panel on Climate Change projects that climate change will increase the global average temperature by 2 °C during the 21st century. Regionally, one consequence is that this increase in temperature is expected to raise the intensity and frequency of extreme weather events in southwestern Quebec, Canada. A vulnerability assessment for climate change in the communities of Mont-Laurier and Ferme-Neuve was conducted during the summer of 2011. A total of 25 interviews and a focus group were conducted within these two communities, in order to relate past experiences and local knowledge with climate and socio-economic projections. This case study shows that the diversification of a population and its socio-economic activities is central to the effect of climate in local communities. Ferme-Neuve could have a greater exposure to the potential impacts of climate variability than Mont-Laurier, due to changes in the dynamics between the socio-economic and biophysical contexts. However, a more extensive study on the adaptive capacity of both communities must be conducted in order to assess their vulnerabilities.

Evaluation of Labrador air temperatures over the past century (1881–2011) shows multi-scale climate variability and strong linkages with ocean-atmospheric modes of variability and external forcings. The Arctic Oscillation, Atlantic Multidecadal Oscillation, and El Nino Southern Oscillation are shown to be the dominant seasonal and interannual drivers of regional air temperature variability for most of the past century. Several global climate models show disagreement with observations on the rate of recent warming which suggests that models are currently unable to reproduce regional climate variability in Labrador air temperature. Using a combination of empirical statistical modeling and global climate models, we show that 33 % of the variability in annual Labrador air temperatures over the period 1881–2011 can be explained by natural factors alone; however, the inclusion of anthropogenic forcing increases the explained variance to 65 %. Rapid warming over the past 17 years is shown to be linked to both natural and anthropogenic factors with several anomalously warm years being primarily linked to recent anomalies in the Arctic Oscillation and North Atlantic sea surface temperatures. Evidence is also presented that both empirical statistical models and global climate models underestimate the regional air temperature response to ocean salinity anomalies and volcanic eruptions. These results provide important insight into the predictability of future regional climate impacts for the Labrador region.

The temperature of the warmest month was reconstructed for the past 2000 years using 748 pollen sites from the North American Pollen Database. The Modern Analog Technique was used to quantify paleoclimate conditions using a modern pollen database with calibration sites from across North America. Across North America, both the Medieval Warm Period (MWP) and Little Ice Age (LIA) were cooler than the present (AD 1961–1990). The MWP was warmer than the LIA over at least the boreal and eastern portions of the continent and perhaps across the continent. These reconstructed anomalies during the MWP and LIA are significant anomalies from the long-term neoglacial cooling. The atmospheric circulation was likely dominated by a poleward shift of the summer Subtropical High Pressure system in the North Atlantic during the MWP.

Databases of accumulated paleoecological and archaeological records provide a means for large-scale syntheses of environmental and cultural histories. We describe the current status of the Canadian Archaeological Radiocarbon Database (CARD), a searchable collection of more than 36,000 14C dates from archaeological and paleontological sites from across North America. CARD, built by the late Dr Richard Morlan of the Canadian Museum of Civilization, consists of uncalibrated 14C data as well as information about the material dated, the cultural association of the date (e.g. Paleoindian, Archaic, Woodland), and its geographic location. The database can be used to study questions relating to prehistoric demography, migrations, human vulnerability to environmental change, and human impact on the landscape, but biases relating to sampling intensity and taphonomy must first be accounted for. Currently, Canada and the northern United States are well represented in the database, while the southern United States is underrepresented. The frequency of 14C dates associated with archaeological sites increases through time from 15,000 cal yr BP until European contact, which likely reflects, among other factors, both the destruction of older cultural carbon due to erosion and dissolution and increasing population numbers through time. An exploratory analysis of the dates reveals their distribution in both time and space, and suggests that the database is sufficiently complete to enable quantitative analysis of general demographic trends.

Large radiocarbon datasets are increasingly used as a paleodemographic proxy, although potential sources of bias in such records are poorly understood. In this paper, we use more than 25,000 radiocarbon dates extracted from the Canadian Archaeological Radiocarbon Database (CARD) to estimate long-term population trends in North America, while critically examining biases in such records. The frequency distribution of CARD dates shows a positive curvilinear pattern, such that older dates exist in lower numbers than more recent dates, which in part reflects the removal of cultural carbon from the archaeological record through processes such as erosion and dissolution. The average annual growth rate of radiocarbon dates in CARD was calculated and used to derive estimates of the population of North America from the Paleo-Indian to the Contact Periods. While taphonomic bias has likely affected the CARD data, other factors, such as the overrepresentation of Paleo-Indian and Archaic radiocarbon dates, may have offset any bias due to taphonomy. A quantitative reconstruction of Native American population shows that population increased rapidly around 2000 cal yr BP, reaching a maximum of 2,500,000 people by ∼AD 1150. From this time until European contact, the population declined, possibly due to the effects of increased sedentism and population density.

Regional paleoclimate reconstructions for northern Canada quantify Holocene climate variability on orbital and millennial time scales and provide a context to better understand the current global warming. The reconstructions are based on available pollen diagrams from the boreal and low Arctic zones of Canada and use the modern analog technique (MAT). Four regional reconstructions document the space–time evolution of the climate during the Holocene. Highest summer and winter temperatures anomalies are found in central Canada during the early Holocene. Eastern Canada was relatively cool in the early Holocene, whereas central Canada was warmest at that time. Labrador was relatively dry in the early to mid-Holocene during which time western Canada was relatively moist. Millennial-scale temperature variations, especially the Medieval Warm Period and Little Ice Age are seen across the continent, with some suggestion of time-transgressive changes from west to east. At the millennial scale, precipitation anomalies are of opposite signs in eastern and western Canada. The results herein indicate that modern increases in temperatures in northern Canada far exceed natural millennial-scale climate variability.

We present new temperature and precipitation reconstructions for the past 25 000 cal. years BP from across eastern Beringia based on a network of pollen diagrams, an updated modern pollen calibration database, and an improved methodology using the modern analogue technique (MAT). Time series show July temperatures were around 4 °C lower during full glacial and January temperatures were about 2 °C lower than present. Annual temperatures rose beginning around 16 000 cal. years BP, reaching a maximum around 12 000 cal. year BP. The warming was more rapid in southern Beringia. Annual precipitation varied by 250 mm during the past 25 000 cal. years BP. Maps of reconstructed precipitation patterns show increasingly drier conditions since 12 000 cal. years BP. that vary regionally, suggesting Holocene atmospheric circulation changes at multiple time and space scales. Orbitally forced seasonality changes during the late glacial and early Holocene resulted in reversed seasonal temperature reconstructions due to methodological constraints using the MAT and (or) non-analogue conditions. The magnitude of millennial-scale climate variability in this region was greater during the last glacial and late glacial periods than during the past 8000 years.

Aim Using a new approach to analyse fossil pollen data, we investigate temporal and spatial patterns in Populus (poplar, cottonwood, aspen) from the Late Glacial to the present at regional to continental scales. Location North America. Methods We extracted data on the timing and magnitude of the maximum value of Populus pollen from each pollen diagram in the North American Pollen Database (NAPD). The information was plotted in histograms of 150-year bins to identify times when Populus was abundant on the landscape. We also mapped the maximum values to identify spatial patterns and their causes. Results Our analyses show that there have been several periods since the Late Glacial when Populus was abundant on the landscape: (1) from 12.35 to 12.65 kyr bp, in eastern North America, largely in response to the opening of the forest following the onset of the Younger Dryas; (2) from 10.85 to 11.75 kyr bp, following the termination of the Younger Dryas; and (3) during the last 150 years, as land was cleared for agricultural use, especially in the midwestern United States. Main conclusion Since the Late Glacial, changes in the abundance of Populus were caused more by the effects of abrupt climate change on its major competitors, rather than the direct effects of climate on Populus itself.

RESUMEN (Ingles) La linea de investigacion sobre los procesos de ensenanza y aprendizaje cientifico basada en modelos analogicos ha adquirido relevancia, pero notamos que son pocas las aplicaciones en el aula, sobre todo en el nivel medio de ensenanza. Los modelos didacticos analogicos son una herramienta importante para la instruccion pero a condicion de que el profesor y los alumnos adquieran una vision en comun sobre el analogo y se describan sus limitaciones comparado con el modelo teoretico. Se espera del alumno una toma de conciencia sobre sus procesos y eventos cognitivos para que pueda evaluar los progresos y resultados, comprendiendo su propia version acerca de la naturaleza de su conocimiento y sobre el proceso de aprendizaje, es decir sobre sus esencias epistemologicas. En este trabajo se evalua la eficiencia de un modelo didactico analogico para la ensenanza de los conceptos de masa, peso y gravedad mediante un estudio correlacional, cuasiexperimental con posprueba y grupo control. Palabras claves: aprendizaje activo; estrategias de ensenanza; masa, peso y gravedad. Modelos analogicos.

Interpreting the postglacial climate history of the European continent using pollen data has proven difficult due in part to human modification of the landscape. Separating climate from human-caused changes in the vegetation requires a strategy for determining times of change across the entire region. We quantified transitions in the vegetation across Europe during the past 12,000 years using a mixture model approach on two datasets: radiocarbon dates from pollen diagrams and zone boundaries from selected reference sites. Major transitions in the vegetation, as recorded in pollen diagrams, appear synchronous across the continent. These transitions were also synchronous with those identified in North America pollen diagrams and major environmental changes recorded in North Atlantic marine records and Greenland ice cores. This synchronicity suggests that the major vegetation transitions in Europe during the Holocene and late glacial were primarily caused by large-scale atmospheric circulation change. These climate changes may have caused some of the cultural, political and migration changes in European societies during the Holocene.

Summary 1Species-level pollen identifications within the genera Acer, Fraxinus and Juglans have the potential to increase the detail available from regional- and landscape-scale studies of palaeo-forest dynamics. 2Data from the North American Pollen Database (NAPD) and the North American Modern Pollen Database (NAMPD) for sites in eastern North America for which species-level identifications have been recorded enabled us to consider pollen taxonomy at high resolution. 3Species within each of Acer, Fraxinus and Juglans have important differences in habitat, functional type and responses to climatic change. Analysis of the modern distribution of these taxa and their pollen rains confirms that species-level pollen identifications provide detailed ecological information, but the lack of distinction to the species level in many fossil and modern pollen studies renders palaeoenvironmental reconstructions incomplete. 4Within each of three selected high-resolution sites, ordinations indicate that individual species of Acer, Fraxinus and Juglans follow different trajectories through the Holocene, showing that analysing only generic categories results in the loss of ecologically valuable information. For example, pollen of Acer rubrum increased in abundance in response to canopy openings in a southern Ontario forest around 500 years ago, while that of A. saccharum declined. Similarly, Juglans nigra pollen percentages increased while J. cinerea decreased at this time. 5Regional-scale comparisons of pollen percentage curves indicate that, despite the uncertainties associated with the low temporal resolution and the chronologies, it is reasonable to conclude that individual species of Acer, Fraxinus and Juglans responded synchronously to palaeoclimatic changes within each region. 6Taking analyses to the specific level shows that different species followed different tracks in their post-glacial history, a fact previously blurred by less resolved taxonomy. This information is meaningful in biogeographical terms, providing much more specific evidence of how the selected trees behaved in the past.

The modern pollen network in North America and Greenland is presented as a database for use in quantitative calibration studies and paleoenvironmental reconstructions. The georeferenced database includes 4634 samples from all regions of the continent and 134 pollen taxa that range from ubiquitous to regionally diagnostic taxa. Climate data and vegetation characteristics were assigned to every site. Automated and manual procedures were used to verify the accuracy of geographic coordinates and identify duplicate records among datasets, incomplete pollen sums, and other potential errors. Data are currently available for almost all of North America, with variable density. Pollen taxonomic diversity, as measured by the Shannon–Weiner coefficient, varies as a function of location, as some vegetation regions are dominated by one or two major pollen producers, while other regions have a more even composition of pollen taxa. Squared-chord distances computed between samples show that most modern pollen samples find analogues within their own vegetation zone. Both temperature and precipitation inferred from best analogues are highly correlated with observed values but temperature exhibits the strongest relation. Maps of the contemporary distribution of several pollen types in relation to the range of the plant taxon illustrate the correspondence between plant and pollen ranges. r 2005 Elsevier Ltd. All rights reserved.

Aim To document the post-glacial migration of the major aquatic macrophytes of North America. Location North America north of Mexico. Methods Aquatic macrophyte pollen were extracted from the North American Pollen Database. The modern pollen distribution was mapped and related to the climate to document the geographical and climatic constraints on these taxa. The fossil pollen were mapped at 2-ka intervals for the past 21 ka. Results Numerous genera were present in ice-free Alaska during the Last Glacial Maximum, and south of the Laurentide Ice Sheet in the southeast. Those taxa with the widest modern climatic ranges migrated rapidly into ice-marginal areas, first in the west and then in the east of North America. Subsequent changes in the range and abundance were smaller. Main conclusions There were four migration routes of aquatic macrophytes during the late-glacial and post-glacial periods: a southward migration from Alaska between 14–13 and ka, a northern migration in the west at the same time into the ice-free Cordilleran region, and movements east and west of Appalachia as early as 19 ka for some taxa into the lower Mississippi and into the upper Mississippi and Great Lakes by 11 ka. As the Laurentide ice sheet wasted, aquatic taxa with the broadest contemporary temperature tolerances rapidly occupied ice-marginal environments.

This chapter presents some narratives of LGBTQ men and women attending Catholic universities in the greater Chicago area. These individuals recount in their own words what it has been like to learn about Catholic teachings on homosexuality, or to be bullied by both teachers and students, or to encounter silencing among family members and peers, or, most poignantly, to experience the suicide of a friend and lover. It captures these young people’s descriptions of their experiences and the ways in which many of them have employed resources from the Christian and Catholic traditions to empower themselves and others. The chapter situates these intensely personal testimonies against the background of Catholic social ethics, laying the groundwork for further practical-theological explorations of their narratives.

Lake level fluctuations provide evidence about past variations in the global hydrological balance. The geostatistical approach is here used to more objectively identify global patterns using an ensemble of lake level databases by examining spatial autocorrelation between sites. The spatial structures of the lake level data are then modeled and grids produced for the last 12,000 years at 3000-year intervals using ordinary and indicator kriging techniques. The two gridding techniques produced almost identical estimated regional lake status patterns, thus suggesting a robust estimation. The resulting lake-status grids are in general agreement with previous paleoclimatic reconstructions using only site-by-site lake status point maps; however, the reduction of local fine-scale variability resulted in more coherent regional spatial patterns in areas of high local variability. The 6 ka lake-status grids were compared to simulations of four atmospheric general circulation models to illustrate their usefulness in validating broad-scale climate model outputs.

The distribution and abundance of Sphagnum spores in North America and Eurasia are mapped for the past 21 ka. The present-day distribution of abundant Sphagnum spores corresponds closely to areas with peatland development, with maximum Sphagnum abundance between 630 and 1300 mm annual precipitation and between −2° and 6°C mean annual air temperature. During the Wisconsin glaciation, there were apparently not large areas of peatland in North America, except in Alaska. High Sphagnum spore percentages were found in eastern North America during deglaciation. Major peatland development occurred in boreal North America after 9 ka and there was a southward movement of high Sphagnum spore abundance after 5 ka in the western Great Lakes region. Major peatland development began after 9 ka in Europe and Asia. On the basis of maps of the area supporting peatlands, carbon accumulation in peatlands is estimated to be low prior to 11 ka, increased slightly between 11 and 5 ka, and greatly increased during the past 5 ka.

Abrupt Climate C Geophysical Mon Copyright 2011 b 10.1029/2010GM Databases of ecological and cultural records, especially of pollen diagrams, record climate variability of several time scales during the Holocene and late glacial. Results from lake and wetland ecosystems geographically extend the evidence of rapid climate change obtained from ice cores and ocean sediments. Continental and regional climate curves for North America, based on pollen diagrams from the North American Pollen Database, illustrate abrupt changes on the order of every ~1000 years during the past 12 kyr, and major times of change in North American pollen records are coherent with vegetation changes across Europe. Novel analyses of the database show that even taxa that are widespread and with presumably broad climate tolerances were affected by abrupt climate changes such as the Younger Dryas and illustrate the complexity of ecosystem response to these changes. Reconstructions of freshwater as well as terrestrial ecosystems across northern Canada also show how climate variability affects terrestrial and freshwater ecosystem-level properties such as nutrient cycling. These results can be used to reconstruct the spatial patterns of abrupt climate change, as well as the impacts of climate change on ecosystem and cultures.

Se presenta el proceso de construcción de una propuesta pedagógica para la enseñanza de conceptos básicos de termodinámica basada en la utilización de relatos literarios. En este contexto y siguiendo los lineamientos didácticos sugeridos por algunos autores se presenta el diseño de una actividad que utiliza el cuento "El Demonio de Mawell" de Gamow, para ser implementada en clases de la Asignatura Química General I de la Facultad de Ingeniería de la Universidad Nacional de Mar del Plata en Argentina. Esta modificación en el enfoque de la enseñanza muestra como las narraciones que involucran contenidos científicos pueden ser empleadas por los docentes de ciencia como estrategia para aumentar el interés y motivación de los estudiantes. El cuento seleccionado, permite abordar conceptos termodinámicos a través de un modelo microscópico, que conduce a que los alumnos alcancen un mayor grado de racionalismo en su perfil epistemológico.

[1] A mean continental July temperature reconstruction based on pollen records from across North America quantifies temperature variations of several timescales for the past 14,000 cal yr BP. In North America, temperatures increased nearly 4� C during the late glacial, reaching maximum values between 6000 and 3000 cal yr BP, after which mean July temperatures decreased. Superimposed on this orbital-scale trend are millennial-scale temperature variations that appear coherent in structure and frequency with highresolution ice, marine and other terrestrial paleoclimate records of the Holocene. During the Holocene, climate in North America appears to have varied periodically every � 1100 years rather than the � 1500 year cycle found during the last glacial period. Coherence at frequencies between 900 and 1100 years between land, ice, and ocean records suggests a common forcing associated with widespread surface impacts during the Holocene. These results provide important insight to the global warming debate, as the observed twentieth century temperature increase appears unprecedented compared to our mean North American temperature reconstruction of the past 14,000 years.

he PAGES 2k Network has formed to study climate change over the last two millennia at a regional scale, based on the most com- prehensive dataset of paleoclimate proxy-re- cords possible. In 2011, at its second network meeting in Bern, Switzerland (von Gunten et al. 2012) the network formally acknowledged that the envisioned data-intensive multi- proxy and multi-region study must be built on the foundations of efficient and coordinat - ed data management. In addition, the group committed to PAGES general objective to pro- mote open access to scientific data and called for all records used for, or emerging from the 2k project to be publicly archived upon publi- cation of the related 2k studies. Architects of the home for 2k data The National Climatic Data Center at the National Oceanic and Atmospheric Administration (NOAA) offered to host the primary 2k data archive. They set up a dedi- cated NOAA task force to tailor the 2k data archive to the specific needs of the 2k project and to coordinate archiving with NOAA's data architecture and search capabilities. The 2k groups nominated regional data managers to provide input from the users' end. Over the last two years, the regional 2k data managers have worked closely with NOAA to tailor the database infrastructure and prepare the upload of the 2k data. In addi- tion, they provided expertise to help promote improvements in NOAA's archival of paleosci- entific data in general. Since the data manag - ers of the regional 2k groups are spread across the globe, the collaboration was organized around bi-monthly teleconference meetings under the lead of NOAA. In spite of the occa- sional unearthly meeting hours for some, the interaction between the 2k data and NOAA database groups has worked fruitfully, as the following achievements show.

We present two reconstructions of annual average temperature over temperate North America: a tree-ring based reconstruction at decadal resolution (1200–1980 CE) and a pollen-based reconstruction at 30 year resolution that extends back to 480 CE. We maximized reconstruction length by using long but low-resolution pollen records and applied a three-tier calibration scheme for this purpose. The tree-ring-based reconstruction was calibrated against instrumental annual average temperatures on annual and decadal scale, it was then reduced to a lower resolution, and was used as a calibration target for the pollen-based reconstruction. Before the late-19th to the early-21st century, there are three prominent low-frequency periods in our extended reconstruction starting at 480 CE, notably the Dark Ages cool period (about 500–700 CE) and Little Ice Age (about 1200–1900 CE), and the warmer medieval climate anomaly (MCA; about 750–1100 CE). The 9th and the 11th century are the warmest centuries and they constitute the core of the MCA in our reconstruction, a period characterized by centennial-scale aridity in the North American West. These two warm peaks are slightly warmer than the baseline period (1904–1980), but nevertheless much cooler than temperate North American temperatures during the early-21st century.

This article offers a reflection upon the process of intercultural collaboration in light of a global feminist theology immersion pedagogy project, which brought together young scholars from Kenya and the United States. The authors use dualistic categories arising in feminist theological discourse to discuss the ways in which they negotiated difference in the context of intercultural research and collaborative learning. Obioma Nnaemeka’s nego-feminist stance, a feminism of negotiation, provides a way forward for intercultural feminist collaboration as it corresponds to the cultural, practical, and methodological insights of the immersion experience.

There is debate concerning the spatial extent and magnitude of the recently identified 1500 yr climate oscillation. Existing evidence is largely restricted to the North Atlantic and adjacent landmasses. The spatial extent, magnitude, and effects of these climate variations within the terrestrial environment during the Holocene have not been established. We show that millennial-scale climate variability caused changes in vegetation communities across all of North America with a periodicity of 1650 ± 500 yr during the past 14 000 calendar years (cal yr). Times of major transitions identified in pollen records occurred at 600, 1650, 2850, 4030, 6700, 8100, 10 190, 12 900, and 13 800 cal yr B.P., consistent with ice and marine records. We suggest that North Atlantic millennial-scale climate variability is associated with rearrangements of the atmospheric circulation with far-reaching influences on the climate.