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Articles 1 - 30 of 79
Full-Text Articles in Physical Sciences and Mathematics
Elevation-Dependent Warming In Mountain Regions Of The World, Mountain Research Institute, Nicolas Pepin, Raymond S. Bradley
Elevation-Dependent Warming In Mountain Regions Of The World, Mountain Research Institute, Nicolas Pepin, Raymond S. Bradley
Raymond S Bradley
"There is growing evidence that the rate of warming is amplified with elevation, such that high-mountain environments experience more rapid changes in temperature than environments at lower elevations. Elevation-dependent warming (EDW) can accelerate the rate of change in mountain ecosystems, cryospheric systems, hydrological regimes and biodiversity. Here we review important mechanisms that contribute towards EDW: snow albedo and surface-based feedbacks; water vapour changes and latent heat release; surface water vapour and radiative flux changes; surface heat loss and temperature change; and aerosols. All lead to enhanced warming with elevation (or at a critical elevation), and it is believed that combinations …
Winter Climate Extremes Over The Northeastern United States And Southeastern Canada And Teleconnections With Large-Scale Modes Of Climate Variability, Liang Ning, Raymond S. Bradley
Winter Climate Extremes Over The Northeastern United States And Southeastern Canada And Teleconnections With Large-Scale Modes Of Climate Variability, Liang Ning, Raymond S. Bradley
Raymond S Bradley
The relationship between winter climate extremes across the northeastern United States and adjacent parts of Canada and some important modes of climate variability are examined to determine how these circulation patterns are related to extreme events. Linear correlations between 15 extreme climate indices related to winter daily precipitation, maximum and minimum temperature, and three dominant large-scale patterns of climate variability [the North Atlantic Oscillation (NAO), Pacific–North American (PNA) pattern, and El Niño–Southern Oscillation (ENSO)] were analyzed for the period 1950–99. The mechanisms behind these teleconnections are analyzed by applying composite analysis to the geopotential height, sea level pressure (SLP), moisture …
Climate Change In The Northeastern Us: Regional Climate Model Validation And Climate Change Projections, Fangxing Fan, Raymond S. Bradley, Michael A. Rawlins
Climate Change In The Northeastern Us: Regional Climate Model Validation And Climate Change Projections, Fangxing Fan, Raymond S. Bradley, Michael A. Rawlins
Raymond S Bradley
A high resolution regional climate model (RCM) is used to simulate climate of the recent past and to project future climate change across the northeastern US. Different types of uncertainties in climate simulations are examined by driving the RCM with different boundary data, applying different emissions scenarios, and running an ensemble of simulations with different initial conditions. Empirical orthogonal functions analysis and K-means clustering analysis are applied to divide the northeastern US region into four climatologically different zones based on the surface air temperature (SAT) and precipitation variability. The RCM simulations tend to overestimate SAT, especially over the northern part …
Climatic Changes In Mountain Regions Of The American Cordillera And The Tropics: Historical Changes And Future Outlook, Henry F. Diaz, Raymond S. Bradley, Liang Ning
Climatic Changes In Mountain Regions Of The American Cordillera And The Tropics: Historical Changes And Future Outlook, Henry F. Diaz, Raymond S. Bradley, Liang Ning
Raymond S Bradley
We review some recent work regarding climatic changes in selected mountain regions, with particular attention to the tropics and the American Cordillera. Key aspects of climatic variability and trends in these regions are the amplification of surface warming trends with height, and the strong modulation of tempera¬ture trends by tropical sea surface temperature, largely controlled by changes in El Niño–Southern Oscillation on multiple time scales. Corollary aspects of these climate trends include the increase in a critical plant growth temperature threshold, a rise in the freezing level surface, and the possibility of enhanced subtropical drying. Anthropogenic global warming projections indicate …
Winter Precipitation Variability And Corresponding Teleconnections Over The Northeastern United States, Liang Ning, Raymond S. Bradley
Winter Precipitation Variability And Corresponding Teleconnections Over The Northeastern United States, Liang Ning, Raymond S. Bradley
Raymond S Bradley
The variability of winter precipitation over the northeastern United States and the corresponding teleconnections with five dominant large-scale modes of climate variability (Atlantic Multidecadal Oscillation, AMO; North Atlantic Oscillation, NAO; Pacific-North American pattern, PNA; Pacific Decadal Oscillation, PDO; and El Niño–Southern Oscillation, ENSO) were systemically analyzed in this study. Three leading patterns of winter precipitation were first generated by empirical orthogonal function (EOF) analysis. The correlation analysis shows that the first pattern is significantly correlated with PNA and PDO, the second pattern is significantly correlated with NAO and AMO, and the third pattern is significantly correlated with ENSO, PNA, and …
Locating Cryptotephra In Sediments Using Fluid Imaging Technology, Robert D'Anjou, Nicholas L. Balascio, Raymond S. Bradley
Locating Cryptotephra In Sediments Using Fluid Imaging Technology, Robert D'Anjou, Nicholas L. Balascio, Raymond S. Bradley
Raymond S Bradley
We report a new approach to locate and quantify cryptotephra in sedimentary archives using a continuously-imaging Flow Cytometer and Microscope (FlowCAM_). The FlowCAM rapidly photographs particles flowing in suspension past a microscope lens and performs semi-automated analysis of particle images. It has had primarily biological applications, although the potential sedimentological applications are numerous. Here we test the ability of this instrument to image irregularly shaped, vesicular glass shards and to screen sediment samples for the presence of cryptotephra. First, reference samples of basalt and rhyolite tephra (sieved <63>microns) were analyzed with the FlowCAM, demonstrating the ability of the instrument to …
Biogeochemical Evidence For Hydrologic Change During The Holocene In A Lake Sediment Record From Southeast Greenland, Nicholas L. Balascio, William J. D'Andrea, Raymond S. Bradley, Bianca B. Perren
Biogeochemical Evidence For Hydrologic Change During The Holocene In A Lake Sediment Record From Southeast Greenland, Nicholas L. Balascio, William J. D'Andrea, Raymond S. Bradley, Bianca B. Perren
Raymond S Bradley
Holocene paleoclimate records from Greenland help us understand the response of the Greenland Ice Sheet and regional oceanic and atmospheric circulation systems to natural climate variability in order to place recent changes in a longer-term perspective. Here biogeochemical analysis of a lake sediment core from southeast Greenland is used to define changes in moisture balance and runoff during the Holocene in a catchment near the margin of the Greenland Ice Sheet. A 1.6 m sediment core that spans the last 8.8 ka was recovered from Flower Valley Lake on Ammassalik Island. Magnetic susceptibility, diatoms, bulk biogeochemical properties (TOC, C/N, δ13Corg), …
Assessment Of Regional Climate Model Simulation Estimates Over The Northeast United States, M. A. Rawlins, Raymond S. Bradley, H. F. Diaz
Assessment Of Regional Climate Model Simulation Estimates Over The Northeast United States, M. A. Rawlins, Raymond S. Bradley, H. F. Diaz
Raymond S Bradley
Given the coarse scales of coupled atmosphere-ocean global climate models, regional climate models (RCMs) are increasingly relied upon for studies at scales appropriate for many impacts studies. We use outputs from an ensemble of RCMs participating in the North American Regional Climate Change Assessment Program (NARCCAP) to investigate potential changes in seasonal air temperature and precipitation between present (1971–2000) and future (2041–2070) time periods across the northeast United States. The models show a consistent modest cold bias each season and are wetter than observations in winter, spring, and summer. Agreement in spatial variability and pattern correlation is good for air …
Proxy-To-Proxy Calibration: Increasing The Temporal Resolution Of Quantitative Climate Reconstructions, Lucien Von Gunten, William J. D'Andrea, Raymond S. Bradley, Yongsong Huang
Proxy-To-Proxy Calibration: Increasing The Temporal Resolution Of Quantitative Climate Reconstructions, Lucien Von Gunten, William J. D'Andrea, Raymond S. Bradley, Yongsong Huang
Raymond S Bradley
No abstract provided.
Evaluating Holocene Climate Change In Northern Norway Using Sediment Records From Two Contrasting Lake Systems., Nicholas L. Balascio, Raymond S. Bradley
Evaluating Holocene Climate Change In Northern Norway Using Sediment Records From Two Contrasting Lake Systems., Nicholas L. Balascio, Raymond S. Bradley
Raymond S Bradley
We analyzed Holocene sedimentary records from two lakes in the Lofoten Islands, northern Norway to evaluate environmental changes during the Holocene related to northern North Atlantic climate dynamics. The lakes are located in different geomorphological settings, and thus provide a contrast in their response to regional climate change. Environmental changes at both lakes were interpreted based on magnetic susceptibility, organic-matter flux, C/N, d13 Corg , Ti concentrations, and mass accumulation rates. Chronologies were established using 16 AMS radiocarbon dates, and average deposition rates in both environments are higher than 0.2 mm/year throughout the Holocene. At Vikjordvatnet, sedimentary geochemical properties define …
What Can We Learn From Past Warm Climates?, Raymond S. Bradley
What Can We Learn From Past Warm Climates?, Raymond S. Bradley
Raymond S Bradley
With limited political action to control fossil fuel use and associated greenhouse gas emissions, there is increasing emphasis on preparing for inevitable climate changes. But what changes should the world plan for? Model simulations provide some guidance about expected future climate scenarios, but we can also learn from past experience. Although there are no episodes in the past that are strictly comparable to the future, which is a world in which climate is modulated by human activities, there were warm periods in the past which resulted from other forcing factors. There are some lessons we can learn from paleoclimate records …
Biogeochemical Evidence For Prehistoric Human Impacts On The Environment In Northwestern Norway, Raymond S. Bradley, Robert D'Anjou, Nicholas L. Balascio, David B. Finkelstein
Biogeochemical Evidence For Prehistoric Human Impacts On The Environment In Northwestern Norway, Raymond S. Bradley, Robert D'Anjou, Nicholas L. Balascio, David B. Finkelstein
Raymond S Bradley
Disentangling the effects of climate change and anthropogenic activities on the environment is a major challenge in paleoenvironmental research. Here, we used fecal sterols and other biogeochemical compounds in lake sediments from northern Norway to identify both natural and anthropogenic signals of environmental change during the late Holocene. The area was first occupied by humans and their grazing animals at ∼2,250 ± 75 calendar years before 1950 AD (calendar years before present). The arrival of humans is indicated by an abrupt increase in coprostanol (and its epimer epicoprostanol) in the sediments and an associated increase in 5β-stigmastanol (and 5β-epistigmastanol), which …
A Mild Little Ice Age And Unprecedented Warmth In An 1800 Year Record From Svalbard, William J. D'Andrea, Raymond S. Bradley, David Vaillencourt, Nicholas L. Balascio, Al Werner, Steve Roof, Michael J. Retelle
A Mild Little Ice Age And Unprecedented Warmth In An 1800 Year Record From Svalbard, William J. D'Andrea, Raymond S. Bradley, David Vaillencourt, Nicholas L. Balascio, Al Werner, Steve Roof, Michael J. Retelle
Raymond S Bradley
The Arctic region is subject to a great amplitude of climate variability and is currently undergoing large-scale changes due in part to anthropogenic global warming. Accurate projections of future change depend on anticipating the response of the Arctic climate system to forcing, and understanding how the response to human forcing will interact with natural climate variations. The Svalbard Archipelago occupies an important location for studying patterns and causes of Arctic climate variability; however, available paleoclimate records from Svalbard are of restricted use due to limitations of existing climate proxies. Here we present a sub-decadal- to multidecadal-scale record of summer temperature …
Climate Change In Central America And Mexico: Regional Climate Model Validation And Climate Change Projections, Ambarish V. Karmalkar, Raymond S. Bradley, Henry F. Diaz
Climate Change In Central America And Mexico: Regional Climate Model Validation And Climate Change Projections, Ambarish V. Karmalkar, Raymond S. Bradley, Henry F. Diaz
Raymond S Bradley
Central America has high biodiversity, it harbors high-value ecosystems and it’s important to provide regional climate change information to assist in adaptation and mitigation work in the region. Here we study climate change projections for Central America and Mexico using a regional climate model. The model evaluation shows its success in simulating spatial and temporal variability of temperature and precipitation and also in capturing regional climate features such as the bimodal annual cycle of precipitation and the Caribbean low-level jet. A variety of climate regimes within the model domain are also better identified in the regional model simulation due to …
Where Do We Stand On Global Warming?, Raymond S. Bradley
Where Do We Stand On Global Warming?, Raymond S. Bradley
Raymond S Bradley
Global temperatures have risen by ~0.8°C since the end of the 19th century. This increase has not been linear, as there have been periods when temperatures were stable for short periods before rising once again. The reasons for these changes in the rate of temperature rise are related to anthropogenic factors (sulphate aerosol pollution versus greenhouse gas inputs to the atmosphere) as well as to natural factors (volcanic eruptions, solar irradiance variations, El Ni.o/Southern Oscillation [ENSO] fluctuations, etc). Over the last decade or so, temperatures have not risen at the same rate as in previous decades, and this has led …
Natural Archives, Changing Climates, Raymond S. Bradley
Natural Archives, Changing Climates, Raymond S. Bradley
Raymond S Bradley
Climatic changes have occurred throughout human history, but instrumental measurements do not provide us with a very long perspective on climate variations. In many regions, instrumental records only extend back a century or two. To understand the longer-term variability of the climate system, we rely on natural archives— sediments, ice caps, peat bogs, cave deposits, banded corals and tree rings—in which a record of past changes in climate has been preserved. They are a treasure trove of the climatic and environmental history of the planet and provide information about factors that may have caused the climate to change, such as …
Distal Tephra Found In A Viking Boathouse: The Potential For Tephrochronology In Reconstructing The Iron Age In Norway, Nicholas L. Balascio, Stephen Wickler, L E. Narmo, Raymond S. Bradley
Distal Tephra Found In A Viking Boathouse: The Potential For Tephrochronology In Reconstructing The Iron Age In Norway, Nicholas L. Balascio, Stephen Wickler, L E. Narmo, Raymond S. Bradley
Raymond S Bradley
Distal tephra deposits from Icelandic volcanic eruptions have been found in Norway and can be used to precisely date a variety of sedimentary environments. Tephrochronology has not yet been applied to archaeological investigations in Norway because tephra are generally not found as visible layers, but are present as very low concentrations of glass shards (i.e. cryptotephra). In this study, we present results from the analysis of cryptotephras found in an Iron Age boathouse in northern Norway. The boathouse was associated with the chieftain center at Borg on Vestvågøy in the Lofoten Islands. In 2003, a trench was excavated and the …
High-Resolution Paleoclimatology, Raymond S. Bradley
High-Resolution Paleoclimatology, Raymond S. Bradley
Raymond S Bradley
High resolution paleoclimatology involves studies of natural archives as proxies for past climate variations at a temporal scale that is comparable to that of instrumental data. In practice, this generally means annually resolved records, from tree rings, ice cores, banded corals, laminated speleothems and varved sediments. New analytical techniques offer many unexplored avenues of research in high resolution paleoclimatology. However, critical issues involving accuracy of the chronology, reproducibility of the record, frequency response to forcing and other factors, and calibration of the proxies remain. Studies of proxies at high resolution provide opportunities to examine the frequency and magnitude of extreme …
A Multi-Proxy Approach To Assessing Isolation Basin Stratigraphy From The Lofoten Islands, Norway, Nicholas L. Balascio, Zhaohui Zhang, Raymond S. Bradley, Bianca B. Perren, Svein-Olaf Dahl, Jostein Bakke
A Multi-Proxy Approach To Assessing Isolation Basin Stratigraphy From The Lofoten Islands, Norway, Nicholas L. Balascio, Zhaohui Zhang, Raymond S. Bradley, Bianca B. Perren, Svein-Olaf Dahl, Jostein Bakke
Raymond S Bradley
This study takes a comprehensive approach to characterizing the isolation sequence of Heimerdalsvatnet, a coastal lake in the Lofoten Islands, northern Norway. We use established methods and explore new techniques to assess changes in marine influence. Bathymetric and sub-bottom profiles were acquired to examine basin-wide sedimentation and a 5.8 m sediment core spanning the last 7800 cal yr BP was analyzed. We measured magnetic susceptibility, bulk organic matter properties, molecular biomarkers, diatom assemblages, and elemental profiles acquired by scanning X-ray fluorescence. These characteristics of the sediment reflect detailed changes in salinity and water column conditions as the lake was progressively …
An Analysis Of Past And Future Changes In The Ice Cover Of Two High-Arctic Lakes Based On Synthetic Aperture Radar (Sar) And Landsat Imagery, Timothy L. Cook, Raymond S. Bradley
An Analysis Of Past And Future Changes In The Ice Cover Of Two High-Arctic Lakes Based On Synthetic Aperture Radar (Sar) And Landsat Imagery, Timothy L. Cook, Raymond S. Bradley
Raymond S Bradley
Space-borne remotely sensed data can provide valuable insight into cryospheric processes in remote high-latitude regions for which direct observations are limited. In this study we use synthetic aperture radar (SAR) and Landsat imagery to evaluate recent changes in the ice cover of Upper and Lower Murray Lakes (81°20′N, 69°30′W) on Ellesmere Island, Nunavut, Canada. These data highlight changes in ice conditions that have occurred over the past decade and provide a means for assessing the likely impacts of rising temperatures on future lake-ice conditions. Under current (1997–2007) climatic conditions the Murray Lakes average several weeks of ice-free conditions in August …
Changes In Extreme Climate Indices For The Northeastern United States, 1870-2006, Paula J. Brown, Raymond S. Bradley, Frank T. Keimig
Changes In Extreme Climate Indices For The Northeastern United States, 1870-2006, Paula J. Brown, Raymond S. Bradley, Frank T. Keimig
Raymond S Bradley
The northeastern United States is one of the most variable climates in the world, and how climate extremes are changing is critical to populations, industries, and the environment in this region.Along-term (1870–2005) temperature and precipitation dataset was compiled for the northeastern United States to assess how the climate has changed. Adjustments were made to daily temperatures to account for changes in mean, variance, and skewness resulting from inhomogeneities, but precipitation data were not adjusted. Trends in 17 temperature and 10 precipitation indices at 40 stations were evaluated over three time periods—1893–2005, 1893– 1950, and 1951–2005—and over 1870–2005 for a subset …
Recent Changes In Freezing Level Heights In The Tropics With Implications For The Deglacierization Of High Mountain Regions, Raymond S. Bradley, F. Keimig, H. F. Diaz, D. R. Hardy
Recent Changes In Freezing Level Heights In The Tropics With Implications For The Deglacierization Of High Mountain Regions, Raymond S. Bradley, F. Keimig, H. F. Diaz, D. R. Hardy
Raymond S Bradley
The height of the freezing level in the tropical atmosphere (the free air 0°C isotherm) has increased across most of the region, particularly in the outer Tropics. In the tropical Andes, south of the Equator, high elevation surface temperatures and upper air data show a similar trend in temperature, of ∼0.1°C/decade over the last 50 years. Meteorological observations at 5680 m on the summit of the Quelccaya Ice Cap, the largest ice mass in the Tropics, indicate that daily maximum temperatures often exceed 0°C from October–May, and rise well above freezing for much of the year around the ice cap …
Evidence For A Widespread Climatic Anomaly At Around 9.2 Ka Before Present, Dominik Fleitmann, Manfred Mudelsee, Stephen J. Burns, Raymond S. Bradley, Jan Kramers, Albert Matter
Evidence For A Widespread Climatic Anomaly At Around 9.2 Ka Before Present, Dominik Fleitmann, Manfred Mudelsee, Stephen J. Burns, Raymond S. Bradley, Jan Kramers, Albert Matter
Raymond S Bradley
No abstract provided.
Proxy-Based Reconstructions Of Hemispheric And Global Surface Temperature Variations Over The Past Two Millennia, M. E. Mann, Z. Zhang, M. K. Hughes, Raymond S. Bradley, S. K. Miller, S. Rutherford, F. Ni
Proxy-Based Reconstructions Of Hemispheric And Global Surface Temperature Variations Over The Past Two Millennia, M. E. Mann, Z. Zhang, M. K. Hughes, Raymond S. Bradley, S. K. Miller, S. Rutherford, F. Ni
Raymond S Bradley
Following the suggestions of a recent National Research Council report [NRC (National Research Council) (2006) Surface Temperature Reconstructions for the Last 2,000 Years (Natl Acad Press, Washington, DC).], we reconstruct surface temperature at hemispheric and global scale for much of the last 2,000 years using a greatly expanded set of proxy data for decadal-to-centennial climate changes, recently updated instrumental data, and complementary methods that have been thoroughly tested and validated with model simulation experiments. Our results extend previous conclusions that recent Northern Hemisphere surface temperature increases are likely anomalous in a long-term context. Recent warmth appears anomalous for at least …
The Younger Dryas And The Sea Of Ancient Ice, Raymond S. Bradley, John H. England
The Younger Dryas And The Sea Of Ancient Ice, Raymond S. Bradley, John H. England
Raymond S Bradley
We propose that prior to the Younger Dryas period, the Arctic Ocean supported extremely thick multi-year fast ice overlain by superimposed ice and firn. We re-introduce the historical term paleocrystic ice to describe this. The ice was independent of continental (glacier) ice and formed a massive floating body trapped within the almost closed Arctic Basin, when sea-level was lower during the last glacial maximum. As sea-level rose and the Barents Sea Shelf became deglaciated, the volume of warm Atlantic water entering the Arctic Ocean increased, as did the corresponding egress, driving the paleocrystic ice towards Fram Strait. New evidence shows …
Climate Change Scenario For Costa Rican Montane Forests, A. V. Karmalkar, Raymond S. Bradley, H. F. Diaz
Climate Change Scenario For Costa Rican Montane Forests, A. V. Karmalkar, Raymond S. Bradley, H. F. Diaz
Raymond S Bradley
Tropical montane cloud forests are characterized by persistent immersion in clouds, an important source of moisture during the dry season. Future changes in temperature and precipitation could alter cloud cover at the vegetation level and seriously affect mountain ecosystems. A regional climate modeling study that focuses on changes in the distributions of temperature and precipitation in Costa Rica shows, in general, an increase in temperature and a decrease in precipitation under the A2 scenario. At high elevations, warming is amplified and future temperature distribution lies outside the range of present-day distribution. Compared to the Caribbean side, temperature changes are greater …
Variations Of Twentieth-Century Temperature And Precipitation Extreme Indicators In The Northeast United States, Michael L. Griffiths, Raymond S. Bradley
Variations Of Twentieth-Century Temperature And Precipitation Extreme Indicators In The Northeast United States, Michael L. Griffiths, Raymond S. Bradley
Raymond S Bradley
An examination of five temperature and five precipitation extreme indicators reveals an increase in both temperature and precipitation extremes over the 1926–2000 period in the northeast United States, with most of this increase occurring over the past four decades. Empirical orthogonal function (EOF) analysis of winter frost days (FD) and warm nights (TN90) and also winter consecutive dry days (CDD) and very wet days (R95T) over the 1950–2000 period reveals that some of the variability associated with changes in these extremes may be explained by variations in the Arctic Oscillation (AO), El Niño–Southern Oscillation (ENSO), and Pacific–North American (PNA) pattern. …
Threats To Water Supplies In The Tropical Andes, Raymond S. Bradley, Mathias Vuille, Henry F. Diaz, Walter Vergara
Threats To Water Supplies In The Tropical Andes, Raymond S. Bradley, Mathias Vuille, Henry F. Diaz, Walter Vergara
Raymond S Bradley
Climate models predict that greenhouse warming will cause temperatures to rise faster at higher than at lower altitudes. In the tropical Andes, glaciers may soon disappear, with potentially grave consequences for water supplies.
Solar Modulation Of Little Ice Age Climate In The Tropical Andes, P. J. Polissar, M. B. Abbott, A. P. Wolfe, M. Bezada, V. Rull, Raymond S. Bradley
Solar Modulation Of Little Ice Age Climate In The Tropical Andes, P. J. Polissar, M. B. Abbott, A. P. Wolfe, M. Bezada, V. Rull, Raymond S. Bradley
Raymond S Bradley
The underlying causes of late-Holocene climate variability in the tropics are incompletely understood. Here we report a 1,500-year reconstruction of climate history and glaciation in the Venezuelan Andes using lake sediments. Four glacial advances occurred between anno Domini (A.D.) 1250 and 1810, coincident with solar-activity minima. Temperature declines of −3.2 ± 1.4°C and precipitation increases of ≈20% are required to produce the observed glacial responses. These results highlight the sensitivity of high-altitude tropical regions to relatively small changes in radiative forcing, implying even greater probable responses to future anthropogenic forcing.
Proxy-Based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity To Method, Predictor Network, Target Season, And Target Domain, S. Rutherford, M. E. Mann, T. J. Osborne, Raymond S. Bradley, K. R. Briffa, M. K. Hughes, P. D. Jones
Proxy-Based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity To Method, Predictor Network, Target Season, And Target Domain, S. Rutherford, M. E. Mann, T. J. Osborne, Raymond S. Bradley, K. R. Briffa, M. K. Hughes, P. D. Jones
Raymond S Bradley
Results are presented from a set of experiments designed to investigate factors that may influence proxy-based reconstructions of large-scale temperature patterns in past centuries. The factors investigated include 1) the method used to assimilate proxy data into a climate reconstruction, 2) the proxy data network used, 3) the target season, and 4) the spatial domain of the reconstruction. Estimates of hemispheric-mean temperature are formed through spatial averaging of reconstructed temperature patterns that are based on either the local calibration of proxy and instrumental data or a more elaborate multivariate climate field reconstruction approach. The experiments compare results based on the …