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1. Introduction Paleoclimate is a larger and grander topic than Climate Variability and Predictability (CLIVAR), the subject of this entire special section. It encompasses a far greater range of time scales and a greater range of physical and biogeochemical processes. A decade ago, the mismatch between computing capability and the length of integrations demanded by most paleoclimate problems severely limited what could be accomplished with general circulation class models. The great expansion
1. Introduction Paleoclimate is a larger and grander topic than Climate Variability and Predictability (CLIVAR), the subject of this entire special section. It encompasses a far greater range of time scales and a greater range of physical and biogeochemical processes. A decade ago, the mismatch between computing capability and the length of integrations demanded by most paleoclimate problems severely limited what could be accomplished with general circulation class models. The great expansion
1. Introduction A general goal of paleoclimatology is to use paleoclimate observations, which are sparser and noisier than direct observations, to characterize preinstrumental climate variability. Paleoclimate observations involve, for example, using δ 18 O of coral aragonite to measure a combination of temperature during calcification and seawater δ 18 O value, while direct observations would be made, for instance, by using a thermometer to measure bucket SST. Ideally, the design of sampling
1. Introduction A general goal of paleoclimatology is to use paleoclimate observations, which are sparser and noisier than direct observations, to characterize preinstrumental climate variability. Paleoclimate observations involve, for example, using δ 18 O of coral aragonite to measure a combination of temperature during calcification and seawater δ 18 O value, while direct observations would be made, for instance, by using a thermometer to measure bucket SST. Ideally, the design of sampling
, particularly for streamflow). This is clearly insufficient to capture variability occurring on a multidecadal time scale or longer. Recent advances in the collection and analysis of paleoclimate information have, however, provided insights into historical environmental events and processes prior to the availability of instrumental records ( Bradley and Jones 1995 ; Cronin 2010 ). This information has enabled a greater understanding of long-term environmental variability and associated hydroclimatic risks
, particularly for streamflow). This is clearly insufficient to capture variability occurring on a multidecadal time scale or longer. Recent advances in the collection and analysis of paleoclimate information have, however, provided insights into historical environmental events and processes prior to the availability of instrumental records ( Bradley and Jones 1995 ; Cronin 2010 ). This information has enabled a greater understanding of long-term environmental variability and associated hydroclimatic risks
.e., the relative influence of the remote dynamical mechanism on regional and local climates) are not perfectly stationary in time ( Mullan 1995 ; Nicholls et al. 1996 ; Verdon and Franks 2006 ; Risbey et al. 2009 ). Reconstructions of the preinstrumental climate using paleoclimate proxies have utilized teleconnection patterns to estimate remote (local) climate variations from a local (remote) source. For example, past variations in ENSO have been inferred from tree-ring widths from New Zealand and
.e., the relative influence of the remote dynamical mechanism on regional and local climates) are not perfectly stationary in time ( Mullan 1995 ; Nicholls et al. 1996 ; Verdon and Franks 2006 ; Risbey et al. 2009 ). Reconstructions of the preinstrumental climate using paleoclimate proxies have utilized teleconnection patterns to estimate remote (local) climate variations from a local (remote) source. For example, past variations in ENSO have been inferred from tree-ring widths from New Zealand and
this paper, we quantify Holocene paleoclimates across northern Canada between 50° and 70°N, encompassing the boreal and low Arctic regions. Through this determination of regional-scale patterns of climate variability we can provide a context for global warming. To accomplish this, we use a network of fossil pollen records that has the advantage of reducing the temporal and spatial uncertainties associated with site-specific uncertainties. The data were extracted from the North American Pollen
this paper, we quantify Holocene paleoclimates across northern Canada between 50° and 70°N, encompassing the boreal and low Arctic regions. Through this determination of regional-scale patterns of climate variability we can provide a context for global warming. To accomplish this, we use a network of fossil pollen records that has the advantage of reducing the temporal and spatial uncertainties associated with site-specific uncertainties. The data were extracted from the North American Pollen
1. Introduction Information recorded in paleoclimate archives reveals that the twentieth century does not represent the full range of drought variability experienced in western North America (WNA) during the last millennium (e.g., Woodhouse and Overpeck 1998 ; Stahle et al. 2007 ; Cook et al. 2004 ; Meko et al. 2007 ). Prolonged droughts comprise a source of climate risk in this region and elsewhere ( Woodhouse and Overpeck 1998 ; Shanahan et al. 2009 ; Buckley et al. 2010 ; Haug et al
1. Introduction Information recorded in paleoclimate archives reveals that the twentieth century does not represent the full range of drought variability experienced in western North America (WNA) during the last millennium (e.g., Woodhouse and Overpeck 1998 ; Stahle et al. 2007 ; Cook et al. 2004 ; Meko et al. 2007 ). Prolonged droughts comprise a source of climate risk in this region and elsewhere ( Woodhouse and Overpeck 1998 ; Shanahan et al. 2009 ; Buckley et al. 2010 ; Haug et al
availability of proxy data has restricted these studies to the extratropics and/or periods shorter than 1000 years ( Hegerl et al. 2003 , 2007a ). Thus our knowledge of the role of climate forcings over the past 1500 years remains limited, particularly for regions that lie outside the northern extratropics. b. Paleoclimate data–model comparison Paleoclimate proxies and climate models constitute two contrasting and yet complementary sources of information on past climates. Both approaches can be applied
availability of proxy data has restricted these studies to the extratropics and/or periods shorter than 1000 years ( Hegerl et al. 2003 , 2007a ). Thus our knowledge of the role of climate forcings over the past 1500 years remains limited, particularly for regions that lie outside the northern extratropics. b. Paleoclimate data–model comparison Paleoclimate proxies and climate models constitute two contrasting and yet complementary sources of information on past climates. Both approaches can be applied
1. Introduction Paleoclimate reconstructions of tropical sea surface temperature (SST) fields are used to characterize the range of tropical climate variability and may improve our understanding of the role that the tropics play in global climate change. These reconstructions use a variety of proxy records ranging from tree rings and ice cores to corals and marine sediments in both the tropics and extratropics (e.g., Stahle et al. 1998 ; Evans et al. 2002 ). Although some of these proxies
1. Introduction Paleoclimate reconstructions of tropical sea surface temperature (SST) fields are used to characterize the range of tropical climate variability and may improve our understanding of the role that the tropics play in global climate change. These reconstructions use a variety of proxy records ranging from tree rings and ice cores to corals and marine sediments in both the tropics and extratropics (e.g., Stahle et al. 1998 ; Evans et al. 2002 ). Although some of these proxies
simulate persistent and severe droughts across the NH extratropics that are consistent with the paleoclimate record? 2) If so, do CGCMs suggest that the characteristics of these droughts will change in the future? Critically, our novel and comprehensive approach to assessing future drought risk provides new insights into the physical mechanisms underlying persistent and severe droughts and the ability of state-of-the-art CGCMs to reproduce them. 2. Methods a. Paleoclimate record We employ the North
simulate persistent and severe droughts across the NH extratropics that are consistent with the paleoclimate record? 2) If so, do CGCMs suggest that the characteristics of these droughts will change in the future? Critically, our novel and comprehensive approach to assessing future drought risk provides new insights into the physical mechanisms underlying persistent and severe droughts and the ability of state-of-the-art CGCMs to reproduce them. 2. Methods a. Paleoclimate record We employ the North
1. Introduction Clastic successions record sedimentary processes (e.g., fluvial, tidal, wave) that are responsible for facies distribution and architecture. These successions can also record paleoclimate information critical for understanding the depositional environment and paleogeography. For example, cycles in sedimentary processes may indicate wet and dry seasons. Such changes associated with seasonal fluctuations of river discharge have been described from modern systems (e.g., Sisulak
1. Introduction Clastic successions record sedimentary processes (e.g., fluvial, tidal, wave) that are responsible for facies distribution and architecture. These successions can also record paleoclimate information critical for understanding the depositional environment and paleogeography. For example, cycles in sedimentary processes may indicate wet and dry seasons. Such changes associated with seasonal fluctuations of river discharge have been described from modern systems (e.g., Sisulak
