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Rate and Magnitude of Past Global Climate Changes
Abstract
ABSTRACT•Existing data indicate that the Earth's climate is probably warming. Politicians and the media typically assume this warming is the result of human activity. This article summarizes previous climate changes to test the validity of assigning causality to human activity.Records of glacial advances and retreats indicate relative summer temperature. Lacustrine and subaerial sediments afford a record of glacier advances and retreats from the Pleistocene to the present time. Palynology offers a record of species succession in response to climate changes. Dendrochronology is another indicator of summer temperature. Isotope paleontology offers a measurement of temperature at the time of marine sediment deposition, and isotopic evaluation of continental ice is an indicator of temperature at the time of precipitation. Anthropologic sources contain significant climate data such as information about villages overrun by glaciers, open-ocean iceberg density, or harbors filled with ice. Today, scientists are capable of direct measurement of climatic conditions.These sources record continual changes in climate. Broadly, the temperature changed 15 to 20°C from the Paleocene to the Neogene. Perhaps, there was as much as another 10°C change in the Pleistocene. Correlative data from North America, Greenland, and Scandinavia indicate many climate changes were truly global in scope. Although it is difficult to develop precise paleothermometry, qualitative evaluations indicate sudden and dramatic changes in climate. Some are perhaps as great as a change from conditions warmer than today to a full glacial climate in as little as 100 years. The converse can be true. Current data indicate a trend of change that is substantially severe but no greater in rate or magnitude, and probably less in both, than many changes that have occurred in the past.
... Geological field investigations show that within the past 4000 years Devils Lake has gone completely dry four times, and spilled over to the Red River of the North three times (Bluemle et al. 1999). The natural condition for the lake is to be rising toward overflow to the neighbouring Stump Lake or Sheyenne River, or falling toward desiccation as a dry lake bed (Bluemle et al. 1999). ...
... Geological field investigations show that within the past 4000 years Devils Lake has gone completely dry four times, and spilled over to the Red River of the North three times (Bluemle et al. 1999). The natural condition for the lake is to be rising toward overflow to the neighbouring Stump Lake or Sheyenne River, or falling toward desiccation as a dry lake bed (Bluemle et al. 1999). Widely fluctuating lake levels are the normal condition for the lake, while long periods of stable lake levels are uncommon. ...
... The large fluctuations in reconstructed lake level during the late Holocene (Bluemle et al. 1999), and observed lake level during the late 20th century (Fig. 2), are the result of special characteristics of the Devils Lake water balance. Devils Lake is an example of an amplifier terminal lake, a term first proposed by Street (1980) following the general classification of lake water budgets presented by Szesztay (1974). ...
Devils Lake, a terminal lake in eastern North Dakota, has risen more than 9 m between 1992 and 2013, producing a 286% increase in lake area, and causing more than US$1 billion in direct damages. An annual volumetric lake water budget is developed from monthly hydroclimatological variables for the period 1951–2010 to investigate the rapid lake expansion. The lake is an amplifier terminal lake in which long-term climatic changes are amplified by positive feedback mechanisms, causing the lake to transition from a precipitation-dominated to a runoff-dominated water budget. Factors specific to the Devils Lake Basin further amplify this positive feedback relationship. These include principles of fill-spill hydrology that operate between individual sub-basins within the closed basin, and between the innumerable wetland complexes within each sub-basin. These factors create a pronounced non-stationary precipitation–runoff relationship in the basin during both long-term wetting and drying phases.
... Devils Lake (DL), located in northeastern North Dakota, USA (Fig. 1), is a typical example of a closed lake system (9800 km 2 watershed) experiencing profound water level fluctuations in both recorded recent and geologic history. Since its glacial origin 10,000 years ago, DL has exceeded its maximum overspill elevation (444.4 m amsl) at least 4-6 times (Bluemle et al. 1999;Haskell et al. 1996). Based on United States Geological Survey (USGS) recorded data, DL fluctuated by nearly 16.5 m since 1867. ...
... Since 1991, DL rose by 10 m, increasing its surface area by a factor of four (from 185 to 772 km 2 ) and its volume by a factor of six (from 0.74 to 4.4 km 3 ). These water fluctuations, both current and historic, are mainly attributed to the effects of long-term climatic variability in the region (Bluemle et al. 1999;Haskell et al. 1996;Johnson et al. 2005;Murphy et al. 1997), with others speculating about limited or negligible impacts from groundwater recharge, land cover modifications and agricultural practices (Pusc 1993;Swenson and Colby 1955;Wiche et al. 1986). ...
The combined effects of climate and land-use change have changed both the hydrology and management of endorheic watersheds globally. Devils Lake (DL), North Dakota, USA, has risen nearly 10 m since 1991, resulting in a costly, lengthy and litigious water management issue in the region. With more than 1 billion US dollars already spent in mitigation, DL is less than 2 m from its uncontrolled overspill to the nearby Sheyenne River, which could lead to mounting economic, environmental and social costs. While previous studies have generally attributed the changes in the hydrology of DL to the current wet spell, the impacts of land-use changes have not been investigated. Using a hydrological model, here we develop four land-use alternatives driven by market and policy conditions in the DL watershed and investigate their effects on DL hydrology and overspill probability under historic and changed climates. Land-use scenarios under an ensemble of statistically downscaled general circulation model projections indicate a higher overspill risk (7.4–17.0 vs. 0–2 %) under historical climate. Incentivized grass and alfalfa scenarios were able to moderate the hydrological implications to DL under a changed climate, indicating their potential companion roles in DL flood mitigation strategies.
... ages and the luminescence ages would be reduced by 10-20% if the longterm moisture content had been higher than the arbitrary moisture content used in our age calculations . Higher moisture content would not be surprising because most of the late Pleistocene was markedly cooler (and likely wetter) than either the Holocene or historical conditions (Bluemle et al . 2001) . ...
... with basins south of Socorro, New Mexico Williams and Cole 2007) . The long aggradation period between about 1 .6 Ma and 1 .2 Ma probably involved many subcycles of incision and filling related to earth-orbital variations, climate fluctuation, and cooling, and the onset of more stable Pleistocene glacial-interglacial cycles (Crowley and North 1991;Bluemle et al . 2001) . ...
Results from luminescence dating on 13 samples from the Albuquerque area show that major-drainage fluvial deposits represent significant periods of aggradation that formed paired, correlatable terraces on the east and west margins of the Rio Grande valley. The youngest terrace fills (Primero Alto) formed during late Pleistocene as a result of streamflow variations with climate cooling during Marine Oxygen-Isotope Stage 3; our ages suggest aggradation of the upper part of the fill occurred at about 47-40 ka. Deposits of the second (Segundo Alto) terraces reached maximum height during climate cooling in the early part of Marine Oxygen-Isotope Stage 5 as late as 90-98 ka (based on dated basalt flows). Our luminescence ages show considerable scatter and tend to be younger (range from 63 ka to 162 ka). The third (Tercero Alto) and fourth (Cuarto Alto) terraces are dated on the basis of included volcanic tephra. Tercero Alto terrace-fill deposits contain the Lava Creek B tephra (639 ka), and Cuarto Alto terrace-fill deposits contain tephra of the younger Bandelier Tuff eruption (1.22 Ma), the Cerro Toledo Rhyolite (1.47 Ma), and the older Bandelier Tuff eruption (1.61 Ma). These periods of aggradation culminated in fluvial terraces that are preserved at maximum heights of 360 ft (Cuarto Alto), 300 ft (Tercero Alto), 140 ft (Segundo Alto), and 60 ft (Primero Alto) above the modern flood-plain. Despite lithologic differences related to local source-area contributions, these terracefill deposits can be correlated across the Rio Grande and up- and down-valley for tens of miles based on maximum height of the terrace above the modern floodplain.
... Previous studies have attributed the DL waterlevel fluctuations to the effects of long-term climatic variability in the region (Haskell et al., 1996;Murphy et al., 1997;Bluemle et al., 1999;Johnson et al., 2005). Since the 1980s, the DL region has experienced a wet climate phase that has led to an unprecedented rise in DL water levels (Vecchia, 2002). ...
... Vecchia (2011) assumed that the regional pattern of increased annual precipitation along the Great Plains corridor since 1980 (Hoerling et al., 2010) will extend to the following 10-60 years (Vecchia, 2008). Consequently, future precipitation, lake evaporation, and inflow data were generated using a floating baseline climate: 1980-1999in Vecchia (2002), 1980-2006in Vecchia (2008), and 1981-2009in Vecchia (2011. Some of these fluctuations in the projections of DL overspill may be due to the floating baseline period. ...
Terminal lakes are impacted by regional changes in climate. Devils Lake (DL), North Dakota, United States (U.S.), is a case in which a prolonged shift in the precipitation pattern resulted in a 10-m water-level rise over the past two decades, which cost over one billion U.S. dollars in mitigation. Currently, DL is 1.5 m from an uncontrolled overspill to the nearby Sheyenne River, which could lead to unprecedented environmental , social, and economic costs. Water outlets recently implemented in the lake to slow the water-level rise and prevent an uncontrolled overspill are subject to significant concerns over the introduction of invasive species and downstream water quality. We developed a hydrological model of the DL basin using the soil and water assessment tool and analyzed DL's overspill probability using an ensemble of statistically downscaled General Circulation Model (GCM) projections of the future climate. The results indicate a significant likelihood (7.3-20.0%) of overspill in the next few decades in the absence of outlets; some members of the GCM integration ensemble suggest an exceedance probability of over 85.0 and 95.0% for the 2020s and 2050s, respectively. Full-capacity outlets radically reduce the probability of DL overspill and are able to partially mitigate the problem by decreasing the average lake level by approximately 1.9 and 1.5 m in the 2020s and 2050s, respectively.
... A reconstruction of the water-surface elevation history for Devils Lake by Bluemle et al. (1999) indicated that, although the lake is considered a perennial closed lake, it might have become dry four times, spilled into Stump Lake five times, and discharged to the Sheyenne River three times over the past 4000 yrs. Results from paleolimnological studies based upon a variety of proxy indicators also show that regional vegetation and lake salinity have changed rapidly and often over the past 12,000 yrs. ...
... Regional soil-moisture storage has reached such a high level that the soil's capacity to serve as a buffer against precipitation input has been reduced, resulting in an increased runoff response as the wet spell has progressed. Water-surface elevation fluctuations at Devils Lake during the past century have been entirely within the range of natural lake-level variability (Bluemle et al., 1999), and are not unprecedented with respect to the lake water-level history during the past 12,000 yrs. prior to European settlement and subsequent land-cover disturbance. ...
The Devils Lake Basin of North Dakota, an interior drainage basin located within a dry, subhumid environment, has experienced pervasive flood conditions since the 1993 onset of a wet spell of unprecedented magnitude and duration. This unique natural-hazard environment has resulted in flooding from both the expansion of the surface area of the basin's terminal lakes (Devils Lake and Stump Lake) and increases in the number and size of rural wetlands. To assess the relative extent of both terminal lake and rural wetland flooding, we focused on Nelson County, which contains Stump Lake and is representative of other counties in the basin. Remotely sensed data acquired by Landsat Thematic Mapper was used to map open-water extent in 2001, and results were compared to 1992 land-cover data provided by the United States Geological Survey (USGS). Our analysis indicates a 53% increase in the size of Stump Lake and a 426% increase in the area of rural wetland ponds. Stump Lake flooding is spatially restricted and has had limited impact upon the surrounding lakeshore environment. Rural wetland flooding is pervasive and has a deleterious effect upon the region's agricultural economic base.
... Rising concern about the effects of current environmental change has led to increased interest in past environments (Bluemle et al., 1999;Trotter et al., 2002). However, the scarcity of historical records and information from long-term monitoring programs has necessitated the reconstruction of past environmental conditions from proxy records of climate and geomorphology (e.g., Bluemle et al., 1999;Mann, 2002). ...
... Rising concern about the effects of current environmental change has led to increased interest in past environments (Bluemle et al., 1999;Trotter et al., 2002). However, the scarcity of historical records and information from long-term monitoring programs has necessitated the reconstruction of past environmental conditions from proxy records of climate and geomorphology (e.g., Bluemle et al., 1999;Mann, 2002). For example, dendrochronology, and in some cases lichenometry, has been used to reconstruct local temperature and precipitation levels (e.g., Vogel et al., 2001;Cook et al., 2002), glacial fluctuations, debris flow, and snow-avalanche frequencies (McCarroll, 1993;Winchester and Harrison, 1994;Winchester and Chaujar, 2002) and to estimate the age of landforms and surface features (Winchester and Harrison, 2000;Bradwell, 2001). ...
Plant species with morphological features that enable the age of individuals to be estimated are potentially useful for understanding past environmental conditions. Here, the size and growth rate of the cushion plant, Azorella selago Hook. (Apiaceae), are examined to determine if an accurate and reliable age can be assigned to individual plants using the phytometric model detailed by Frenot et al. (1993). Plant size, growth rate, epiphyte load, nearest-neighbor characteristics, and spatial position (used as a surrogate, to encompass a range of abiotic conditions to which plants were exposed) were measured at three sites. Additionally, variation in some of these variables was quantified across three altitudinal transects. Relationships were examined using regression, trend surface and partial regression approaches. Growth rate was independent of plant size, differed between sites, and was related to abiotic as well as other biotic factors. As a result, the phytometric model's age estimates may be biased by environmental variables. The results of the phytometric model, albeit in the absence of support for one assumption, estimated mean plant age at 30 yr, with some plants estimated as older than 80 yr. Using a simulation model, the accuracy of age estimates was shown to vary with temporal variation in plant growth rate and plant size. Nonetheless, even a conservative approach suggested these estimates to be accurate to within 2 to 15 yr. While further development of the phytometric model would improve its reliability, the model remains a valuable tool for estimating plant ages in an environment where many related techniques can not be applied.
... Our results further confirmed the conclusions of the earlier studies that the major driver of DL flooding is regional climate variability (Bluemle et al., 1999;Kharel and Kirilenko, 2015;Vecchia, 2011). For example, in the absence of outlet operation and under the current climate the risk of DL overspill in the following 20 years is 81% and an increase of the wetland area to the historical estimates (scenarios 4 and 5) is only able to reduce this risk to 16-40% (Table 3). ...
Flood control is one of the most important ecosystem services provided by wetlands. Large-scale loss of wetlands, combined with more intensive precipitation under changing climate, increases flood risks, to which closed watersheds are particularly susceptible. In the Devils Lake (North Dakota, USA) watershed, a prolonged wet condition since early 1990s has caused a nearly 10 m rise in water level, resulting in over $1 billion losses. While studies have shown the changing climate is the major driver of this flooding, it is still unclear how much contribution could be due to the historical conversion of wetlands in the upper basin. We developed a Soil and Water Assessment Tool (SWAT) model for the Devils Lake watershed and simulated various scenarios representing present and possible past and future wetland area. We estimated the changes in flood risks under the historical and CMIP-5 future climates with these wetland scenarios. We found that while currently wetland restoration does not significantly change flood risks, under the modified climate it presents a good complementary measure reducing the negative impacts of current flood management strategies.
... Wibjörn Karlén has lately pursued his studies of the mechanisms behind natural climate variability (Karlén and Kuylenstierna 1996;Bluemle et al . 1999;Karlén 2001). For example, in a comparison of over 50 climate records, Mayewski et al . (2004) identified a number of rapid global climate events during the Holocene, which they suggested were primarily caused by changes in solar variability, thus confirming earlier results from the study of glacier variations (Denton and Karlén 1973a). ...
... 2 Background 2.1 Long-term hydroclimatic variation in the northern Great Plains Bluemle et al. (1999) reviewed the geological record of Devils Lake lake-level fluctuations during the late Holocene and concluded that the natural condition for the lake is to be either rising toward overflow to the neighboring Stump Lake or Sheyenne River, or falling toward desiccation as a dry lake bed. He concluded that the lake had dried up completely five or six times and overflowed past the ordinary high water mark at least twice in the last 4000 years. ...
Devils Lake, a terminal saline lake in eastern North Dakota, has experienced catastrophic flooding over the past two decades producing direct damages in excess of $1 billion ($USD). We use three long-term datasets to examine the temporal coherence between historical lake fluctuations and basic hydroclimatic drivers. Monthly precipitation and mean monthly air temperature data are used to characterize long-term precipitation delivery and evaporative demand. Monthly water balance data for a representative location are used to assess basin soil moisture conditions. A lake volume time series documents lake volume fluctuation in response to long-term precipitation and regional soil moisture conditions. Three variables are derived from the datasets, each characterizing a different aspect of the region’s hydroclimatology. A rescaling technique is applied to each variable to examine the temporal coherence and relative patterns of the variables and to identify distinct homogeneous hydroclimatic regimes during the historical period. The three rescaled variables show strong temporal coherence and confirm 1980 as an abrupt transition year between two distinct long-term hydroclimatic modes. Mode 1, a longer and drier phase, runs from 1907 to 1980, while mode 2, a shorter and wetter phase, extends from 1981 to the present. Multi-decadal and century-scale fluctuations between these two modes are the key drivers of long-term lake volume fluctuations, upon which interannual- and interdecadal-scale climatic variability are superimposed. The similar rates of change among the rescaled variables provides evidence in support of the conclusion that long-term natural hydroclimatological variability is the primary driver of observed lake volume changes at Devils Lake during the Twentieth Century and provides a foundation upon which to evaluate the potential contributing effects of anthropogenic climate change, and human alterations of the land use hydrology.
... Given that we know climate, and hence environmental conditions, have varied over a range of timescales from tens of millions of years to decades [Bluemle et al., 2001] and that rapid future climate change is likely [Karl and Trenberth, 2003], it is reasonable to infer a priori that groundwater recharge rate should be considered a transient rather than a constant flux. Temporal variations in recharge can have important consequences for the availability of groundwater resources and their management. ...
... WSE at Devils Lake has fluctuated between extremes of having gone completely dry to having spilled over to the Red River of the North multiple times over the past 4000 yr due to natural long-term climate fluctuations (Bluemle et al. 1999). Preliminary climatological investigations suggest that natural hydro-climatic variability is the most likely proxi-mate cause of the recent lake rise (Hoerling et al. 2010). ...
Since the spring of 1993, the water surface elevation at Devils Lake, a terminal lake in eastern North Dakota, USA, has risen by 8.8 m, producing more than 1 billion USD in direct flood damages. We examine the relationship between weather-type frequencies at Bismarck, North Dakota, and lake volume changes from 1965 to 2010 using the Spatial Synoptic Classification (SSC) system. First, we find statistically significant changes in the frequency of selected weather types over both annual and seasonal time periods. This indicates a trend toward in -creased advection of more humid weather types that is consistent with the historical rise in lake level. Second, a comparison of weather type frequencies between a subset of years with extreme large and small lake surges, and extreme large and small lake drawdowns, shows that weathertype frequency plays an important role in explaining annual lake volume fluctuations. The results support a climatic explanation for the historical lake rise at Devils Lake, but the relationships are not as strong as might have been anticipated given the unprecedented lake rise that occurred during the study period. A more detailed examination of the complex and non-linear nature of the lake water balance may be needed to further clarify how precipitation input is translated into lake volume changes.
... Because of increasing human fossil fuel use since the beginning of intensive industrial activity (Houghton, 1999), the world has experienced an increase in atmospheric CO 2 . It is widely believed that anthropogenic additions of CO 2 to the atmosphere are contributing to increase surface temperatures worldwide, a phenomenon known as the ''greenhouse effect'' (Bluemle et al., 1999). IPCC (2007) reports show that the global temperature increased approximately 0.3 °C per decade from 1979 to 2005. ...
Gradual increases in temperature and atmospheric CO 2 concentrations have resulted from the increased human use of fossil fuels since the beginning of industrial activity. In coastal wetland ecosystems, salt marshes constitute important habitats because they play important ecological roles, acting as carbon sinks by capturing atmospheric CO 2 and storing it in living plant tissue. Ecological models are important tools for understanding the results of anthropogenic impacts on a global scale. Global warming poses threats to salt marshes through different effects, e.g., increases in sea level. The objectives of this study were i) to assess how temperature increases will influence the growth of salt marsh plants, ii) to infer the carbon budget of salt marshes under temperature increase scenarios and iii) to predict how salt marsh plants will keep pace with increases in sea level. These goals were achieved by developing growth models of three different plants (Spartina maritima, Scirpus maritimus and Zostera noltei) found in the Mondego estuary. Models were developed for C 3 and C 4 plant species. The results suggest that a temperature increase enhances the aboveground biomass of salt marsh plants. According to the predictions of the models, the sedimentation rate of S. maritima and Z. noltei can keep pace with increases in sea level, but this is apparently not the case for S. maritimus. If S. maritimus disappears from the Mondego estuary, the carbon sequestration ability of the system should decrease due to the loss of active plant tissue. This conclusion is based on the fact that S. maritimus accumulated more than 80% of the total carbon sequestered in the tissues by the three studied species.
... T he most recent report of the Intergovernmental Panel on Climate Change (IPCC) indicates that the average global temperature will probably rise between 1.1 and 6.4°C by 2090-2099, as compared to 1980-1999 temperatures, with the most likely rise being between 1.8 and 4.0°C (IPCC, 2007a). The idea that the Earth's climate is changing is now almost universally accepted in the scientifi c community (Cooney, 2010;Corfee-Morlot et al., 2007), and even many scientists who dispute that climate change is anthropogenic are in agreement that it is happening (i.e., Kutílek, 2011;Carter, 2007;Bluemle et al., 1999). Therefore, even if we can't agree on why climate change is happening, it should be possible to agree that it is happening, and with climate change happening, there will be eff ects on the environment, including the soil. ...
According to the Intergovernmental Panel on Climate Change, global temperatures are expected to increase 1.1 to 6.4 OC during the 21st century and precipitation patterns will be altered by climate change. Soils are intricately linked to the atmospheric/climate system through the carbon, nitrogen, and hydrologic cycles. Altered climate will, therefore, have an effect on soil processes and properties and at the same time the soils themselves will have an effect on climate. Studies into the effects of climate change on soil processes and properties are still incomplete, but have revealed that climate change will impact soil organic matter dynamics including soil organisms and the multiple soil properties that are tied to organic matter, soil water, and soil erosion. The exact direction and magnitude of those impacts will be dependent on the amount of change in atmospheric gases, temperature, and precipitation amounts and patterns. Recent studies give reason to believe at least some soils may become net sources of atmospheric carbon as temperatures rise; this is particularly true of high latitude regions with permanently frozen soils. Soil erosion by both wind and water is also likely to increase. However, there are still many things we need to know more about. How climate change will affect the nitrogen cycle and, in turn, how the nitrogen cycle will affect carbon sequestration in soils is a major research need, as is a better understanding of soil water-CO2 level-temperature relationships. Knowledge of the response of plants to elevated atmospheric CO2 given limitations in nutrients like nitrogen and phosphorus and how that affects soil organic matter dynamics is a critical need. There is also a great need for a better understanding of how soil organisms will respond to climate change because those organisms are incredibly important in a number of soil processes, including the carbon and nitrogen cycles.
... Global average surface temperature has increased by approximately 0.6-0.8uC during the last century [1,2]. Average maximum temperature (during the period 1950-2000) for Sikkim, as interpolated from Worldclim data [3], is 8.1uC, varying from 210.9uC to 28uC (68.3uC). ...
Export Date: 26 November 2013, Source: Scopus, Art. No.: e57103
... The authors conclude that the Gulf of Mexico microtidal barrier islands record architectural evidence of multiple ultra-high-frequency sealevel cycles, of approximately 400 to 500 years duration, during the latest Holocene. Climate-induced, geological and base-level cycles of 400 to 500 years have also been reported by other researchers (e.g., Skilbeck et al. 2005;Bluemle et al. 2001;Chapman and Shackleton 2000;Wanner et al. 2008). The climate changes inferred from the Padre Island GPR study, manifest as sea-level rises accompanied by possible increases in storm intensity, as indicated by washover-channel scour depth, are consistent with the 550 year cyclicity driven by changes in North Atlantic Deep Water (NADW) circulation patterns (e.g., Chapman and Shackleton 2000) and/or the atmospheric North Atlantic Oscillation (NAO) (e.g., Holzhauser et al. 2005). ...
Padre Island is the widest and longest barrier island in the world. It is 200 km long, up to 3 km wide, and 10-15 m thick. This 2,000-year-old barrier island was formed predominantly from northward longshore-drifted sediments from the Rio Grande River Delta. A 3-km-long, shore-normal, 50 MHz ground-penetrating radar (GPR) profile was collected across Padre Island from the Gulf of Mexico to Laguna Madre at the northern end of the Padre Island National Seashore. A 1-km-long, shore-parallel GPR profile was also collected and intersects the shore-parallel profile approximately 1 km landward of the Gulf of Mexico. Vibracores taken along the shore-normal profile, at the beach foreshore, in the center of the island, at the lagoon margin, and at a recent washover fan were used, in conjunction with the description of a deep rotary core taken through the northern part of the island, to constrain the GPR interpretations. In the shore-normal profile, GPR reflectors indicate both seaward- and landward-dipping clinoforms, as well as concave-upward scour-and-fill features. Seaward-dipping reflectors indicate approximately 2 km of progradation of the barrier island, suggesting an average progradation rate of 1 m/year. Landward-dipping reflectors, in the landward 1 km of the GPR profile, indicate approximately 1 km of landward growth, suggesting an average landward growth rate of 0.5 m/year. Nested concave-upward scour-and-fill features in the central part of the island are interpreted as tidal and washover channels 3-8 m deep. In strike cross section these scours are channel-form in outline and contain nearly horizontal, to slightly inclined, radar reflectors. The presence of channel-form scours supports the interpretation that landward growth was dominantly due to deposition by short-lived tidal deltas and storm washovers. Even though there was periodic landward island growth, North Padre Island has been progradational throughout its history due to a high sediment supply. The understanding of the architecture and growth history of Padre Island provides much needed information about the internal geometry and the evolution of modern barrier-island systems. In addition, systematic variations in scour depths across the island suggest that storm frequency and intensity varied during the island's history and provides a proxy for estimating sea-level fluctuations.
... The Greenland ice sheet project II has allowed Bluemle (2001) to characterize the Holocene as a sequence of ten or more global scale "little ice ages" fairly irregularly spaced, each lasting a few centuries. The cooling events occurred at 6600-6200 B.P., 4800-4300 B.P., 3000-2000 P.B., and the last 500 years (except for the past 100 years) (Fig. 44). ...
The complete meltdown of the Greenland and Antarctic ice sheets would raise the sea level 65 meters, whereas a partial meltdown only a few tens of meters. Eustatic sea level rates of changes in Greenland since 2003 show a net ice mass reduction of 96 gigatons per year; with this, geologists are called upon to add a historical perspective upon these changes.
Pre-Neogene continental rearrangements occurred at numerous episodes, masking the net effects of eustatic level fluctuations. Glacial advance is prominent during late Precambrian, late Carboniferous and Pleistocene. Greenhouse events and temperature increases are evident during the Devonian and Cretaceous. Paleo-continental landmass positions reveal a direct relationship to icehouse and greenhouse events. The restriction of global oceanic circulation at the equator brings about icehouse events. Absolute rates of change for comparison purposes to the present are currently impossible due to the multivariate effects (1) tectonic plate motion world wide; (2) variations in sedimentary processes; (3) diagenetic change in sedimentary rock; (4) subsidence, on the resultant stratigraphic record.
Since carbonate reefs reach the top of the subsea or photic zone, carbonate reef growth is an ideal indicator of sea level change. Carbonate deposits at the Caribbean — South America plate boundary are a prime example that plate motion can greatly supersede sea level fluctuations. The best areas to use carbonate reef data is along the Florida-Bahamas-Caribbean passive margins of the Atlantic basin, where Neogene tectonics and carbonate deposition were stable. The carbon dioxide levels were much greater above the K/T boundary, creating an environment devoid of significant carbonate buildups. The earliest significant quantitative sea-level rate of change data is derived from wells drilled into stable carbonate platforms of the late Neogene 2–7 Ma, when carbon dioxide levels decreased in the atmosphere. Cores show rates of paleo sea level rise averaging 10 to 20 cm/100yr versus currently between 17–32cm/100yr. The rate increase has nearly doubled within the past 14 years. This increased rate of change in sea-level has been recently highlighted at the 2007 Intergovernmental Panel on Climate Change in Paris, France.
In the past, rapid warming caused extreme increase in eustatic sea level rates of change reflected in geochemical data from carbonate Holocene reef cores from the west side of Barbados Island, drowned reefs off the, Florida coast, and from Bermuda. The measuring sea level changes of 1–2m/100yr are evident from 13,000–17,000 years ago. The warming is attributed to solar irradiance at glacial maximum during the Wisconsinan 14,000–20,000 years before present when sea level was as much as −175 meters lower than today. This lowered sea level evidence is derived from Holocene reefs south of the Great Barrier Reef in Australia. Bluemle (2001) characterizes the Holocene as a sequence of ten or more global scale “little ice ages” fairly irregularly spaced, each lasting a few centuries and separated by global warming events shown from the ice core data. Friedman (2005) noted an overall cooling trend in ocean waters based on Red Sea beach rock geochemical data from 7,000 to 2,000 years ago. Through all the erratic temperature swings over the past 4,000 years geochemical data from Holocene reef cores from Florida show a sea level rise of 12cm/100yr., typical of stable geological and climatological periods.
The Questions remains: Is the current rate change of sea level significant or, just another unanswered anomaly from the cycle curve?
... Global average surface temperature has increased by approximately 0.6-0.8uC during the last century [1,2]. Average maximum temperature (during the period 1950-2000) for Sikkim, as interpolated from Worldclim data [3], is 8.1uC, varying from 210.9uC to 28uC (68.3uC). ...
... In this introduction we provide a brief overview of the history of paleoclimatological studies in the Maya area. We show that the exigencies under which the Maya civilization developed and ultimately failed in the ninth century were a phenomenon of global perspective (Bluemle et al. 1999;Folan, Gunn, Eaton, and Patch 1983). ...
The series of papers on climate change published in this issue are the result of the symposium "Environmental Change in Mesoamerica: Physical Forces and Cultural Paradigms in the Preclassic to Postclassic," held at the 63rd Annual Meeting of the Society for American Archaeology in March 2000 in Philadelphia. The authors bring their expertise in paleoclimatological studies to hear on the Maya Lowlands and Highlands from the beginning of the Holocene to the Postclassic and modern times. The studies reveal that climate has changed during the past 4,000 years to a considerable degree that correlates in a reasonable way with archaeological periodizations. Several climate-change models are presented as an effort to understand better past cultural and natural events.
... In the last 250 years, industrial activity has increased with a concomitant increase of the fossil fuel usage (Houghton, 1999) and consequent atmospheric CO 2 increase. This has recognized consequences on climate change, namely increasing the global surface temperature (Bluemle et al., 1999; IPCC, 2007). As a way to mitigate the high concentration of CO 2 in the atmosphere it is important to look to plant ecosystems (for e.g. ...
... Global average surface temperature has increased by approximately 0.6-0.8uC during the last century [1,2]. Average maximum temperature (during the period 1950-2000) for Sikkim, as interpolated from Worldclim data [3], is 8.1uC, varying from 210.9uC to 28uC (68.3uC). ...
Global average temperature increase during the last century has induced species geographic range shifts and extinctions. Montane floras, in particular, are highly sensitive to climate change and mountains serve as suitable observation sites for tracing climate-induced biological response. The Himalaya constitute an important global biodiversity hotspot, yet studies on species' response to climate change from this region are lacking. Here we use historical (1849-50) and the recent (2007-2010) data on temperature and endemic species' elevational ranges to perform a correlative study in the two alpine valleys of Sikkim. We show that the ongoing warming in the alpine Sikkim Himalaya has transformed the plant assemblages. This study lends support to the hypothesis that changing climate is causing species distribution changes. We provide first evidence of warmer winters in the region compared to the last two centuries, with mean temperatures of the warmest and the coldest months may have increased by 0.76±0.25°C and 3.65±2°C, respectively. Warming-driven geographical range shifts were recorded in 87% of 124 endemic plant species studied in the region; upper range extensions of species have resulted in increased species richness in the upper alpine zone, compared to the 19(th) century. We recorded a shift of 23-998 m in species' upper elevation limit and a mean upward displacement rate of 27.53±22.04 m/decade in the present study. We infer that the present-day plant assemblages and community structure in the Himalaya is substantially different from the last century and is, therefore, in a state of flux under the impact of warming. The continued trend of warming is likely to result in ongoing elevational range contractions and eventually, species extinctions, particularly at mountaintops.
... In this introduction we provide a brief overview of the history of paleoclimatological studies in the Maya area. We show that the exigencies under which the Maya civilization developed and ultimately failed in the ninth century were a phenomenon of global perspective (Bluemle et al. 1999;Folan, Gunn, Eaton, and Patch 1983). ...
The series of papers on climate change published in this issue
are the result of the symposium “Environmental Change
in Mesoamerica: Physical Forces and Cultural Paradigms in the
Preclassic to Postclassic,” held at the 63rd Annual Meeting
of the Society for American Archaeology in March 2000 in
Philadelphia. The authors bring their expertise in
paleoclimatological studies to bear on the Maya Lowlands and
Highlands from the beginning of the Holocene to the Postclassic
and modern times. The studies reveal that climate has changed
during the past 4,000 years to a considerable degree that
correlates in a reasonable way with archaeological periodizations.
Several climate-change models are presented as an effort to
understand better past cultural and natural events.
... Attempts to explain why deep-water coral isolates from geographically different regions appear closely related have been hampered by a lack of knowledge of transmission of larvae from one host to another. We propose, although speculative, that the isolation of distinct DWC genes, and different clades and subclades as described by Berntson et al. (2001), is the result of shifting oceanic circulation (Benzie 1999) and global warming and cooling trends (Bluemle et al. 1999), where larval transmission is related to changing environments and host-specific signals. During periods of low sea levels and colder water temperatures, geographical barriers may have promoted coevolution of various DWCs to produce one or more dominant clades per geographical location. ...
Many deep-water coral species have very broad global distributions and are eurybathic from depths of meters to kilometers.
Such ecological breadth may be confounded by the presence of cryptic species. We are currently comparing the genetic distances
between Paragorgia sp. and Primnoa sp. across their distribution and depth range in Canada using 18S ribosomal DNA (rDNA) sequences. Initial results show a
confusing picture amongst the geographically distant Paragorgia taxa. Specimens of P. arborea from the Canadian Atlantic are very divergent from the specimen from the Canadian Pacific. The placement of Pennatula and Anthomastus relative to these taxa is also unexpected. We expect this topology to alter with the addition of more taxa and further testing.
... Temperatures during the Hypsithermal (4,000-8,000 years B.P.) in the northern Central Plains were 1 • C to 2 • C ( Bartlein et al. 1984Bartlein et al. , 1998 or 2 • C to 3 • C (Denton and Porter 1970) warmer than today. Bluemle et al. (1999) characterized this period as ten or more "little ice ages" separated by global warming events. Records during this period showed evidence of aridity, increased salinity, and higher than present temperatures, with grasslands spreading farther north (Lemmen et al. 1997). ...
The Prairie Pothole Region (PPR) is unique to North America. Its millions of wetlands and abundant ecosystem goods and services
are highly sensitive to wide variations of temperature and precipitation in time and space characteristic of a strongly continental
climate. Precipitation and temperature gradients across the PPR are orthogonal to each other. Precipitation nearly triples
from west to east from approximately 300mm/year to 900mm/year, while mean annual temperature ranges from approximately 1°C
in the north to nearly 10°C in the south. Twentieth-century weather records for 18 PPR weather stations representing 6 ecoregions
revealed several trends. The climate generally has been getting warmer and wetter and the diurnal temperature range has decreased.
Minimum daily temperatures warmed by 1.0°C, while maximum daily temperatures cooled by 0.15°C. Minimum temperature warmed
more in winter than in summer, while maximum temperature cooled in summer and warmed in winter. Average annual precipitation
increased by 49mm or 9%. Palmer Drought Severity Index (PDSI) trends reflected increasing moisture availability for most
weather stations; however, several stations in the western Canadian Prairies recorded effectively drier conditions. The east-west
moisture gradient steepened during the twentieth century with stations in the west becoming drier and stations in the east
becoming wetter. If the moisture gradient continues to steepen, the area of productive wetland ecosystems will shrink. Consequences
for wetlands would be especially severe if the future climate does not provide supplemental moisture to offset higher evaporative
demand.
... The current global warming event is comparable to past episodes of glacial retreat [11]. Specifically, the rate of air temperature increase in the early Holocene and the concomitant deglaciation are thought to be similar to current trends on the 100year scale [12,13]. Given these similarities, a productive natural experiment for exploring the genetic consequences of rapid colonization after a global warming event is to survey the current genetic makeup of populations that have undergone a rapid expansion following the retreat of glacial ice sheets 10,000 to 12,000 years ago [14,15]. ...
Global climate change is expected to trigger northward shifts in the ranges of natural populations of plants and animals, with subsequent effects on intraspecific genetic diversity. Investigating how genetic diversity is patterned among populations that arose following the last Ice Age is a promising method for understanding the potential future effects of climate change. Theoretical and empirical work has suggested that overall genetic diversity can decrease in colonial populations following rapid expansion into postglacial landscapes, with potential negative effects on the ability of populations to adapt to new environmental regimes. The crucial measure of this genetic variation and a population's overall adaptability is the heritable variation in phenotypic traits, as it is this variation that mediates the rate and direction of a population's multigenerational response to selection. Using two large full-sib quantitative genetic studies (N(Manitoba) = 144; N(South Dakota) = 653) and a smaller phenotypic analysis from Kansas (N(Kansas) = 44), we compared mean levels of pigmentation, genetic variation and heritability in three pigmentation traits among populations of the common garter snake, Thamnophis sirtalis, along a north-south gradient, including a postglacial northern population and a putative southern refuge population. Counter to our expectations, we found that genetic variance and heritability for the three pigmentation traits were the same or higher in the postglacial population than in the southern population.
... This disregard can be attributed to some degree due to the lack of awareness among the general population in terms of causes and potential effects of climate change within the world's environment (Dessler, & Parson, 2006). There previously has been some opposition to the existence of human caused climate change and resulting global warming as a threat to the earth's population and survival, however, scientific evidence has more recently been found to be compelling (Bluemle, Sabel, Sabel, & Karlen, 1999;Claussen, Cochran, & Davis, 2001;Dow & Downing, 2006;Christianson, 1999;Crutzen, & Graedel, 1997;IPCC, 1990IPCC, , 1992IPCC, ,1996IPCC, , 2001IPCC, , 2007Goudie & Cuff, 2002;Houghton, 2004;McCaffrey, 2006;Naomi, 2004; National Academy of Sciences Committee on the Science of Climate Change, 2001;O'Hare, Sweeney, & Wilby, 2005;Weart, 2003). ...
Climate change and potential global warming has become important in many forums both nationally and internationally. Though there has previously been some opposition to the existence of human caused climate change and resulting global warming as a threat to the earth’s population and survival, scientific evidence has more recently been found to be compelling. One of the key industries that may be affected by global warming and climate change is the tourism industry. This is becoming a growing concern in Florida, U.S.A. where potential rising sea levels may have a profound effect. This paper discusses the development, importance and implications of climate change, its relationship to the tourism and hospitality industry and provides a case study of the Florida lodging industry regarding mechanisms and responses that the lodging and resort sector of the industry has been taking in addressing climate change factors.
... Climate: The average statistics (mean, variability, even extremes) of the meteorological conditions, including temperature, precipitation and wind, that characteristically prevail in a particular region. Climate has always been changing or, more precisely, been varying, independently of the time scale of the observer, including geological time scales (Bennett 1997; Bluemle et al. 2001). It should be noted that we can, and should, separate between climatic change, which is the change (a trend) of the climate over a longer time period, at least 20 years, and climatic variability, which describes the variation of the climate, for example year-to-year oscillations. ...
Added thesis t.p. tipped in. Thesis (Ph. D.)--Uppsala University, 2001. Includes bibliographical references (p. 31-37).
... Many scientists, as well as the public sector, now believe that anthropogenic additions of CO 2 to the atmosphere are contributing to a rise in global mean surface temperatures, a phenomenon known as the ''greenhouse effect'' (Mosier, 1998;Bluemle et al., 1999). The realization that increasing the organic matter content of soils can effectively remove CO 2 from the atmosphere has made carbon sequestration an important research topic in soil science in recent years (Hakamata et al., 1997;Paustian et al., 1997;Batjes, 1998;Lal et al., 1998b;Mosier, 1998). ...
Soils on the Mormon Trail have been compacted for over 150 years. Bulk density, carbon, and nitrogen samples were taken in 5-cm increments to 20 cm. Bulk density was determined using rings of known volume; total carbon and nitrogen with a LECO CHN-600. Total above ground biomass (AGB) samples were collected by clipping vegetation within a 0.25 m2 frame and were analyzed for carbon. Statistical comparisons were made using a t-test (alpha = 0.05). Bulk density was higher in the on-trail soils from 5 to 20 cm; soil carbon and C/N ratios were higher in the off-trail soils from 10 to 20 cm. AGB and AGB carbon is significantly less on the trail. Results indicate the compacted layer on the trail alters the soil carbon pool by limiting additions of fresh organic matter to the soil, limiting vegetative production, and by "pooling" carbon additions in the upper 10 cm of the soil.
Proxy variables from palaeolimnological studies of lakes in the Prairie Pothole Region of North America have been used to infer large oscillations during the late Holocene between longer periods of high-salinity–dry conditions and shorter periods of low-salinity–wet conditions producing a normative pattern marked by the absence of hydrological stability. Studies of the historical rise in lake level at Devils Lake have identified 1980 as a transition point between two such hydroclimatic modes. This study uses multiple datasets to characterize the mean hydroclimatological and hydrological conditions of these two climatic modes. Mode 1 is a cool and dry phase, and mode 2 is a warmer and wetter phase. Precipitation onto the lake increased by 24% from mode 1 to mode 2. This small, but sustained, increase produced significant changes in the mean hydroclimatic and hydrological states for the basin, including a 383% increase in surface run-off to the lake, and a 282% increase in the basin run-off ratio. Devils Lake Basin is located along a hydrotone (region of strong hydroclimatic gradients) where small changes in hydrological drivers are amplified into large changes in regional moisture. The effects of the fluctuating climatic modes and strong hydroclimatic gradients are probably further amplified by the unique fill–spill hydrology of the northern glaciated plains, which can result in nonlinear precipitation–run-off relationships. This natural pattern of extreme hydrological variations for Devils Lake produces enormous challenges for lake management.
Economic planning is basically the responsibility of the government but the private sector also has to contribute through informed policy inputs and implementation strategies. Private sector plays pivotal role in the growth process of an economy. The large as well as the SMEs not only provides employments to labors force but also uses state of the art technologies to produce goods and services for domestic as well as international consumers. Doing business by Government is just as disastrous as government oppression. Pakistan is witnessing the inefficiencies, overstaffing and tremendous financial losses in few enterprises run by Government. These become liabilities and in order to run these Governments is bearing millions of rupees as “bailout packages”. The present PML-N government realized the important of privatization and intends to privatize number of Government run enterprises. The paper highlights the role of private sector in business and government role as providing conducive growth strategies & governance. The overtime historical policy analysis, constraints to private sector development and strategies to overcome these will be explored. The papers further emphasize the role and significance of 3Ps projects, their risks and ways to successfully implementation of them.
The AAPG Ad Hoc Committee on Global Climate Issues has studied the supposition of human-induced climate change since the committee's inception in January 1998. This paper details the progress and findings of the committee through June 1999. At that time there had been essentially no geologic input into the global climate change debate. The following statements reflect the current state of climate knowledge from the geologic perspective as interpreted by the majority of the committee membership. The committee recognizes that new data could change its conclusions. The earth's climate is constantly changing owing to natural variability in earth processes. Natural climate variability over recent geological time is greater than reasonable estimates of potential human-induced greenhouse gas changes. Because no tool is available to test the supposition of human-induced climate change and the range of natural variability is so great, there is no discernible human influence on global climate at this time.
Salt marshes have great ecological value for the ecosystem, namely in nutrient regeneration, primary production, habitat for wildlife species and as shoreline stabilizers. Their important role has been recently admitted by the inclusion of these ecosystems in the Water Framework Directive (WFD). Multiple services of wetlands and value are already well known. As it is now known the major carbon sink of the planet are the oceans (38 630 Pg C), followed by the terrestrial zones. Considering the terrestrial sink (1 400 Pg C), the more productive and more important zones retaining carbon are the wetlands retaining about 1/2 to 1/3 of the carbon (455-700 Pg C). Vascular plants in salt marshes are crucial to the dynamics of the estuarine ecosystem, strongly influencing the processes of retention of heavy metals, reduction of eutrophication and mitigation of carbon. Salt marsh plants (halophytes) are characterized by, among other, being extremely productive. Their product is directly linked to the important role they play in estuaries, in terms of the value-added. The evident zonation in salt marsh vegetation is now accepted as result of competitive advantages of superior plants to colonize particular habitats with more favorable physic-chemical characteristics, leading to the drawback of less competitive species. External stresses driven by warming, like nutrient imbalances (similar to eutrophication), may lead to the success of less competitive species, through belowground competition alleviation. CO2 can be another key factor altering plant dynamics, favoring species with higher aerial biomass production and increasing competition for light. These differences in plant biomass allocation are also to be considered in terms of plant dominance as an important part of interspecific competition. With CO2 increase, the dynamics of plant distribution may be affected, as the differences in the photosynthetic metabolisms will provide some species conditions of higher production, and therefore competitive advantage. How CO2 will affect these important salt marsh areas, is one of the important questions addressed in the present chapter. The opposite point of view is also important to be accounted for; how can salt marshes contribute to reducing CO2? And more important from the holistic point of view; how will these changes affect the services provided to the ecosystem? Therefore integrating the fact that these ecosystems are very productive with the generally accepted knowledge that global atmospheric CO2 is rising, becomes important to know the present status of salt marsh systems and how their important services to the ecosystem will behave in a climate change scenario of increasing atmospheric [CO2]. The present chapter intends to address this subject from several points of view, using a multi-disciplinary approach including microbiology, plant physiology, stable isotope discrimination and ecological modeling.
Keeping in view the poor efficiency of Pakistan‘s irrigation
system at 40 per cent the need is truly crucial for adapting
water management practices to improve water availability and
productivity at the farm. These practices include mainly
watercourse improvement, precision land levelling, bed
planting, and high efficiency irrigation systems, which have
the potential to save water in the range of 20 to 70 per cent,
increase crop yields by 20 to 30 per cent and increase farmers‘
net income by 20 per cent. Whereas drip irrigation coupled
with balanced fertigation has huge potential of bringing
improvement in the livelihood of farmers, especially if they
switch to high value crops, in general the success of these
practices would depend on creating awareness among farmers,
providing them backup support and at-field intensive training..
Besides these issues, Pakistan is the state most vulnerable to
climate change facing glacier retreats, floods, droughts and
projected rise in temperature of 2ºC by 2050. Moreover,
climate change can reduce rice yields from 8 to 30 per cent
and wheat yields from 6 to 19 per cent, increasing poverty
levels to 6 per cent by 2050.
Valdosta State University owns property that includes a borrow pit excavated in 1961 to supply sand as fill during construction of Interstate Highway 75. This pit has revegetated naturally with no remediation, allowing investigation of natural rates of C sequestration in the pit over the last ~ 40 yr. Three distinct areas have been identified in the pit based on vegetation: an area of mixed deciduous and pine trees in the deepest part of the pit, a sparsely vegetated area on the edge of a terrace within the pit, and an area with grass and mixed deciduous and pine trees. Soils (Albany series, Loamy, siliceous, subactive, thermic Grossarenic Paleudults) outside the pit were also sampled as a control. Total soil C was measured and bulk density (g cm-3) was determined. Mass of soil C in the upper meter of the profile was determined (total soil carbon * bulk density). Total profile soil carbon values averaged 2.2 kg C m-2 in the deep pit, 0.4 kg C m-2 in the sparsely vegetated area, 3.6 kg C m-2 in the grassy area, and 5.9 kg C m-2 in the control. Piezometers indicate water is often close to or above the surface in the deep pit and grassy areas and >2-m deep in the sparsely vegetated area. Carbon sequestration rates are controlled by vegetative type and density which, in turn, appear to be controlled by soil bulk density, availability of soil water, and probably soil nutrient content (not measured).
Although a considerable increase in our knowledge concerning the importance of metabolic adjustments to unfavourable growth conditions has been recently provided, relatively little is known about the adjustments which occur in response to fluctuation in environmental factors. Evaluating the metabolic adjustments occuring under changing environmental conditions thus offers a good opportunity to increase our current understanding of the crosstalk between the major pathways which are affected by such conditions. To this end, plants growing under normal conditions were transferred to different light and temperature conditions which were anticipated to effect (amongst other processes), the rates of photosynthesis and photorespiration and characterized at the physiological, molecular and metabolic levels following this transition. Our results revealed similar behaviour in response to both treatments and imply a tight connectivity of photorespiration with the major pathways of plant metabolism. They further highlight that the majority of the regulation of these pathways is not mediated at the level of transcription but that leaf metabolism is rather pre-poised to adapt to changes in these input parameters.
According to the Intergovernmental Panel on Climate Change, global temperatures are expected to increase 1.1 to 6.4 degrees C during the 21st century and precipitation patterns will be altered by climate change (IPCC, 2007). Soils are intricately linked to the atmospheric/climate system through the carbon, nitrogen, and hydrologic cycles. Altered climate will, therefore, have an effect on soil processes and properties. Studies into the effects of climate change on soil processes and properties are still incomplete, but have revealed that climate change will impact soil organic matter dynamics including soil organisms and the multiple soil properties that are tied to organic matter, soil water, and soil erosion. The exact direction and magnitude of those impacts will be dependent on the amount of change in atmospheric gases, temperature, and precipitation amounts and patterns. Recent studies give reason to believe at least some soils may become net sources of atmospheric carbon as temperatures rise; this is particularly true of high latitude regions with permanently frozen soils. Soil erosion by both wind and water is also likely to increase. These soil changes will lead to both direct and indirect impacts on human health. Possible indirect impacts include temperature extremes, food safety and air quality issues, increased and/or expanded disease incidences, and occupational health issues. Potential direct impacts include decreased food security and increased atmospheric dust levels. However, there are still many things we need to know more about. How climate change will affect the nitrogen cycle and, in turn, how the nitrogen cycle will affect carbon sequestration in soils is a major research need, as is a better understanding of soil water-CO2 level-temperature relationships.
Knowledge of the response of plants to elevated atmospheric CO2 given limitations in nutrients like nitrogen and phosphorus and how that affects soil organic matter dynamics is a critical need. There is also a great need for a better understanding of how soil organisms will respond to climate change because those organisms are incredibly important in a number of soil processes, including the carbon and nitrogen cycles. All of these questions are important in trying to understand human health impacts. More information on climate change, soils, and human health issues can be found in Brevik (2012).
Wetland ecosystem occupies an important position in the global carbon cycle with a strong ability of carbon storage and fixation. On the basis of field investigation and laboratory measurement, in the paper, the standing biomass and primary production of wetland Phragmites australis in Baiyangdian were study, and its ability of carbon storage and fixation in accordance with the principle of photosynthesis was measured, and then the potential ability of carbon storage from the perspective of efficiency for solar energy utilization was discussed. The results show that carbon storage of wetland Phragmites australis is large in Baiyangdian with 5.81 kg • m-2, 7.14 kg • m-2 and 8.72 kg • m-2 respectively; carbon fixation is also very large with 2.54 kg • m-2, 3.12 kg • m-2 and 3.81 kg • m-2 respectively. In addition, the underground biomass is larger than the aboveground biomass, and the ratio of the two is 2.38-3.30 with the average of 2.90. The underground carbon storage is nearly 3 times as much as the aboveground carbon storage. Wetland Phragmites australis in Baiyangdian has a strong ability of carbon fixation with 1.17 kg • m-2 • a-1, 1.49 kg • m-2 • a-1 and 1.76 kg • m-2 • a-1 respectively, which is 1.7-3.4 times as much as the average ability of carbon fixation of the national terrestrial plants and 2.0- 4.0 times of that of the global plants.
The global drivers that determine the Earth's climate are: (1) solar radiation as a dominant energy supplier to the earth, (2) the Earth's outgassing as a major supplier of gasses to the hydrosphere and atmosphere, and, (3) possibly microbial activities generating and consuming atmospheric gases at the interface of lithosphere and atmosphere. The authors provide quantitative estimates of the scope and extent of their effects on the Earth's climate. Comparison of these estimates with the corresponding anthropogenic effects shows that the human-induced climatic changes are negligible with respect to global forces of nature. One should not ignore the fact that peaks in solar irradiation precede peaks in CO2 concentration. Using the adiabatic model developed by the famous Russian Scientist, Dr. O.G. Sorokhtin, the authors show that the increase in CO2 concentration in atmosphere will result in cooling rather than warming. Thus, the attempts to alter the global climatic changes (and drastic measures prescribed by the Kyoto protocol) have to be abandoned as meaningless and harmful.
Commonly called "bubblegum coral', Paragorgia is a genus of cold-water gorgonian coral that has a broad global distribution and is eurybathic from depths of meters to kilometers. Such ecological breadth, however, may be confounded by the presence of cryptic species. In this study the genetic distances of various Paragorgia spp. across their distribution and depth range along the Canadian mid-Atlantic margin using 18S ribosomal DNA sequences were compared. Morphometric and 18S evidence show that although appearing closely related, only one species of cold-water Paragorgia, called P. arborea, predominates in this region. However, 18S evidence from corals collected at deep depths located at one site, called the Stone Fence, indicate that a significant amount of divergence exists and other species may also be present. Such new light provides a need for further genetic testing using alternative methods (e.g. microsatellites), which could reveal new lineages that may have considerable ecological and/or taxonomic importance.
The authors identify and describe the following global forces of nature driving the Earth’s climate: (1) solar radiation as a dominant external energy supplier to the Earth, (2) outgassing as a major supplier of gases to the World Ocean and the atmosphere, and, possibly, (3) microbial activities generating and consuming atmospheric gases at the interface of lithosphere and atmosphere. The writers provide quantitative estimates of the scope and extent of their corresponding effects on the Earth’s climate. Quantitative comparison of the scope and extent of the forces of nature and anthropogenic influences on the Earth’s climate is especially important at the time of broad-scale public debates on current global warming. The writers show that the human-induced climatic changes are negligible.
Climatic variation and change affect the dynamics of organisms and ecosystem processes. Many studies in the past have analyzed and discussed various climate-driven effects on different components of the lake ecosystem. Only a few synthesis papers have been published in this field. In this overview, a conceptual model has been developed to help explain why lakes respond individually to climate. The model consists of two main components, a so-called Landscape Filter comprising the features of geographical position, catchment characteristics and lake morphology, and a so-called Internal Lake Filter, comprising the features of lake history and biotic/abiotic interactions. The application of this conceptual model on published literature findings illustrates the strength in this encompassing perspective. An assessment of current climate research methods is presented with some perspectives given.
The stable isotope composition of organic carbon (OC), abundance of OC and nitrogen, and C/N ratios for core T97-69V are used
to document late Holocene variability in the sources of organic matter (OM) in the Malagarasi delta (Lake Tanganyika) and
in precipitation in the Malagarasi catchment basin. Core T97-69V, located at latitude 5°12.92′S and longitude 29°40.50′E,
was retrieved at a water depth of 60 m. The organic δ13C values for this core ranges from −25.0λ to −19.8λ and averages −23.0∀λ. The δ13C values decrease down-core to the base of the core with one spike of depleted δ13C values interrupting this general trend. A similar trend of down-core decrease is also observable for the contents of OC
and nitrogen whose abundance averages 3.75∀1.1% and 0.4∀0.1% respectively. In contrast, the C/N ratios with mean value of
11∀2.3 do not display any clear down-core trend. Furthermore, there is a sharp shift in the stable isotope compositions of
OC to lower values at about 200 cm. An enrichment in 13C in the upper 200 cm associated with higher contents of OC and nitrogen and relatively low C/N ratio values can probably
be attributed to complete utilisation of available nutrients (high primary productivity) in conjunction with deposition of
large proportion of C4 material derived from the catchment areas. Low isotope values of up to 4λin the lower 200 cm of the core suggest higher input
of C3 type of material derived from phytoplankton and terrestrial plants. Furthermore, a downcore decrease in 13C suggests that the level of precipitation in the Malagarasi Basin has decreased since mid-Holocene, and most likely this
trend was associated with a decrease in the lake levels. Two spikes of low isotope values may suggest period of above normal
precipitation that resulted into transportation of a significant quantity of terrestrial OM.
Coastal wetlands have the potential to accumulate C at high rates over long time periods because they continuously accrete and bury organic-rich sediments, giving soils in coastal wetlands a distinct advantage over many other environments in the sequestration of organic C. Given that coastal wetlands are being lost worldwide, it is important to understand their C sequestration potential. Sediments in a southern California, USA coastal lagoon–wetland complex were cored, and depositional environments were interpreted. Suitable materials were radiocarbon dated. Bulk density and organic C were grouped by depositional environments, and average mass of C per unit volume and C accumulation rates in each depositional environment were calculated. The total organic C sequestered and rates of sequestration in each depositional environment were in the following order from most (fastest) to least (slowest): lagoon, intertidal, salt marsh, freshwater marsh, aeolian. This study demonstrated that high levels of organic C are sequestered per unit volume of sediment (35.9±3.2 kg m−3), and the mean rate of C accumulation was high (0.033±0.0029 kg C m−2 year−1) over a long time period (5000 years). Results of this study strongly demonstrate the importance and necessary high priority for preserving and restoring coastal wetlands both in the USA and internationally. However, despite their excellent potential to sequester C, significant losses of coastal wetlands are occurring in the United States and elsewhere in the world.
Remains of true bugs (Heteroptera) and beetles (Coleoptera) from archaeological occupation deposits of the past two millennia appear to provide evidence that temperatures in northern England in the 1st 4th and 9th 15th centuries AD were 1 2 C higher than those of the mid-20th century. It is argued that, although they derive from artificial conditions, if used appropriately the abundant records from occupation sites represent an important source of local terrestrial palaeoclimatic information which is easily available in the short term, though confirmatory data from natural deposits should also be sought. The potential of the bugs (Hemiptera) is particularly emphasised. The recent return to the north of some species presumed to have been driven south in the ‘Little Ice Age’ is discussed.
We present global fields of decadal annual surface temperature anomalies, referred to the period 1951-1980, for each decade from 1881-1890 to 1981-1990 and for 1984-1993. In addition, we show decadal calendar-seasonal anomaly fields for the warm decades 1936-1945 and 1981-1990. The fields are based on sea surface temperature (SST) and land surface air temperature data. The SSTs are corrected for the pre-World War II use of uninsulated sea temperature buckets and incorporate adjusted satellite-based SSTs from 1982 onward. The generally cold end of the nineteenth century and start to the twentieth century are confirmed, toegether with the substantial warming between about 1920 and 1940. Slight cooling of the northern hemisphere took place between the 1950s and the mid-1970s, although slight warming continued south of the equator. Recent warmth has been most marked over the northern continents in winter and spring, but the 1980s were warm almost everywhere. -from Authors
April-August temperatures are reconstructed from maximum latewood density and ring-width data for a tree-line site in the Canadian Rockies of Alberta close to Athabasca Glacier. The chronology primarily utilizes Picea engelmannii with some Abies lasiocarpa snags. This reconstruction (AD 1073-1983) is the longest densitometrically based summer temperature record from boreal North America. Mean temperatures from 1101- 1900 were 0.71°C below the 1961-1990 reference period and 0.33°C below the 1891-1990 mean of the instru mental record. The coldest interval was the first half of the nineteenth century and the major cold intervals, c. 1200-1350, 1690s and the nineteenth century, coincide with local and regional periods of glacier expansion. Warmer periods, c. 1350-1440 and in the present century, are also periods of higher tree-line or tree-line advance at the site. The 1961-1990 reference period is clearly warmer than any equivalent-length period over the last 800 years. This record of summer warmth reinforces evidence of significant warming at several high- altitude and high-latitude sites around the Northern Hemisphere in the late twentieth century. The reconstruction also indicates that glacier advances of the 'Little Ice Age' in the Rockies occurred during a period of fluctuating climatic conditions rather than a long period of sustained cold of several centuries duration.
Holocene glacier fluctuations at the northern sector of Hardangerjøkulen, central-southern Norway, are reconstructed from four radiocarbon-dated lake and terrestrial sites in the Finse region. For the first time, detailed information has been obtained concerning the number, age and magnitude of Scandinavian glacier variations from the early to mid-Holocene. The deglaciation of the continental ice sheet occurred prior to 9100BP, after which the glacier readvanced and deposited terminal moraines beyond the 'Little Ice Age' maximum limits. At 8600 BP, the glacier retreated before another readvance occurred that culminated at 7600 BP. Except for a glacier advance bracketed to 6300-5300 BP, there are no indications for the existence of glaciers on the Hardangerjøkulen Plateau during the interval 7500-4800 BP. The period 4800-3800 BP was characterized by high-frequency glacier fluctuations of small local glaciers, with the largest minor advance bracketed between 4100 and 3800 BP. Since c. 3800 BP, glaciers have existed continuously on the Hardangerjøkulen Plateau and, after c. 2900 BP, sediments deposited by meltwater from these glaciers are found on the top of all investigated sites along the modern drainage route. Prior to the 'Little Ice Age' readvance, which at Blåisen is maximum dated to 575 ± 75 BP (cal. AD 1305-(1400)-1420), two minor glacier oscillations occurred about 1100 and 700BP.
We present a combined heat- and ice-flow model, constrained by measurements of temperature in the Greenland Ice Sheet Project 2 (GISP2) borehole and by the GISP2 51so record and depth-age scale, which determines a history of temperature, accumulation rate, and ice sheet elevation for the past 50,000 years in central Greenland. Important results are: that the temperature increase from average glacial to Holocene conditions was large, approximately 15 øC, with a 20 øC warming from late glacial to Holocene; that the average accumulation rate during the last glacial maximum (between 15 and 30 kyr B. P.) was 5.5 to 7 cm yr -1, approximately 25% of the modern accumulation rate; that long-term (500-1000 years) averaged accumulation rate and temperature have been inversely correlated during the most recent 7 millennia of the Holocene; and that the Greenland Ice Sheet probably thickened during the aleglacial transition. The inverse correlation of accumulation rate and temperature in the mid and late Holocene suggests that the Greenland Ice Sheet is more prone to volume reduction in a warmed climate than previously thought and demonstrates that accumulation rate is not a reliable proxy for temperature. The elevation history of the ice sheet is poorly constrained by the model, and independent evidence is needed. We also present a simple estimate of the response time for thinning of the interior region of an ice sheet due to retreat of its margins. This was approximately 1900 years for central Greenland during deglaciation.
Solar total and ultraviolet (UV) irradiances are reconstructed annually from 1610 to the present. This epoch includes the Maunder Minimum of anomalously low solar activity (circa 1645-1715) and the subsequent increase to the high levels of the present Modern Maximum. In this reconstruction, the Schwabe (11-year) irradiance cycle and a longer term variability component are determined separately, based on contemporary solar and stellar monitoring. The correlation of reconstructed solar irradiance and Northern Hemisphere (NH) surface temperature is 0.86 in the pre-industrial period from 1610 to 1800, implying a predominant solar influence. Extending this correlation to the present suggests that solar forcing may have contributed about half of the observed 0.55°C surface warming since 1860 and one third of the warming since 1970.
Climatic changes resulting from greenhouse gases will be superimposed on natural climatic variations. High-resolution proxy records of past climate can be used to extend our perspective on regional and hemispheric changes of climate back in time by several hundred years. Using historical, tree-ring and ice core data, we examine climatic variations during the period commonly called the 'Little Ice Age'. The coldest conditions of the last 560 years were between AD 1570 and 1730, and in the nineteenth century. Unusually warm conditions have prevailed since the 1920s, probably related to a relative absence of major explosive volcanic eruptions and higher levels of greenhouse gases.
A compilation of paleoclimate records from lake sediments, trees, glaciers, and marine sediments provides a view of circum-Arctic
environmental variability over the last 400 years. From 1840 to the mid-20th century, the Arctic warmed to the highest temperatures
in four centuries. This warming ended the Little Ice Age in the Arctic and has caused retreats of glaciers, melting of permafrost
and sea ice, and alteration of terrestrial and lake ecosystems. Although warming, particularly after 1920, was likely caused
by increases in atmospheric trace gases, the initiation of the warming in the mid-19th century suggests that increased solar
irradiance, decreased volcanic activity, and feedbacks internal to the climate system played roles.
Information can be inferred on the timing and amplitude of solar total irradiance changes over 1880- 1993 by simulating the global terrestrial surface temperature changes produced by these irradiance changes and comparing them with observed temperatures. The profiles of solar irradiance variations used in the climate simulations are adopted from several different proxies: (1) the length of the sunspot cycle, (2) the mean sunspot number, and (3) a composite proxy that includes the two previous indicators plus the equatorial solar rotation rate, the fraction of penumbral spot coverage, and the rate of decay of the sunspot cycle. We use a seasonal energy-conservation climate/upwelling-diffusion ocean model, forced by the assumed profiles of solar total irradiance variations, combined with variations in anthropogenic greenhouse gases. Optimized cases imply total irradiance changes during 1880-1993 in the range 0.18%-0.77%.If the solar irradiance profiles found from the climate simulations are required to be consistent with recent satellite observations, then the composite solar profile reconstructed by Hoyt & Schatten, combined with the anthropogenic greenhouse forcing, explains the highest fraction of the variance of observed global mean temperatures. In this case, the solar and greenhouse combination accounts for 92% of the observed long-term temperature variance during 1880-1993. The simulation implies that the solar part of the forcing alone would account for 71% of the global mean temperature variance, compared to 51% for the greenhouse gases' part alone. It also suggests a solar total irradiance variation of 0.5% during the interval 1880-1993. Such an amplitude of solar total irradiance change is consistent with astrophysical limits of brightness changes on timescales of decades to centuries independently derived from observations of solar-type stars (including the Sun).
A detailed stable-isotope record is presented for the full length of the Greenland Ice-core Project Summit ice core covering the last 250,000 years according to a graduated timescale. It appears that the climatic stability of the Holocene is the exception rather than the rule; the last interglacial is also noted to have lasted longer than is implied by the deep-sea SPECMAP record. This discrepancy may be accounted for if the climate instability at the outset of the last interglacial delayed the melting of the Saalean ice sheets in America and Eurasia.
THERE has been considerable debate about the magnitude of the decrease in temperature1,2 and the change in precipitation3 in the African tropics during the last glacial period. With the advent of fossil pollen studies in equatorial regions, it is now generally agreed that the temperature did decrease at this time in tropical regions4, but the magnitude of the temperature fluctuations and discrepancies between the continental5 and marine6 temperature records have yet to be resolved7. Here we present new quantitative estimates of temperature and precipitation using a multivariate analysis8 of pollen time-series data from peat deposits in Burundi for the past 40,000 years9. For the last glacial period, our estimate of a temperature decrease of 4 +/- 2 °C is less than those (ranging from 5 to 8 °C) derived from snow-line and tree-line records5,7. Model simulations7 indicate that the snow-line and tree-line estimates (from high-elevation sites at ~4,000 m above sea level) are incompatible with the marine temperature record. Our lower estimate from a site of intermediate elevation may help resolve the differences between these records. We also estimate that the mean annual rainfall decreased by 30% during the last glacial period, in agreement with the rainfall history inferred from lake level fluctuations10.
A Schmidt hammer was used in conjunction with lichenometry to examine the relative age of the outermost Neoglacial moraines in front of glaciers in the Jotunheimen mountains of southern Norway. Particular attention was directed at (1) the magnitude of the ‘Little Ice Age’ glacier expansion episode relative to any others of Neoglacial age, and (2) the potential and limitations of the Schmidt hammer in the context of Holocene glacial chronologies. Schmidt hammer R-values were measured at 34 glaciers and the sizes of the lichen Rhizocarpon geographicum agg. at 80 glaciers. Unusually low R-values and large lichens suggest the occurrence of pre- ‘Little lce Age’ Neoglacial moraines at only a small minority (< 10 %) of the sampled glaciers. The traditional model of relatively large southern Norwegian glaciers during the ‘Little Ice Age’ is substantiated and it is tentatively suggested that differences in climate or glacier type may account for a regional difference in the status of the ‘Little Ice Age’ between northern and southern Scandinavia. The incorporation of weathered boulders into ‘Little Ice Age’ moraines by glacier push mechanisms, and the altitudinally-related variation in boulder surface textures, are identified as major sources of potential error in the use of the Schmidt hammer R-values for relative-age determination of Neoglacial surfaces.
A continuous record of Holocene glacier fluctuations cannot be obtained with the techniques currently in use, which are mostly based on the dating of moraines. The likelihood of obtaining a continuous record by studying sediment cores taken from lakes receiving glacial meltwater is discussed. Sediments from four lakes receiving glacial meltwater are discussed, and then compared with sediments from a lake not receiving glacial meltwater. Characteristic differences were observed in the inorganic content of the sediments: sediments from non-glacial lakes were much more homogenous.
Detailed mapping of well-preserved moraine systems fronting 23 small glaciers in the Kebnekaise Mountains in Swedish Lapland reveals that the Holocene was punctuated by four prolonged intervals of glacier expansion. The youngest interval corresponds to the well-known Little Ice Age and lasted from at least A. D. 1500 until the 20th century. Minor fluctuations superimposed on this broad interval of expansion are dated by lichenometry and historical records; they culminated about A.D. 1916, 1890, 1850, 1780, 1710, and 1500 to 1640. The next youngest interval, which also involved a number of minor fluctuations spread over several centuries, is associated with C¹⁴ dates of 2320±160 years B. P. (St-3811) and 2460±90 years B. P. (I-6854) (Corrected for variation in atmospheric C¹⁴: 2370 and 2475–2720 years B. P., respectively). The two oldest glacial intervals center around tentative lichenometric dates of 5000 and 8000 years B. P., respectively.
Advances of the two older intervals were the least extensive. Advances of the two youngest intervals were approximately equal in magnitude although the relative extents of drift sheets suggest that in many cases the older of these two intervals may have been slightly more intense. Within the Little Ice Age the advances between A. D. 1500 and 1640 were commonly the most extensive.
Two features commonly encountered in the Kebnekaise Mountains point to the complexity of moraine construction. The first involves large moraine ridges that were built up over a time span of up to 8000 years by proximal enlargement of an original moraine obstruction by drift related to successively younger advances. The second feature involves numerous moraines that have survived documented glacier overriding essentially intact.
The climate record kept in ice and in sediment reveals that since the invention of agriculture some 8000 yr ago, climate has remained remarkably stable. By contrast, during the preceding 100,000 yr, climate underwent frequent, very large, and often extremely abrupt shifts. Furthermore, these shifts occurred in lockstep across the globe. They seem to be telling us that Earth's climate system has several distinct and quite different modes of operation and that it can jump from one of these modes to another in a matter of a decade or two. So far, we know of only one element of the climate system which has multiple modes of operation: the oceans' thermohaline circulation. Numerous model simulations reveal that this circulation is quite sensitive to the freshwater budget in the high-latitude regions where deep waters form. Perhaps the mode shifts revealed in the climate record were initiated in the sea. This discovery complicates predictions of the consequences of the ongoing buildup of greenhouse gases in the atmosphere. If the major climate changes of glacial time came as the result of mode shifts, can we be certain that the warming will proceed smoothly? Or is it possible that about 100 years from now, when our descendants struggle to feed the 15 or so billion Earth inhabitants, climate will jump to a less hospitable state. It is difficult to comprehend the misery that would follow on the heels of such an event!
Historical information indicates a glacial advance around AD 1340. Several advances are documented to the first half of the 18th century. Advances are well-dated to 1748, 1868-1873, 1880-1890, 1909-1911 and 1921-1931. Lichenometric dates on moraines from Lappland indicate that moraines were open to lichen immigration around 1650, 1700-1720, 1780, 1800-1810, 1850-1860, 1880-1890, 1910-1920 and 1930. Periods of glacier expansion are dated to about 7500, 6300, 5600, 5100, 4800, 4500, 3000, 2200, 1900, 1400, 1050, 600 and 430 BP. -from Author
The paper reviews various kinds of geoecological change in the tree-limit ecotone of the Scandes Mountains during the period 1970-95. The focus of the study is a part of a regional network of sites intended for long-term tree-limit monitoring, with special stress on effects of climatic variability. The elevational tree-limits of Betula pubescens ssp. tortuosa, Picea abies and Pinus sylvestris, which rose in response to the climatic amelioration earlier this century, now show clear symptoms of increasing climatic stress and disturbance. This manifests as defoliation, growth recession and reproductive failure, locally leading to some initial elevational tree-limit retraction (unbalanced mortality). Defoliation was preceded by decades of weak summer cooling and an increasingly maritime climate, but recently it correlates significantly with low winter soil temperatures, causing death of needles, shoots and buds. In some habitats, Betula pubescens has suffered from mechanical stress and disturbance by increased snow accumulation. Tree-limit decline is paralleled by analogous responses of high-elevation boreal forests as well as the ground cover, encompassing elevational range-limit retraction of certain plant species, deterioration of alpine/subalpine dwarf-shrub heaths and terricolous lichen mats. These processes coincide with indications of enhanced periglacial activity, chiefly wind deflation of frost-heaved top-soils at exposed sites. Presumably, reindeer trampling and grazing play a certain role in the latter context, although this disturbance interacts with climate cooling and increased storminess. Short-term extreme events, particularly concerning winter climate (e.g. ground frost), represent previously underrated disturbance mechanisms in cold-stressed, high-altitude boreal forest. The results suggest mechanisms of tree-layer regression, which lag behind the most severe stresses and disturbances by decades and make cold-marginal trees increasingly sensitive to climatic extremes and, in addition, unable to respond progressively to later positive weather anomalies, due to major defoliation and hypothetical xylem cavitation. The recorded changes are logical in consequence of the irregular climatic cooling and a more maritime climate since the late 1930s. In a wider perspective, the results fit a current pattern of natural geoecological destabilization and rapid vegetation change in the North Atlantic region. In addition, the results are discussed in the perspective of global climate change and biogeographical records over the past few decades.
Land rent assessments from western Norway and documents concerned with applications for their reduction provide detailed information about the incidence of landslides, rockfalls, and avalanches, as well as floods, during the period of the Little Ice Age. The nature and reliability of the available data is discussed and is shown to be adequate to demonstrate a much increased incidence of major mass movements and floods which started in the late 17th century and continued into the 19th century in valleys adjacent to Jostedalsbre. This environmental change began abruptly and there was a striking concentration of disastrous incidents between 1650 and 1760 and in certain years during that period, such as 1687, 1693, and 1702.
In 1945 Storglaciären located in the Kebnekaise massif, northern Sweden, was selected for a long term study of the climatic impact on glaciers and an annual mass balance programme was initiated. Since the mass balance year 1945-1946 the average annual winter precipitation has increased by 0.53 m water equivalent (w. eq.), the annual average ablation has decreased by 0.58 m w. eq., and the annual average net balance has increased from -0.80 m w. eq./year to +0.30 m w. eq./year. The decrease in ablation is caused by a decrease in summer temperature of about 1°C. In addition, frontal retreat has decreased the low altitude area of the glacier and hence contributed to this decrease in ablation. A comparison with results from mass balance studies at three additional glaciers in the Kebnekaise area show that Storglaciären is representative for the area. The mass balance of Storglaciären is also positively correlated with each of four Norwegian glaciers, although accumulation and net balance are better correlated than ablation. Correlations become less positive with increasing distance between sites. Glacier front measurements provide filtered and delayed indications of climatic changes. Small glaciers are at present in balance with the climate. However, retreating fronts of large glaciers show that they are still adjusting to the major warming of the first half of the 1900s.
In this paper Holocene climatic changes recorded in Lappland, northern Sweden, are described. Recorded changes are dated in three different ways: (1) moraines fronting alpine glaciers are dated lichenometrically, (2) lacustrine sediments, in which the silt content varies with size fluctuations of a small glacier, are C14 dated, and (3) variations in altitude of the pine tree limit are C14 dated. The advantages and limitations of the three techniques are discussed and the results of the studies are compared. In general, the results obtained in these three ways are consistent and are interpreted in climatic terms. The area around Vuolep Allakasjaure probably became deglaciated just before 9000 B.P. About 8600 B.P. climate began an improvement which culminated between 7000 and 6000 B.P. Shorter fluctuations are superimposed on this long-term climatic change. The most pronounced periods of relatively cold climate occurred about 7500-7300 B.P., 4500 B.P., 2800-2200 B.P., and during recent centuries. Variations in the composition of sediments in cores from Vuolep Allakasjaure indicate that the glacier in the drainage basin fluctuated frequently in size.
Detailed mapping of well-preserved moraine systems fronting 23 small glaciers in the Kebnekaise Mountains in Swedish Lapland reveals that the Holocene was punctuated by four prolonged intervals of glacier expansion. The youngest interval corresponds to the well-known Little Ice Age and lasted from at least A. D. 1500 until the 20th century. Minor fluctuations superimposed on this broad interval of expansion are dated by lichenometry and historical records; they culminated about A. D. 1916, 1890, 1850, 1780, 1710, and 1500 to 1640. The next youngest interval, which also involved a number of minor fluctuations spread over several centuries, is associated with C14 dates of 2320± 160 years B. P. (St-3811) and 2460± 90 years B. P. (I-6854) (Corrected for variation in atmospheric C14: 2370 and 2475-2720 years B. P., respectively). The two oldest glacial intervals center around tentative lichenometric dates of 5000 and 8000 years B. P., respectively. Advances of the two older intervals were the least extensive. Advances of the two youngest intervals were approximately equal in magnitude although the relative extents of drift sheets suggest that in many cases the older of these two intervals may have been slightly more intense. Within the Little Ice Age the advances between A. D. 1500 and 1640 were commonly the most extensive. Two features commonly encountered in the Kebnekaise Mountains point to the complexity of moraine construction. The first involves large moraine ridges that were built up over a time span of up to 8000 years by proximal enlargement of an original moraine obstruction by drift related to successively younger advances. The second feature involves numerous moraines that have survived documented glacier overriding essentially intact.
Glacial and non-glacial (control) lakes are used to reconstruct a continuous record of Holocene glacier variations from C-14-dated glacio-lacustrine sediments in four distal glacial lakes from southern Norway. Silt/clay bands (commonly 5-10 cm thick), characterized by low organic content, high X-ray density, high mineral magnetic susceptibility and high natural remanent magnetisation (NRM) intensity, are attributed to enhanced minerogenic sedimentation following glacierization of the catchment. These glacigenic bands are different from thinner (0-2 cm) minerogenic laminations found in both glacial and non-glacial lakes with steep slopes in the catchment. Glaciers disappeared from at least three of the catchments shortly after 9000 BP and remained absent throughout the 'Climatic Optimum' of the early- to mid-Holocene. Relatively large glaciers and higher-altitude glaciers formed earlier, existed longer and/or exhibited more Neoglacial expansion episodes. Glaciers existed in the lake catchments at least during the following intervals: Midtivatnet, 3400-3000, 2200-2100, and after 1000 BP; Gjuvvatnet, 6400-5900, 3000-2600, 2500-2300, 1600-1400, and for two intervals after 750 BP; Flatbrevatnet II, continuously since 4900 BP; Storevatnet. one interval after 1000 BP. All glaciers attained their Neoglacial maxima during the last major Neoglacial expansion episode (the 'Little Ice Age'). This pattern implies a response to a fluctuating but generally deteriorating climate during the mid- to late-Holocene.
The focus of this study is the possible correlation between changes in the climate of Scandinavian and changes in solar irradiation. Reliable information about Holocene climatic change in Sweden and Norway is currently available from two main sources: the 14C dating of pine wood retrieved from above the present pine-tree limit and studies of glacier variations based on proglacial lacustrine sediments and on moraines. The reconstructed alpine tree-limit reveals that summer temperature in general was warmer during the early Holo cene than it was during the late Holocene. Superimposed on this general trend are several fluctuations of a few hundred years' duration. Relatively cold periods with a duration of the order of 300-600 years occurred frequently during the Holocene. In this paper, dates of the major climatic events are compared with an index of solar activity, the so-called δ14C anomalies. For most of the last 9000 years a good correspondence is demonstrated between the timing of cold events in Scandinavia and the timing of major δ14 C anomalies (low solar irradiation). The general Holocene cooling trend is believed to be partly a result of land uplift following deglaciation and partly a result of orbitally forced changes in irradiation. Large fluctuations in Scandinavian summer temperature can be reconciled with the pattern of climatic change presented in several recent studies in the North Atlantic region. A link between these areas could be provided by changes in the production of North Atlantic Deep Water.
Critical evidence is presented for the timing and extent of Holocene glacier variations in southern Norway based on end-moraine stratigraphy and 22 new 14C dates. Dates have been obtained from moss layers, other plant remains, peat and soil associated with outermost moraines delimiting the Neoglacial maximum extent of four glaciers in the Jotunheimen-Jostedalsbreen region. There is conclusive evidence for a late Neoglacial ('Little Ice Age') maximum within the last 400-600 years; maximum age estimates for outer moraines are AD 1516 (Sagabreen), 1450 (Storbreen), 1440 (Bøverbreen) and about 1424 (Haugabreen). The last three glaciers have not exceeded their 'Little Ice Age' limits since at least 3205 ± 60, 5670 ± 80 and 6470 ± 80 BP, respectively. Onset of peat growth at these times is consistent with a deteriorating climate after the 'Climatic Optimum' of the early Holocene. Subsequent deterioration is indicated by the accumulation at Bøverbreen of poorly-humified peat from 4295 ± 49 to at least 3250 ± 70 BP, and from 1740 ± 60 to at least 1300 ± 60 BP. Southern Norwegian glaciers appear to have been larger at their 'Little Ice Age' maxima than at any time since regional deglaciation about 9000 BP. It is inferred that the relatively large scale of the 'Little Ice Age' glacier expansion in southern Norway was related to the most southerly migration of oceanic and atmospheric polar fronts since the early Holocene.
Sedimentary sequences from glacial lakes in southern Norway provide a new approach to the reconstruction of a relatively complete record of Holocene glacier and climatic variations. The data show that, following the "Climatic Optimum" of the early Holocene, neoglaciation was asynchronous; glaciers formed at different times at different sites, depending on critical altitudinal thresholds in relation to the scale of climatic variations. Neoglaciation began as early as ca. 6400 yr B.P. at Gjuvvatnet, ca. 3400 yr B.P. at Midtivatnet, and later than ca. 1000 yr B.P. at Storevatnet. These differences in glacierization provide a key to reconstructing the fluctuating decline in mean summer temperature (relative to the present) from at least +1 °C during the mid-Holocene to below -2 °C in the "Little Ice Age."
Radiocarbon-dated glacial deposits from several different areas of the
world indicate that alpine glaciers and ice caps in parts of both the
Northern and Southern Hemispheres expanded in response to climate change
in early Holocene time. These data suggest that a worldwide episode of
cooler climate similar in scope to the more recent Neoglaciation
occurred ca. 8,500-7,500 yr B.P.
Lithostratigraphic and paleobotanical studies suggest that the Jostedalsbreen ice cap probably disappeared during the early Holocene Hypsithermal interval (ca. 8000-6000 B.P.) and re-formed about 5300 B.P. The equilibrium-line altitude was lower than the modern mean equilibrium-line altitude between 2595 ±85 and 2360 ±80 B.P., between 2250 ±65 and 2150 ±80 B.P., between 1740 ±75 and 1730 ±75 B.P., between 1430 ±45 and 1270 ±60 B.P., and subsequent to 890 ±60 B.P. The outlet valley glaciers reached their maximum Neoglacial extent during the Little Ice Age in the middle of the eighteenth century.
Evidence from the advances and retreats of alpine glaciers during the Holocene suggests that there were at least 14 century-timescale cool periods similar to the recent Little Ice Age. Here, we examine the hypothesis that these cool periods were caused by reductions in solar irradiance. A statistically significant correlation is found between the global glacial advance and retreat chronology of Röthlisberger and variations in atmospheric ¹⁴ C concentration. A simple energy-balance climate model is used to show that the mean reduction of solar irradiance during times of maximum ¹⁴ C anomaly like the Maunder Minimum would have to have been between 0.22 and 0.55 % to have caused these cool periods. If a similar solar irradiance perturbation began early in the 21st century, the associated climate effects would be noticeable, but still considerably less than those expected to result from future greenhouse gas concentration increases.
The most prominent Holocene climatic event in Greenland ice-core proxies, with approximately half the amplitude of the Younger Dryas, occurred ˜8000 to 8400 yr ago. This Holocene event affected regions well beyond the North Atlantic basin, as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane. Widespread proxy records from the tropics to the north polar regions show a short-lived cool, dry, or windy event of similar age. The spatial pattern of terrestrial and marine changes is similar to that of the Younger Dryas event, suggesting a role for North Atlantic thermohaline circulation. Possible forcings identified thus far for this Holocene event are small, consistent with recent model results indicating high sensitivity and strong linkages in the climatic system.
An up-to-date Table is provided of the monthly and seasonal means representative of the air over central England from 1659 onward, incorporating some minor revisions and extensions of the earlier Table (Manley 1953 and 1959). Comments on its construction, and on the prospect of further extension backward in time, are added.
δ 18O and δ 13C values for several species of planktonic foraminifera and calcareous nannofossils from Recent deep-sea sediments have been studied in order to evaluate their paleoceanographic and paleotemperature potential. Nannofossils from Indian Ocean core-tops reflect isotopic temperatures as warm as, or warmer than, the temperatures reported by Williams et al. (1977) for shallow-dwelling planktonic foraminifera from the same samples. In general, deep-sea sediment samples from the world's major oceans indicate that nannofossil δ 18O values are from 0.5 to 1 ‰ heavier than shallow-dwelling planktonic foraminifera. Although nannofossil δ 18O values depart from thermodynamic equilibrium with oceanic surface water temperatures, the δ 18O temperature trend parallels that of surface-dwelling planktonic foraminifera.
Presented is a review of studies investigating factors affecting climatic changes in the Earth's atmosphere--past, present, and future. Dating methods, particularly the Oxygen 18/16 method, are discussed. (SL)
PREVIOUS studies on two deep Greenland ice cores have shown that a long series of climate oscillations characterized the late Weichselian glaciation in the North Atlantic region1, and that the last glacial cold period, the Younger Dryas, ended abruptly 10,700 years ago2. Here we further focus on this epoch-defining event, and present detailed heavy-isotope and dust-concentration profiles which suggest that, in less than 20 years, the climate in the North Atlantic region turned into a milder and less stormy regime, as a consequence of a rapid retreat of the sea-ice cover. A warming of 7 °C in South Greenland was completed in about 50 years.
In the northeastern St. Elias Mountains in southern Yukon Territory and Alaska, C14-dated fluctuations of 14 glacier termini show two major intervals of Holocene glacier expansion, the older dating from 3300-2400 calendar yr BP and the younger corresponding to the Little Ice Age of the last several centuries. Both were about equivalent in magnitude. In addition, a less-extensive and short-lived advance occurred about 1250-1050 calendar yr BP (A.D. 700–900). Conversely, glacier recession, commonly accompanied by rise in altitude of spruce tree line, occurred 5975–6175, 4030-3300, 2400-1250, and 1050-460 calendar yr BP, and from A.D. 1920 to the present. Examination of worldwide Holocene glacier fluctuations reinforces this scheme and points to a third major interval of glacier advances about 5800-4900 calendar yrs BP; this interval generally was less intense than the two younger major intervals. Finally, detailed mapping and dating of Holocene moraines fronting 40 glaciers in the Kebnekaise and Sarek Mountains in Swedish Lapland reveals again that the Holocene was punctuated by repeated intervals of glacier expansion that correspond to those found in the St. Elias Mountains and elsewhere. The two youngest intervals, which occurred during the Little Ice Age and again about 2300–3000 calendar yrs BP, were approximately equal in intensity. Advances of the two older intervals, which occurred approximately 5000 and 8000 calendar yr BP, were generally less extensive. Minor glacier fluctuations were superimposed on all four broad expansion intervals; those of the Little Ice Age culminated about A.D. 1500–1640, 1710, 1780, 1850, 1890, and 1916. In the mountains of Swedish Lapland, Holocene mean summer temperature rarely, if ever, was lower than 1°C below the 1931–1960 summer mean and varied by less than 3.5°C over the last two broad intervals of Holocene glacial expansion and contraction.
The termination of the Last Glaciation, the Lateglacial period, was characterised by highly unstable climates which, in northern Europe, oscillated between warm temperate and arctic conditions. Different indicators of past climate have provided contrasting views on the timing and intensity of these climatic changes. Here we present preliminary reconstructions of the thermal climate interpreted from subfossil coleopteran assemblages from Britain, Norway, Sweden and Poland, in which regional differences can be ascribed to the varying influence of, (a) the North Atlantic surface water temperatures, (b) the proximity of the Fennoscandian ice sheet and (c) the ice free continent. Quantification of the thermal climate enables these local differences to be resolved.
Planktonic foraminiferal studies have been carried out on 28 piston cores of late Pleistocene age from the western Gulf of Mexico, an area of high sedimentation rates. For the interval between 73 × 10 ³ and 95 × 10 ³ yr BP, two of these cores have sedimentation rates of 12 and 15 cm/1000 yr. Calculation of the speed of faunal changes within this interval reveals an extremely rapid paleoclimatic-paleooceanographic change at approximately 90 × 10 ³ years BP. Several species including distinctly warm-sensitive forms, then disappeared from the Gulf of Mexico in less than 350 yr, leaving a depleted planktonic foraminiferal fauna greatly dominated by only three species with little apparent temperature preference. This fauna existed for 2.5 × 10 ³ yr after which distinctly cooler water elements increased in abundance rapidly and formed a high frequency peak approx 83.5–85 × 10 ³ years BP. This increase in cooler water elements reflects either a return to more stable environmental conditions or a lag in their migration to the Gulf of Mexico after the severe climatic cooling, rather than further cooling.
The faunal event in the Gulf of Mexico correlates with an even more spectacular event recorded in the Greenland ice sheet by a drop in ¹⁸ O values within a time interval of only about 100 yr (Dansgaard et al. , 1971, 1972). A possibly correlative climatic event of similarly rapid nature has also been reported for speleothems from southern France (Duplessy et al. , 1970).
The paleoclimatic event is closely associated stratigraphically with a widespread volcanic ash layer, although it is possibly significant that the increased volcanism occurred 1000 yr after the paleoclimatic event. A rapid lowering of the lysocline occurs simultaneously with the paleoclimatic event although faunal diversity is low in the succeeding fauna despite decreased calcium carbonate solution. Both the association with volcanism and changes in the position of the lysocline may be significant in consideration of mechanisms of such rapid climatic changes. In turn, such rapid paleoclimatic-paleooceanographic changes as observed in tropical Gulf of Mexico cores, in the Greenland ice sheet and in caves of southern France must be considered in the evaluation of causal mechanisms of glacial and interglacial oscillations.
Quantitative estimates of 1480 years of summer temperatures in northern Fennoscandia have previously been derived from continuous treering records from northern Sweden. Here we show the results of spectral analyses of these data. Only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub-periods. Relatively timestable peaks are apparent at periods of 2.1, 2.5, 3.1, 3.6, 4.8, 32–33 and for a range between 55–100 years. These results offer no strong evidence for solar-related forcing of summer temperatures in these regions. Our previously published reconstruction was limited in its ability to represent long-timescale temperature change because of the method used to standardize the original tree-ring data. Here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales. Considerable variance is now reconstructed on timescales of several centuries. In comparison with modern normals (1951–70) generally extended periods when cool conditions prevailed, prior to the start of the instrumental record, include 500–700, 790–870, 1110–1150, 1190–1360, 1570–1750 (A.D.) with the most significant cold troughs centred on about 660, 800, 1140, 1580–1620 and 1640. Predominantly warm conditions occurred in 720–790, 870–1110 and 1360–1570 with peaks of warmth around 750, 930, 990, 1060, 1090, 1160, 1410, 1430, 1760 and 1820.
Long-term changes in the level of solar activity are found in historical records and in fossil radiocarbon in tree-rings. Typical of these changes are the Maunder Minimum (A.D. 1645–1715), the Sprer Minimum (A.D. 1400–1510), and a Medieval Maximum (c. A.D. 1120–1280). Eighteen such features are identified in the tree-ring radiocarbon record of the past 7500 years and compared with a record of world climate. In every case when long-term solar activity falls, mid-latitude glaciers advance and climate cools; at times of high solar activity glaciers recede and climate warms. We propose that changes in the level of solar activity and in climate may have a common cause: slow changes in the solar constant, of about 1% amplitude.
The valleys surrounding the Jostedalsbreen ice cap were deglaciated during the latter half of the Preboreal Chronozone. At the end of the Preboreal Chronozone, however, a glacier readvance occurred. Terminal moraines were deposited by outlet valley glaciers from the Jostedalsbreen Plateau up to 1 km beyond Little Ice Age moraines. Inferred from the altitude of lateral moraines formed during this readvance and calculations of the equilibrium-line altitude (ELA) depression based on an accumulation area ratio (AAR) of 0.6, the average depression of the ELA was m below the present. By assuming a similar precipitation pattern as at present, this suggests a mean temperature decline of about 2°C. Palynological investigations from Sygneskardet, Sunndalen, indicate that climate like the present was achieved just after 9000 BP. The Holocene climatic optimum occurred during the Atlantic Chronozone, with elm (Ulmus) stands growing at the present birch (Betula) forest limit in Sunndalen and pine (Pinus) growing at Styggevatnet to an altitude of at least 1160 m. During this period the mean summer temperature is estimated to have been at least 2.7 and 1.8°C warmer than at present, with and without the local climatic effect of Jostedalsbreen, respectively. An inferred rise of the ELA of about 400 m from the present altitude suggests that possibly no glaciers existed on the Jostedalsbreen Plateau during the Holocene climatic optimum. Vegetational changes as deduced from palynological studies, lowered tree limits and increased resedimentation in peat bogs indicate general climatic deterioration since the Late Atlantic Chronozone.
Measured 18O/16O ratios from the Greenland Ice Sheet Project 2 (GISP2) ice core extending back to 16,500 cal yr B.P. provide a continuous record of climate change since the last glaciation. High-resolution annual 18O/16O results were obtained for most of the current millennium (A.D. 818-1985) and record the Medieval Warm Period, the Little Ice Age, and a distinct 11-yr 18O/16O cycle. Volcanic aerosols depress central Greenland annual temperature (∼1.5°C maximally) and annual 18O/16O for about 4 yr after each major eruptive event. On a bidecadal to millennial time scale, the contribution of solar variability to Holocene Greenlandic temperature change is ∼0.4°C. The role of thermohaline circulation change on climate, problematic during the Holocene, is more distinct for the 16,500-10,000 cal yr B.P. interval. (Analogous to 14C age calibration terminology, we express time in calibrated (cal) yr B.P. (A.D. 1950 = 0 cal yr B.P.)). The Oldest Dryas/Bølling/Older Dryas/Allerød/Younger Dryas sequence appears in great detail. Bidecadal variance in 18O/16O, but not necessarily in temperature, is enhanced during the last phase of lateglacial time and the Younger Dryas interval, suggesting switches of air mass transport between jet stream branches. The branched system is nearly instantaneously replaced at the beginning of the Bølling and Holocene (at ∼14,670 and ∼11,650 cal yr B.P., respectively) by an atmospheric circulation system in which 18O/16O and annual accumulation initially track each other closely. Thermodynamic considerations of the accumulation rate-temperature relationship can be used to evaluate the 18 O/16O-temperature relationship. The GISP2 ice-layer-count years of major GISP2 climate transitions also support the use of coral 14C ages for age calibration.
An oxygen isotope temperature record over a large part of the past 30,000 yr has been obtained for the southern Cape Province of South Africa by combining data on the isotopic composition of a stalagmite from a deep cave with that of a confined groundwater aquifer in the same region. Results show that temperatures during the last glacial maximum were on average about 6°C lower than those today, with peaks up to 7°C lower. A detailed analysis of the past 5000 yr suggests multiple fluctuations, with generally lower temperatures (1–2°C) around 4500 and 3000 yr B.P. The carbon isotopic composition of the stalagmite indicates significant vegetation changes between the late Pleistocene and today, and also during the second half of the Holocene.