Abstracts on Global Climate Change

Jun 2005

Variations in tropical convection as an amplifier of global climate change at the millennial scale

Ivanochko, TS Ganeshram, RS Brummer, GJA Ganssen, G Jung, SJA Moreton, SG Kroon, D


The global expression of millennial-scale climatic change during the glacial period and the persistence of this signal in Holocene records point to atmospheric teleconnections as the mechanism propagating rapid climate variations. We suggest rearrangements in the tropical convection system globally affected the concentration and location of atmospheric water vapour and modulated terrestrial and marine emissions of CH4 and N2O, providing a tropical mechanism of amplifying and perpetuating millennial-scale climate changes. A multi-proxy reconstruction reflecting various aspects of the intensity of the Arabian Sea Summer Monsoon shows strong millennial-scale variability over the past 90 kyr in which low intensity is associated with a southern shift of the Intertropical Convergence Zone (ITCZ) and an eastward shift in the equatorial convergence zone. The monsoon reconstruction, which is based on new data from a Somali margin sediment core, is supported by previously reported tropical paleoclimatic records and suggests that global scale millennial climatic variability is in part driven by modulations in the tropical hydrological cycle and tropical emissions of the greenhouse gases CH4 and N2O. (c) 2005 Elsevier B.V. All rights reserved.

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North Atlantic weather oscillation and human infectious diseases in the Czech Republic, 1951-2003

Hubalek, Z


Longitudinal correlation between the North Atlantic Oscillation large-scale weather system (NAO) and the annual incidence rate of 14 viral, bacterial and protozoan national notifiable human diseases in the Czech Republic was examined. In simple correlation, cases of salmonellosis, erysipelas, infectious mononucleosis and toxoplasmosis were positively correlated with the winter NAO index, while hepatitis A and shigellosis were negatively correlated, and the other diseases tested (rubella, mumps, chickenpox., tick-borne encephalitis, Lyme borreliosis, leptospirosis, tularemia and scarlet fever) were uncorrelated with NAO. However, 8 of the 14 diseases also revealed a significant time trend, either increasing (infectious mononucleosis, salmonellosis, erysipelas, toxoplasmosis) or decreasing (hepatitis A, scarlet fever, leptospirosis, shigellosis) during the period. When the effect of NAO on incidence of the diseases was then controlled for calendar year using partial correlation analysis and detrended regression, only toxoplasmosis and infectious mononucleosis were found significantly positively correlated with the NAO when the index was lagged 1 or 2 years, and leptospirosis was correlated negatively with a lag of 2 years. Large-scale weather changes as described by NAO therefore do not seem to be a crucial factor in the fluctuation of annual incidence rate of the majority of tested infectious diseases in the Czech Republic, while other factors, especially social and public health circumstances, are obviously more important.

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Responses of deciduous forest trees to severe drought in Central Europe

Leuzinger, S Zotz, G Asshoff, R Korner, C

TREE PHYSIOLOGY 25:6 641-650

In 2003, Central Europe experienced the warmest summer on record combined with unusually low precipitation. We studied plant water relations and phenology in a 100-year-old mixed deciduous forest on a slope (no ground water table) near Basel using the Swiss Canopy Crane (SCC). The drought lasted from early June to mid September. We studied five deciduous tree species; half of the individuals were exposed to elevated CO2 concentration ([CO2]) (530 ppm) using a free-air, atmospheric CO2-enrichment system. In late July, after the first eight weeks of drought, mean predawn leaf water potential about 30 m above ground was -0.9 MPa across all trees, dropping to a mean of -1.5 MPa in mid-August when the top 1 m of the soil profile had no plant accessible moisture. Mean stomatal conductance and rates of maximum net photosynthesis decreased considerably in mid-August across all species. However, daily peak values of sap flow remained surprisingly constant over the whole period in Quercus petraea (Matt.) Liebl., and decreased to only about half of the early summer maxima in Fagus sylvatica L. and Carpinus betulus L. (stomatal down-regulation of flux). Although we detected no differences in most parameters between CO2-treated and control trees, predawn leaf water potential tended to be less negative in trees exposed to elevated [CO2]. Leaf longevity was greater in 2003 compared with the previous years, but the seasonal increase in stem basal area reached only about 75% of that in previous years. Our data suggest that the investigated tree species, particularly Q. petraea, did not experience severe water stress. However, an increased frequency of such exceptionally dry summers may have a more serious impact than a single event and would give Q. petraea a competitive advantage in the long run.

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Effects of shore height, wave exposure and geographical distance on thermal niche width of intertidal fauna

Davenport, J Davenport, JL


Environmental temperature is a controlling factor in ecology and is influenced by global climate change. Upper/lower thermal limits for 10 species of. sessile/sedentary invertebrates were established on a single rocky shore. Two species with different reproductive strategies (Littorina littorea, Nucella lapillus) from 3 Scottish and 3 Irish shores were investigated to test effects of small scale (< 10 km) or larger scale (ca. 500 km) distances, and shore height on upper lethal temperature. At 3 sheltered and 3 exposed shores in Ireland, thermal responses of N. lapillus from the middle of their vertical distribution were compared. Amongst the 10 species from a single shore, thermal niche width rose asymptotically with maximum height of distribution on the shore and maximum emersion time. Median upper lethal temperature and median lower lethal temperature were closely correlated. For 8 species on the middle and upper shore, there were significant linear relationships between shore height and the variables upper lethal temperature, lower lethal temperature and thermal niche width. L. littorea upper lethal temperature was found not to vary with shore height, varied little over small geographical distances, but was significantly higher in Ireland than in Scotland. N, lapillus upper lethal temperature was higher in animals collected from the upper limit of distribution on the shore than in dogwhelks from the lower limit of distribution, was higher in animals taken from sheltered shores than from exposed shores and showed significant local differences. Upper lethal temperature was higher in Scottish than Irish dogwhelks.

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Uncertainty assessment of spatial patterns of soil organic carbon density using sequential indicator simulation, a case study of Hebei province, China

Zhao, YC Shi, XZ Yu, DS Wang, HJ Sun, WX

CHEMOSPHERE 59:11 1527-1535

The spatial patterns of soil organic carbon (SOC) are closely related to the global climate change. In quantifying the spatial patterns of SOC density, the concept of uncertainty of the SOC density values at unsampled locations is particularly important because such uncertainty can be propagated into the subsequent global climate change modelling and has fundamental impacts on the ultimate results of the model. A total of 361 SOC density data of topsoil (0-20 cm) in Hebei province and sequential indicator simulation (SIS) were applied to perform a conditional stochastic simulation in this study to quantitatively assess the uncertainty of mapping SOC density. The results showed that a great variation exists in the SOC density data. The conditional variance of 500 realizations generated by SIS was larger in mountainous areas of the study area where the SOC density fluctuated the most, and the uncertainty was smaller on the plain area where SOC density was consistently small. Realizations generated by SIS can represent the possible spatial patterns of SOC density without smoothing effect. A set of realizations can be used to explore all possible spatial patterns of SOC density and provide a visual and quantitative measure of the spatial uncertainty of mapping SOC density. With a given threshold of SOC density, SIS can quantitatively assess both local uncertainty and spatial uncertainty of SOC density that is greater the threshold. (c) 2005 Elsevier Ltd. All rights reserved.

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Detriments to post-bleaching recovery of corals

McClanahan, TR Maina, J Starger, CJ Herron-Perez, P Dusek, E

CORAL REEFS 24:2 230-246

Predicting the response of coral reefs to large-scale mortality induced by climate change will depend greatly on the factors that influence recovery after bleaching events. We experimentally transplanted hard corals from a shallow reef with highly variable seawater temperature ( 23 - 36 degrees C) to three unfished marine parks and three. shed reefs with variable coral predator abundance and benthic cover. The transplanted corals were fragmented colonies collected from a reef that was relatively undisturbed by the 1997 - 1998 warm-water temperature anomaly, one of the most extreme thermal events of the past century, and it was assumed that they would represent corals likely to succeed in the future temperature environment. We examined the effects of four taxa, two fragment sizes, an acclimation period, benthic cover components, predators and tourists on the survival of the coral fragments. We found the lowest survival of transplants occurred in the unfished marine parks and this could be attributed to predation and not tourist damage. The density of small coral recruits approximately 6 months after the spawning season was generally moderate ( similar to 40 - 60/m(2)), and not different on fished and unfished reefs. Coral recovery between 1998 and 2002 was variable ( 0 - 25%), low ( mean of 6.5%), and not different between fished and unfished reefs. There was high variability in coral mortality among the three unfished areas despite low variation in estimates of predator biomass, with the highest predation occurring in the Malindi MNP, a site with high coralline algal cover. Stepwise multiple regression analysis with 14 variables of coral predators and substratum showed that coralline algae was positively, and turf algae negatively associated with mortality of the transplants, with all other variables being statistically insignificant. This suggests that alternate food resources and predator choices are more important than predator biomass in determining coral survival. Nonetheless, large predatory fish in areas dominated by coralline algae may considerably retard recovery of eurythermal corals. This will not necessarily retard total hard coral recovery, as other more predator-tolerant taxa can recover. Based on the results, global climate change will not necessarily favor eurythermal over stenothermal coral taxa in remote or unfished reefs, where predation is a major cause of coral mortality.

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Fire in African savanna: Testing the impact of incomplete combustion on pyrogenic emissions estimates

Smith, AMS Wooster, MJ Drake, NA Dipotso, FM Perry, GLW


African savannah fires are key sources of trace gases and aerosols, yet their true magnitude remains relatively poorly constrained. Here we present a detailed investigation of the amount of unburned material remaining in the ash produced by such fires, and examine whether this quantity needs to be considered when calculating atmospheric emissions. Emissions estimates for individual fires are usually based upon a calculation of the amount of fuel biomass combusted, usually estimated via a “simple subtraction” of the pre- and post-fire fuel loads. However, certain studies have concluded that this approach leads to gross overestimation of emissions, by perhaps 100%, due to the fact that a proportion of unburned fuel normally remains in the “charred” ash and that the simple subtraction method fails to take this fully into account. Whilst this latter point is true, we show that the mathematical relationship used previously to calculate the implications of this for emissions calculation is flawed. We demonstrate a new first-principles derivation of the quantity of mass combusted, taking into account any fuel remaining in the ash via measurement of ash mass loss on ignition (LOI). Using data from dry-season experimental fires in Botswana, we compared estimates of biomass combusted calculated via our LOI-based method to those obtained via the simple subtraction approach. We found a mean difference of < 10%, far less than the factor of 2 difference obtained when using the previous erroneous formula. Similar results are obtained for carbon and nitrogen emissions, and the findings are further supported by reassessment of previous data from early-to-mid-dry season savanna fires in Tanzania. These results indicate that the simple subtraction method overestimates emissions by far less than previously suggested, and that the method is likely to provide sufficient accuracy in most situations where emissions calculations are required. For fires where very substantial amounts of unburned material are expected to remain within the ash, and where an LOI-based approach to emissions calculation may therefore be particularly warranted, it is important that the correct formula derived herein is used, since errors inherent in the previous formula increase with increasing ash LOI.

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Forecasting climate change effects on salamander distribution in the highlands of central Mexico

Parra-Olea, G Martinez-Meyer, E de Leon, GFP

BIOTROPICA 37:2 202-208

A generalized decline of amphibian populations is occurring worldwide. The causes for such a decline are not completely understood; however, climate change has been identified as a possible cause for amphibian extinction, among others. Ecological niche modeling has proven to be a useful tool to predict potential distribution of species in the context of climatic changes. In this paper, we used the Genetic Algorithm for Rule-set Prediction (GARP) to model the potential distributions of two species of plethodontid salamanders: Pseudoeurycea cephalica and P leprosa. We projected their potential distributions under climatic scenarios expected in 50 yr based on a conservative scenario of global climate change and assuming a moderate dispersal ability for both species. Our analyses suggest that climate change effects may pose an additional long-term risk to both species of plethodontid salamanders, with a more dramatic scenario in the case of P leprosa. By the year 2050, this species may lose almost 75 percent of its distributional area, and this projection is even worse when deforestation (in the way it is occurring at present) is considered within the predicted model. Our results concur with those obtained for species with limited dispersal capability because they do not track changing climates, but rather face a loss of distributional area. The survival of these species is not secure, even though their potential distributional area falls within a considerable number of natural protected areas.

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Interdisciplinary oceanographic observations: the wave of the future

Dickey, TD Bidigare, RR

SCIENTIA MARINA 69: Suppl. 1 23-42

Oceanographic measurements, though difficult and expensive, are essential for effective study, stewardship, preservation, and management of our oceanic and atmospheric systems. Ocean sciences have been driven by technologies enabling new observations, discoveries, and modelling of diverse interdisciplinary phenomena. Despite rapid advances in ocean sampling capabilities, the numbers of disciplinary variables that are necessary to solve oceanographic problems are large and increasing. In addition, the time and space scales of key processes span over ten orders of magnitude; presently, there remain major spectral gaps in our sampling. Thus, undersampling presents the main limitation to our understanding of global climate change; variability in fish biomass and regime shifts; and episodic and extreme events. Fortunately, recent advances in ocean platforms and in situ autonomous sampling systems and satellite sensors are enabling unprecedented rates of data acquisition as well as the expansion of temporal and spatial coverage. Consequently, improved sampling strategies will lead to a reduction in ocean forecasting error for predictions of a multitude of atmospheric and oceanic processes. Nonetheless, major challenges remain to massively increase the variety and quantity of ocean measurements and to effectively coordinate, synthesize, and distribute oceanographic data sets. In particular, numbers of measurements are limited by the costs of instruments and their deployment as well as data processing and production of useful data products and visualizations. Looking forward, many novel and innovative technologies involving computing, nanotechnology, robotics, information and telemetry technologies, space sciences, and molecular biology are being developed at a fast pace for numerous applications (Kaku, 1997; Kurzweil, 1999). It is anticipated that several of these can and will be transitioned to the ocean sciences and will prove to be extremely beneficial for oceanographers in the next few decades. Already, autonomous, ‘robotic’ in situ sampling, high spectral resolution optical and chemical instrumentation, multi-frequency acoustics, and biomolecular techniques are being utilized by a limited number of oceanographers. Also, increased temporal and spatial sampling capabilities for expanding numbers of interdisciplinary variables are being accelerated thanks to both new technologies and utilization of data assimilation models coupled with autonomous sampling platforms. Data networks coupled with internet connectivity are rapidly increasing access to and utilization of data sets. In this essay, we review recent technological progress for solving some key oceanographic problems and highlight some of the foreseeable challenges and opportunities of ocean science technologies and their applications.

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Risk in irrigation water supply and the effects on food production

Cai, XM


This paper examines irrigation water supply deficit and associated risk indicators due to random climate events and potential effects on irrigated food production during the period 1996 to 2025 for seven river basins in the USA, China, and India. An integrated water and food model with global scope is applied for the analysis. The global climate regime during 1961 to 1990 is used to generate 30 climatic scenarios for the time period 1996 to 2025, and these scenarios are applied to the model in order to characterize the randomness of precipitation, runoff, and evapotranspiration, which affects both irrigation water supply and demand. The risk with random climate events is represented by reliability, variability, and vulnerability from different perspectives. Regarding irrigation water supply, Colorado will bear an increasingly unstable situation although the average water supply relative to the demand will maintain at a relatively high level; selected basins in China and India indicate that significantly lower levels of reliability and more deleterious affects from drought can be expected, but under a less variable condition due to assumed water storage increase. From 1996 to 2025, the effects of water deficits on irrigated food production are characterized with a nonlinear phenomenon and food production loss will be more sensitive to irrigation water supply deficit in the future. Future work following this paper needs to consider the impact of global climate change and the water quality of the irrigation return flow and result verification by local studies.

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Water-saving approaches for improving wheat production

Deng, XP Shan, L Inanaga, S Inoue, M


The greatest fear of global climate change is drought. World-wide, 61% of countries receive rainfall of less than 500 mm annually; domestication of wheat first occurred in such a semiarid region of southwestern Asia, and it seems that wheat foods originally came from dryland gardens. Wheat plants respond to drought through morphological, physiological and metabolic modifications in all plant parts. At the cellular level, plant responses to water deficit may result from cell damage, whereas other responses may correspond to adaptive processes. Although a large number of drought-induced genes have been identified in a wide range of wheat varieties, a molecular basis for wheat plant tolerance to water stress remains far from being completely understood. The rapid translocation of abscissic acid (ABA) in shoots via xylem flux, and the increase of ABA concentration in wheat plant parts cot-relate with the major physiological changes that occur during plant response to drought. It is widely accepted that ABA mediates general adaptive responses to drought. For a relatively determinate target stress environment, and with stable genotype x environment interaction, the probability for achieving progress is high. This approach will be possible only after we learn more about the physiology and genetics of wheat plant responses to water stress and their interactions. The difficulties encountered by molecular biologists in attempting to improve crop drought tolerance are due to our ignorance in agronomy and crop physiology and not to lack of knowledge or technical expertise in molecular biology. (c) 2005 Society of Chemical Industry.

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