Extreme events in a changing climate: Variability is more important than averages

Extreme events act as a catalyst for concern about whether the climate is changing. Statistical theory for extremes is used to demonstrate that the frequency of such events is relatively more dependent on any changes in the variability (more generally, the scale parameter) than in the mean (more generally, the location parameter) of climate. Moreover, this sensitivity is relatively greater the more extreme the event. These results provide additional support for the conclusions that experiments using climate models need to be designed to detect changes in climate variability, and that policy analysis should not rely on scenarios of future climate involving only changes in means.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Gypsum as a monitor of the paleo-limnological–hydrological conditions in Lake Lisan and the Dead Sea

The isotopic composition and mass balances of sources and sinks of sulfur are used to constrain the limnological–hydrological evolution of the last glacial Lake Lisan (70–14 ka BP) and the Holocene Dead Sea. Lake Lisan deposited large amounts of primary gypsum during discrete episodes of lake level decline. This gypsum, which appears in massive or laminated forms, displays δ³⁴S values in the range of 14–28‰. In addition, Lake Lisan’s deposits (the Lisan Formation) contain thinly laminated and disseminated gypsum as well as native sulfur which display significantly lower δ³⁴S values (−26 to 1‰ and −20 to −10‰, respectively). The calculated bulk isotopic compositions of sulfur in the sources and sinks of Lake Lisan lacustrine system are similar (δ³⁴S ≈ 10‰), indicating that freshwater sulfate was the main source of sulfur to the lake. The large range in δ³⁴S found within the Lisan Formation (−26 to +28‰) is the result of bacterial sulfate reduction (BSR) within the anoxic lower water body (the monimolimnion) and bottom sediments of the lake.

Precipitation of primary gypsum from the Ca-chloride solution of Lake Lisan is limited by sulfate concentration, which could not exceed 3000 mg/l. The Upper Gypsum Unit, deposited before ca. 17–15 ka, is the thickest gypsum unit in the section and displays the highest δ³⁴S values (25–28‰). Yet, our calculations indicate that no more than a third of this Unit could have precipitated directly from the water column. This implies that during the lake level decline that instigated the precipitation of the Upper Gypsum Unit, significant amounts of dissolved sulfate had to reach the lake from external sources. We propose a mechanism that operated during cycles of high-low stands of the lakes that occupied the Dead Sea basin during the late Pleistocene. During high-stand intervals (i.e., Marine Isotopic Stages 2 and 4), lake brine underwent BSR and infiltrated the lake’s margins and adjacent strata. As lake level dropped, these brines, carrying ³⁴S-enriched sulfate, were flushed back to the shrinking lake and replenished the water column with sulfate, thereby promoting massive gypsum precipitation.

The Holocene Dead Sea precipitated relatively small amounts of primary gypsum, mainly in the form of thin laminae. δ³⁴S values of these laminae and disseminated gypsum are relatively constant (15 ± 0.7‰) and are close to present-day lake composition. This reflects the lower supply of freshwater to the lake and the limited BSR activity during the arid Holocene time and possibly during former arid interglacials in the Levant.     

Effects of ultrasonic cleaning on the amino acid geochemistry of foraminifera tests

Although investigations into amino acid geochemistry of foraminifera have included the use of ultrasonic cleaners as part of their cleaning procedure, there apparently has been no attempt to determine what effects this procedure may have on the observed chemical changes. This paper presents the results of a time study showing the effects of cleaning on ten protein amino acids and the non-protein alloisoleucine. The data suggest that there are three loosely defined groups which all ultimately undergo an exponential decrease in concentration, but which vary within the initial 45 min of treatment: Group I, stable; Group II, constantly decreasing; Group III, showing slight increases. The observed effects suggest that studies based on amino acid enantiomeric ratios probably are the least affected by procedural errors introduced by ultrasonification.     

Infrasonic Signal Detection and Source Location at the Prototype International Data Centre

—?This paper describes an automatic and interactive data processing system designed to locate impulsive atmospheric sources with a yield of at least one kiloton by detecting and characterizing the airborne infrasound radiated by the source. The infrasonic processing subsystem forms part of a larger system currently under development at the Prototype International Data Center (PIDC) in Arlington, Virginia where seismic, hydroacoustic, radionuclide and infrasonic methods are used to detect and locate impulsive sources in any terrestrial environment. Infrasonic signal detection is achieved via a coincidence detector which requires both the normalized cross correlation and the short-term-average/long-term-average ratio of a beam in the direction of maximum correlation to exceed predetermined threshold values simultaneously before a detection is declared. The infrasound propagation model currently used to infer travel-time information assumes the horizontal sound speed across the ground to be 320.0?m/s. This crude model is currently being replaced by a model which predicts travel-time information through a ray-tracing algorithm for acoustic waves in an atmosphere with seasonal representations for temperature and wind. A novel feature of the source location process is the fusion of all available arrival information, whether it be seismic, hydroacoustic or infrasonic to locate a single source where it is reasonable to hypothesize a common source. In its final configuration the infrasonic subsystem will routinely process data from the global 60-station International Monitoring System (IMS) infrasonic network currently under development.     

The dominance of nucleation: The Jewish experience in the early phase of Jewish settlement

The dominance of the nucleated pattern among Jewish settlement in Palestine is not merely the outcome of central planning. The early colonies, established between 1882 and 1914, were already nucleated, although there was some experimentation with other patterns. The main type of settlement established in this period, with which the present study deals, was themoshava. This freeholder family-farm village was strongly nucleated, and practically all the types which were created after it reveal the impact of its nucleted spatial plan. The attempts to establish dispersed private farms were few, but, even so, their owners resided within the existingmoshavot. They were not, therefore, seperate settlements. Publicly funded training farms were also set-up, and an early, unsuccessful, attempt to establish a cooperative farm also dates to this period. But these were also not genuine settlements. There were, in addition, a number of workers' quarters which were attached to plantation centers or worker settlements attached to existingmoshavot. All these settlement types tended to be nucleated. The discussion of the reasons for the dominance of nucleation is based on an analysis of documents and other sources of the 1882–1914 period. The factors are cultural, communal, and ideological as well as economic. The need for grouping together was stimulated by security and religious needs, but also by lack of experience and insufficient familiarity with the land and its political system. Other factors were the intricate tenurial regulations and farm land use strategies. The availability of adequate documentation for this case provides a fairly unique opportunity for understanding the process of pattern formation.     

Identifying synergies and trade-offs in the sustainability–security nexus: the case of the Israeli–Palestinian wastewater treatment regime

ABSTRACT

The literature on environmental security often stresses the complementarity between sustainability and broader security goals. Less emphasis has been placed on possible trade-offs between security objectives and aspects of sustainability. This study examines the conditions under which these synergies and trade-offs are likely to occur, and how the trade-offs can be reconciled, especially during times of peacebuilding. As a case study, we analyse the effect of Israeli security concerns on environmental infrastructure designed to treat wastewater in the West Bank. This study identifies several sustainability–security trade-offs: (1) economic—in which security concerns raise costs of wastewater infrastructure, thereby crowding-out other potentially productive investments; (2) equity—in which security concerns result in disproportionate exposure of populations to environmental hazards; and (3) environmental—in which security concerns increase ecological footprints. Yet, our case study also indicates that both sides used a variety of creative measures to reconcile these trade-offs.

EDITOR D. Koutsoyiannis GUEST EDITOR K. Aggestam     

Interpretation of spring recession curves

Recession curves contain information on storage properties and different types of media such as porous, fractured, cracked lithologies and karst. Recession curve analysis provides a function that quantitatively describes the temporal discharge decay and expresses the drained volume between specific time limits (Hall 1968). This analysis also allows estimating the hydrological significance of the discharge function parameters and the hydrological properties of the aquifer. In this study, we analyze data from perennial springs in the Judean Mountains and from others in the Galilee Mountains, northern Israel. All the springs drain perched carbonate aquifers. Eight of the studied springs discharge from a karst dolomite sequence, whereas one flows out from a fractured, slumped block of chalk. We show that all the recession curves can be well fitted by a function that consists of two exponential terms with exponential coefficients alpha1 and alpha2. These coefficients are approximately constant for each spring, reflecting the hydraulic conductivity of different media through which the ground water flows to the spring. The highest coefficient represents the fast flow, probably through cracks, or quickflow, whereas the lower one reflects the slow flow through the porous medium, or baseflow. The comparison of recession curves from different springs and different years leads to the conclusion that the main factors that affect the recession curve exponential coefficients are the aquifer lithology and the geometry of the water conduits therein. In normal years of rainy winter and dry summer, alpha1 is constant in time. However, when the dry period is longer than usual because of a dry winter, alpha1 slightly decreases with time.     

Paper 1. the mink methodology: background and baseline

A four step methodology has been developed for study of the regional impacts of climate change and the possible responses thereto. First the region's climate sensitive sectors and total economy are described (Task A, current baseline). Next a scenario of climate change is imposed on the current baseline (Task B, current baseline with climate change). A new baseline describing the climate sensitive sectors and total regional economy is projected for some time in the future (Task C, future baseline, year 2030) in the absence of climate change. Finally, the climate change scenario is reimposed on the future baseline (Task D, future baseline with climate change). Impacts of the climate change scenario on the current and future regional economies are determined by means of simulation models and other appropriate techniques. These techniques are also used to assess the impacts of an elevated CO₂ concentration (450 ppm) and of various forms of adjustments and adaptations. The region chosen for the first test of the methodology is composed of the four U.S. states of Missouri, Iowa, Nebraska and Kansas. The climate change scenario is the actual weather of the 1930s decade in the MINK region. ‘Current’ climate is the actual weather of the period 1951–1980.     

Value of perfect ENSO phase predictions for agriculture: evaluating the impact of land tenure and decision objectives

In many places, predictions of regional climate variability associated with the El Niño–Southern Oscillation phenomenon offer the potential to improve farmers’ decision outcomes, by mitigating the negative impacts of adverse conditions or by taking advantage of favorable conditions. While the notion that climate forecasts are potentially valuable has been established, questions of when they may be more or less valuable have proven harder to resolve. Using simulations, we estimate the expected value of seasonal climate information under alternative assumptions about (a) land tenure (ownership vs. short-term leases) and (b) the decision maker’s objective function (expected utility vs. prospect theory value function maximization), employing a full range of plausible parameter values for each objective function. This allows us to show the extent to which the value of information depends on risk preferences, loss aversion, wealth levels and expectations, as well as situational constraints. Our results demonstrate in a non-laboratory decision context that, in some cases, psychologically plausible deviations from expected utility maximization can lead to substantial differences in estimates of the expected value of climate forecasts. Efforts to foster effective use of climate information and forecasts in agriculture must be grounded in a firm understanding of the goals, objectives and constraints of decision makers.