Impact of CO2 fertilization on maximum foliage cover across the globe's warm, arid environments

Satellite observations reveal a greening of the globe over recent decades. The role in this greening of the "CO2 fertilization" effect-the enhancement of photosynthesis due to rising CO2 levels-is yet to be established. The direct CO2 effect on vegetatio

Revisiting the parameterization of potential evaporation as a driver of long-term water balance trends

We examine the effects of two different parameterizations of potential evaporation on long-term trends in soil moisture, evaporative flux and runoff simulated by the water balance model underlying the Palmer Drought Severity Index. The first, traditiona

The impact of bushfires on water yield from south-east Australia's ash forests

Widespread disturbance within forested catchments typically increases runoff. However, following widespread fire in 1939 throughout south-east Australia, Kuczera (1987) reported persistent reductions in runoff that were attributed to increased evapotrans

A small remark on Bernstein’s theorem

We investigate splitting-type variational problems with some linear growth conditions. For balanced solutions of the associated Euler– Lagrange equation, we receive a result analogous to Bernstein’s theorem on non-parametric minimal surfaces. Without assumptions of this type, Bernstein’s theorem cannot be carried over to the splitting case, which follows from an elementary counterexample. We also include some modifications of our main theorem

Changes in the variability of global land precipitation

In our warming climate there is a general expectation that the variability of precipitation (P) will increase at daily, monthly and inter-annual timescales. Here we analyse observations of monthly P (1940-2009) over the global land surface using a new theoretical framework that can distinguish changes in global P variance between space and time. We report a near-zero temporal trend in global mean P. Unexpectedly we found a reduction in global land P variance over space and time that was due to a redistribution, where, on average, the dry became wetter while wet became drier. Changes in the P variance were not related to variations in temperature. Instead, the largest changes in P variance were generally found in regions having the largest aerosol emissions. Our results combined with recent modelling studies lead us to speculate that aerosol loading has played a key role in changing the variability of P

Expanding the Wahhabi mission: Saudi Arabia, the Islamic University of Medina and the transnational religious economy

This thesis offers a historical account of the emergence and evolution of new Islamic educational institutions in Saudi Arabia in the twentieth century which came to sit at the heart of migratory circuits of students and scholars from across the globe. It pays special attention to the Islamic University of Medina (IUM), which was launched by the Saudi state in 1961 to offer fully-funded religious instruction to mostly non-Saudi students. Exploring the history of this missionary project provides a point of departure for interrogating the commonplace claim that Saudi actors have taken advantage of wealth derived from oil rents in recent decades to fund the export of Wahhabism. In order to understand the far-reaching cultural, social and political dynamics that have emerged from this nexus between migration, education, material investment and religious mission, this study develops a historiography grounded in a novel conception of transnational religious economies. These are understood to consist in flows – both within and across national borders – of material capital, spiritual capital, religious migrants and social technologies. While Saudi state spending has been crucial for the operation of institutions like the IUM, its missionary project has also drawn on a far wider range of resources within the terms of these economies, including migrant labour, sources of symbolic legitimation and modes of pedagogy appropriated from beyond the Peninsula. The IUM’s syllabuses, whilst firmly rooted in core Wahhabi concerns, have also been shaped by processes of hegemonic engagement with migrant students. Finally, students bearing spiritual capital accumulated on its campus have themselves made divergent uses of these resources in locations around the world. The notion of transnational religious economies developed here shines light on the multiple resources, border crossings, historical contingencies, interests and forms of agency bound up in the articulation of a power-laden, state-led project of “religious expansion”

A general framework for understanding the response of the water cycle to global warming over land and ocean

Climate models project increases in globally averaged atmospheric specific humidity that are close to the Clausius"Clapeyron (CC) value of around 7%K-1 whilst projections for mean annual global precipitation (P) and evaporation (E) are somewhat muted at around 2%K-1. Such global projections are useful summaries but do not provide guidance at local (grid box) scales where impacts occur. To bridge that gap in spatial scale, previous research has shown that the "wet get wetter and dry get drier" relation, Δ(P -E)αP -E, follows CC scaling when the projected changes are averaged over latitudinal zones. Much of the research on projected climate impacts has been based on an implicit assumption that this CC relation also holds at local (grid box) scales but this has not previously been examined. In this paper we find that the simple latitudinal average CC scaling relation does not hold at local (grid box) scales over either ocean or land. This means that in terms of P -E, the climate models do not project that the "wet get wetter and dry get drier" at the local scales that are relevant for agricultural, ecological and hydrologic impacts. In an attempt to develop a simple framework for local-scale analysis we found that the climate model output shows a remarkably close relation to the long-standing Budyko framework of catchment hydrology. We subsequently use the Budyko curve and find that the local-scale changes in P -E projected by climate models are dominated by changes in P while the changes in net irradiance at the surface due to greenhouse forcing are small and only play a minor role in changing the mean annual P -E in the climate model projections. To further understand the apparently small changes in net irradiance we also examine projections of key surface energy balance terms. In terms of global averages, we find that the climate model projections are dominated by changes in only three terms of the surface energy balance: (1) an increase in the incoming long-wave irradiance, and the respective responses (2) in outgoing longwave irradiance and (3) in the evaporative flux, with the latter change being much smaller than the former two terms and mostly restricted to the oceans. The small fraction of the realised surface forcing that is partitioned into E explains why the hydrologic sensitivity (2%K-1) is so much smaller than CC scaling (7%K -1). Much public and scientific perception about changes in the water cycle has been based on the notion that temperature enhances E. That notion is partly true but has proved an unfortunate starting point because it has led to misleading conclusions about the impacts of climate change on the water cycle. A better general understanding of the potential impacts of climate change on water availability that are projected by climate models will surely be gained by starting with the notion that the greater the enhancement of E, the less the surface temperature increase (and vice versa). That latter notion is based on the conservation of energy and is an underlying basis of climate model projections

Interspecific interactions of the sea urchin Parechinus angulosus and the effect of variations in microhabitat availability

Intertidal populations of the sea urchin Parechinus angulosus were examined at seven sites along the south and east coasts of South Africa. At the five southerly sites, P. angulosus occurred in allopatry, while, at the two northerly sites, it occurred in sympatry with several species of Indopacific sea urchins. At the five southerly sites, there was a significant correlation of number of sea urchins per pool with the surface area of the overhang in that pool. This relationship broke down for P. angulosus at the two northerly sites, where there was a significant correlation between these two factors for Stomopneustes variolaris. The density of populations of P. angulosus at the two northerly sites, although not significantly different from all five southerly sites, were considerably lower. There was a significant difference between the mean size of populations at the seven sites. Although no direct evidence is available, a competitive interaction between these two species is proposed to explain the observed patterns of microhabitat utilization and densities. Two series of manipulative experiments were conducted at Kowie Point, where P. angulosus occurs in sympatry, The first, involved urchin removals from three experimental sites. The percentage cover of four functional algal groups was monitored in three experimental and three unaltered control sites over a three month period in spring (Sept. - Dec.) 1993. Two 100 point 0,25m² random point quadrats were thrown at each of the six sites at approximately monthly intervals over the experimental period. Since initial cover of algae varied at the six sites, ANOVA's of the change in percentage cover of four functional algal groups were used to determine treatment effects. No treatment effects were identified for any of the four functional algal groups. There was a strong negative correlation between the percentage cover of foliose algae and encrusting coralline algae, suggesting the possibility of a competitive relationship between them. The second, involved the experimental manipulation of microhabitat availability. The blocking of overhangs, by means of cement filled bags, resulted in an approximate 50% decrease in the total number of urchins in the two experimental pools, and the two control pools without overhangs. However, in the control pool with overhangs there was a slight increase in the number of urchins over the same period. Clearly, the presence of suitable shelters, is a prerequisite for the maintenance of dense intertidal population of P. angulosus. It is proposed that, due to the exposed nature of the South African coast, intertidal populations of P.angulosus are restricted to inhabiting suitable shelters from which they emerge to feed on passing drift algae. The implications of these findings are discussed in terms of current ecological literature