Centralization Trade-off with Non-Uniform Taxation

When local public goods are provided by a centralized authority, spillovers are internalized, but heterogeneity in preferences may be suppressed. Besley and Coate (2003) recently examined this classic trade-off for a uniform tax regime with strategic delegation. Here, we extend their approach by allowing for a non-uniform tax regime. We find that centralization with nonuniform taxation unambiguously increases welfare in comparison to uniform-tax centralization. With non-cooperative legislators coming from symmetric districts, our centralization dominates decentralization for any degree of spillovers. In other cases, non-uniform taxation at least improves the odds of centralization, if measured by a utilitarian yardstick.decentralization, taxation, local public goods

Centralization Trade-off with Non-Uniform Taxes

When local public goods are provided by a centralized authority, spillovers may be coordinated, but heterogeneity in preferences may be suppressed. Besley and Coate (2003) have already solved this classic trade-off for a uniform tax regime. Here, we extend their approach by allowing for a non-uniform tax regime. We find that centralization with our tax system necessarily increases welfare in comparison to uniform-tax centralization. Importantly, with non-cooperative legislators coming from homogenous districts, our centralization dominates decentralization for any degree of spillovers. In other cases, it at least improves odds of centralization, if measured by utilitarian yardstick.Decentralization; Local Public Goods; Distributive Politics; Political Economy

Using multimedia to enhance the accessibility of the learning environment for disabled students: reflections from the Skills for Access project

As educators' awareness of their responsibilities towards ensuring the accessibility of the learning environment to disabled students increases, significant debate surrounds the implications of accessibility requirements on educational multimedia. There would appear to be widespread concern that the fundamental principles of creating accessible web‐based materials seem at odds with the creative and innovative use of multimedia to support learning and teaching, as well as concerns over the time and cost of providing accessibility features that can hold back resource development and application. Yet, effective use of multimedia offers a way of enhancing the accessibility of the learning environment for many groups of disabled students. Using the development of ‘Skills for Access’, a web resource supporting the dual aims of creating optimally accessible multimedia for learning, as an example, the attitudinal, practical and technical challenges facing the effective use of multimedia as an accessibility aid in a learning environment will be explored. Reasons why a holistic approach to accessibility may be the most effective in ensuring that multimedia reaches its full potential in enabling and supporting students in learning, regardless of any disability they may have, will be outlined and discussed

Combined impact of shifts in Southern Ocean westerlies and Antarctic sea ice during LGM on atmospheric CO2

A significant influence of changes in the westerly winds over the Southern Ocean was proposed as a mechanism to explain a large portion of the glacial atmospheric pCO2 drawdown (Toggweiler et al., 2006). However, additional modelling studies with Earth System Models of Intermediate Complexity do not confirm the size and sometimes even the sign of the impact of southern hemispheric winds on the glacial pCO2 as suggested by Toggweiler (Men- viel et al., 2008; Tschumi et al., 2008, d’Orgeville et al., 2010). We here add to this discussion and explore the potential contribution of changes in the latitudinal position of the winds on Southern Ocean physics and the carbon cycle by using a state-of-the-art ocean general circulation model (MITgcm) in a spatial resolution increasing in the Southern Ocean (2◦ longitude; northern hemisphere: 2◦ latitude; southern hemisphere: 2◦cos(α)). We discuss how the change in carbon cycling is related to the upwelling strength and pattern in the Southern Ocean and how they depend on the changing wind fields and/or the sea ice coverage. While the previous studies explored the impact of the westlies starting from present day or pre-industrial back- ground conditions, we here perform simulations from LGM background climate. Ocean surface conditions are for reasons of consistency taken from output of the COSMOS Earth System model for a pre-industrial control and two LGM runs (Zhang et al., in preparation). Additionally, a northwards shift (by 10◦) of the westerly wind belt as proposed by Toggweiler is investigated

Rapid changes in ice core gas records Part 2: Understanding the rapid rise in atmospheric CO2 at the onset of the Bølling/Allerød

During the last glacial/interglacial transition the Earth's climate underwent rapid changes around 14.6 kyr ago. Temperature proxies from ice cores revealed the onset of the Bølling/Allerød (B/A) warm period in the north and the start of the Antarctic Cold Reversal in the south. Furthermore, the B/A is accompanied by a rapid sea level rise of about 20 m during meltwater pulse (MWP) 1A, whose exact timing is matter of current debate. In situ measured CO₂ in the EPICA Dome C (EDC) ice core also revealed a remarkable jump of 10±1 ppmv in 230 yr at the same time. Allowing for the age distribution of CO₂ in firn we here show, that atmospheric CO₂ rose by 20–35 ppmv in less than 200 yr, which is a factor of 2–3.5 larger than the CO₂ signal recorded in situ in EDC. Based on the estimated airborne fraction of 0.17 of CO₂ we infer that 125 Pg of carbon need to be released to the atmosphere to produce such a peak. Most of the carbon might have been activated as consequence of continental shelf flooding during MWP-1A. This impact of rapid sea level rise on atmospheric CO₂ distinguishes the B/A from other Dansgaard/Oeschger events of the last 60 kyr, potentially defining the point of no return during the last deglaciation

In situ benthic fluxes from an intermittently active mud volcano at the Costa Rica convergent margin

Along the erosive convergent margin off Costa Rica a large number of mound-shaped structures exist built by mud diapirism or mud volcanism. One of these, Mound 12, an intermittently active mud volcano, currently emits large amounts of aqueous dissolved species and water. Chemosynthetic vent communities, authigenic carbonates, and methane plumes in the water column are manifestations of that activity. Benthic flux measurements were obtained by a video-guided Benthic Chamber Lander (BCL) deployed at a vent site located in the most active part of Mound 12. The lander was equipped with 4 independent chambers covering adjacent areas of the seafloor. Benthic fluxes were recorded by repeated sampling of the enclosed bottom waters while the underlying surface sediments were recovered with the lander after a deployment time of one day. One of the chambers was placed directly in the centre of an active vent marked by the occurrence of a bacterial mat while the other chambers were located at the fringe of the same vent system at a lateral distance of only 40 cm. A transport-reaction model was developed and applied to describe the concentration profiles in the pore water of the recovered surface sediments and the temporal evolution of the enclosed bottom water. Repeated model runs revealed that the best fit to the pore water and benthic chamber data is obtained with a flow velocity of 10 cm yr− 1 at the centre of the vent. The flux rates to the bottom water are strongly modified by the benthic turnover (benthic filter). The methane flux from below at the bacterial mat site is as high as 1032 μmol cm− 2 yr− 1, out of which 588 μmol cm− 2 yr− 1 is oxidised in the surface sediments by microbial consortia using sulphate as terminal electron acceptor and 440 μmol cm− 2 yr− 1 are seeping into the overlaying bottom water. Sulphide is transported to the surface by ascending fluids (238 μmol cm− 2 yr− 1) and is formed within the surface sediment by the anaerobic oxidation of methane (AOM, 588 μmol cm− 2 yr− 1). However, sulphide is not released into the bottom water but completely oxidized by oxygen and nitrate at the sediment/water interface. The oxygen and nitrate fluxes into the sediment are high (781 and 700 μmol cm− 2 yr− 1, respectively) and are mainly driven by the microbial oxidation of sulphide. Benthic fluxes were much lower in the other chambers placed in the fringe of the vent system. Thus, methane and oxygen fluxes of only 28 and 89 μmol cm− 2 yr− 1, respectively were recorded in one of these chambers. Our study shows that the aerobic oxidation of methane is much less efficient than the anaerobic oxidation of methane so that methane which is not oxidized within the sediment by AOM is almost completely released into the bottom water. Hence, anaerobic rather than aerobic methane oxidation plays the major role in the regulation of benthic methane fluxes. Moreover, we demonstrate that methane and oxygen fluxes at cold vent sites may vary up to 3 orders of magnitude over a lateral distance of only 40 cm indicating an extreme focussing of fluid flow and methane release at the seafloor