Atmospheric Angular Momentum Time-Series: Characterization of their Internal Noise and Creation of a Combined Series

The atmosphere induces variations in Earth rotation. These effects are classically computed using the “angular momentum approach”. In this method, the variations in Earth rotation are estimated from the variations in the atmospheric angular momentum (AAM). Several AAM time-series are available from different meteorological centers. However, the estimation of atmospheric effects on Earth rotation differs when using one atmospheric model or the other. The purpose of this work is to build an objective criterion that justifies the use of one series in particular. Because the atmosphere is not the only cause of Earth rotation variations, this criterion cannot rely only on a comparison of AAM series with geodetic data. Instead, we determine the quality of each series by making an estimation of their noise level, using a generalized formulation of the “three-cornered hat method”. We show the existence of a link between the noise of the AAM series and their correlation with geodetic data: a noisy series is usually less correlated with Earth orientation data. As the quality of the series varies in time, we construct a combined AAM series, using time-dependent weights chosen so that the noise level of the combined series is minimal. To determine the influence of a minimal noise level on the correlation with geodetic data, we compute the correlation between the combined series and Earth orientation data. We note that the combined series is always amongst the best correlated series, which confirms the link established before. The quality criterion, while totally independent of Earth orientation observations, appears to be physically convincing when atmospheric and geodetic data are compared     

The Limits of Economic Benefits: Adding Social Affordances to the Analysis of Trophy Hunting of the Khwe and Ju/’hoansi in Namibian Community-Based Natural Resource Management

In the global neoliberal ecological discourse, trophy hunting proponents often articulate the economic benefits it creates for local communities, especially through jobs and meat. Trophy hunting revenues are also crucial to support the overall operational costs of community-based natural resource management (CBNRM). The aim of this paper is to show that this rather simplified dominant discourse, based only on “benefits”, sells short the local realities of the Khwe and Ju/’hoansi Bushmen (San) in the Bwabwata National Park and the Nyae Nyae Conservancy, Namibia, respectively. Building on Gibson, I use the concept of “social affordances” as an addition to economic benefits. This leads me to argue for an expansion of the debate beyond the limits of economic benefits to the human domain, to better understand the multiple experiences, perceptions, power relations and meanings (for good and ill) of local actors on trophy hunting and its main players.