Designing policies to mitigate the agricultural contribution to climate change: an assessment of soil based carbon sequestration and its ancillary effects

Soil carbon sequestration has been regarded as a cheap and cost-effective way to sequester carbon until other technologies to tackle climate change become available or more cost-effective. An assessment of the social desirability of a soil carbon sequestration policy requires the consideration of all associated social costs and benefits. Measures to re-accumulate carbon in soils have ancillary or co-effects on the environment that can be beneficial or detrimental to social welfare and few of which are traded in markets. This paper discusses issues related to the development of soil carbon sequestration policies into agri-environmental schemes and reports findings from an application of a choice experiment to elicit preferences and estimate benefits of a soil carbon programme in Scotland under consideration of co-effects on biodiversity and rural viability. Preferences for soil carbon based mitigation are found to be heterogeneous and related to beliefs about climate change and attitudes towards its mitigation. Benefit estimates suggest that including co-effects can significantly change the outcome of cost?Cbenefit tests. Implications for the development of climate change policies are discussed.     

Analysis with C- and X-band satellite SAR data of the Portalet landslide area

This paper describes the use of the Stable Point Network technique, a Persistent Scatterer Interferometry SAR technique, for the analysis of the Portalet landslide area (Central Pyrenees, Spain). For this purpose, different SAR datasets acquired by ERS-1, ERS-2, ENVISAT and TerraSAR-X satellites have been analysed. The use of different SAR images acquired by satellite radar sensors operating at different microwave lengths has allowed for a comparative assessment and illustration of the advantages and disadvantages of these satellites for landslide detection and monitoring. In the introduction, differential interferometry and the study area are briefly described. Then the specifics of the SPN processing and the results of the different datasets are described and compared. In Analysis of the results: the Portalet landslide area, the Portalet landslide area is introduced and the radar displacement measurements are analysed with available geo-information data. Additionally, X-band measurements are compared with those gathered by a ground-based SAR for a previous project. Finally, the most relevant conclusions of this work are discussed.     

Seismic modelling study of a subglacial lake

We characterize the seismic response of Lake Vostok, an Antarctic subglacial lake located at nearly 4 km depth below the ice sheet. This study is relevant for the determination of the location and morphology of subglacial lakes. The characterization requires the design of a methodology based on rock physics and numerical modelling of wave propagation. The methodology involves rock-physics models of the shallow layer (firn), the ice sheet and the lake sediments, numerical simulation of synthetic seismograms, ray tracing, τ–p transforms, and AVA analysis, based on the theoretical reflection coefficients. The modelled reflection seismograms show a set of straight events (refractions through the firn and top-ice layer) and the two reflection events associated with the top and bottom of the lake. Theoretical AVA analysis of these reflections indicates that, at near offsets, the PP-wave anomaly is negative for the ice/water interface and constant for the water/sediment interface. This behaviour is shown by AVA analysis of the synthetic data set. This study shows that subglacial lakes can be identified by using seismic methods. Moreover, the methodology provides a tool for designing suitable seismic surveys.     

Nature of dark energy and polarization measurements

High sensitivity polarization measures, on wide angular scales, together with data on anisotropy, can be used to fix DE parameters. In this paper, first of all, we aim to determine the sensitivity needed to provide significant limits. Our analysis puts in evidence that there is a class of DE models that polarization measures can possibly exclude soon. This class includes models with DE due to a Ratra–Peebles (RP) potential. Using a likelihood analysis, we show that it is possible to distinguish RP models from ΛCDM and other dynamical DE models, already with the sensitivity of experiments like SPOrt or WMAP, thanks to their negative TE correlation at low-l, when the optical depth τ is sufficiently large. On the contrary, fixing the energy scale Λ for RP potentials or distinguishing between ΛCDM and other DE potentials requires a much lower pixel noise, that no planned polarization experiment will achieve. While reviewing this paper after the referee report, the first-year WMAP data were released. WMAP finds large positive anisotropy–polarization correlations at low l; this apparently excludes DE models with RP potentials.     

Optical spectroscopy of X-Mega targets – II. The massive double-lined O-type binary HD 93205

A new high-quality set of orbital parameters for the O-type spectroscopic binary HD 93205 has been obtained combining échelle and coudé CCD observations. The radial velocity orbits derived from the He  ii λ 4686 Å (primary component) and He  i λ 4471 Å (secondary component) absorption lines yield semi-amplitudes of 133±2 and 314±2 km s⁻¹ for each binary component, resulting in minimum masses of 31 and 13 M_⊙ ( q =0.42) . We also confirm for the binary components the spectral classification of O3 V+ O8 V previously assigned. Assuming for the O8 V component a 'normal' mass of 22–25 M_⊙ we would derive for the primary O3 V a mass of 'only' 52–60 M_⊙ and an inclination of about 55° for the orbital plane. We have also determined for the first time a period of apsidal motion for this system, namely 185±16 yr using all available radial velocity data sets of HD 93205 (from 1975 to 1999). Phase-locked variations of the X-ray emission of HD 93205 consisting of a rise of the observed X-ray flux near periastron passage are also discussed.     

A multidisciplinary investigation of deep-seated landslide reactivation triggered by an extreme rainfall event: a case study of the Monesi di Mendatica landslide,Ligurian Alps

Landslides - In November 2016, an extreme rainfall event affected the Ligurian Alps (NW Italy). Consequently, several landslides and debris flows occurred in the upper Tanarello stream basin. In...