Todd M.C.,University of Sussex |
Cavazos-Guerra C.,Institute for Advanced Sustainability Studies IASS
Atmospheric Environment | Year: 2016
Dust aerosols are an important component of the climate system and a challenge to incorporate into weather and climate models. Information on the location and magnitude of dust emission remains a key information gap to inform model development. Inadequate surface observations ensure that satellite data remain the primary source of this information over extensive and remote desert regions. Here, we develop estimates of the relative magnitude of active dust emission over the Sahara desert based on data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Utilising the unique vertical profile of aerosol characteristics provided by CALIOP our algorithm identifies emission from aerosol extinction and lidar backscatter in the near surface layers. From the long-term CALIOP archive of day and night-time orbits over 2006-13 we construct coarse resolution maps of a new dust emission index (DEI) for the Sahara desert during the peak summer dust season (June to September). The spatial structure of DEI indicates highest emission over a broad zone focused on the border regions of Southern Algeria, Northern Mali and northwest Niger, displaced substantially (~7°) to the east of the mean maximum in satellite-derived aerosol optical depth. In this region night-time emission exceeds that during the day. The DEI maps substantially corroborate recently derived dust source frequency count maps based on back-tracking plumes in high temporal resolution SEVIRI imagery. As such, a convergence of evidence from multiple satellite data sources using independent methods provides an increasingly robust picture of Saharan dust emission sources. Various caveats are considered. As such, quantitative estimates of dust emission may require a synergistic combined multi-sensor analysis. © 2015.
Rovira A.,Spanish University for Distance Education (UNED) |
Rubbia C.,Institute for Advanced Sustainability Studies IASS |
Valdes M.,Technical University of Madrid |
Martinez-Val J.M.,Technical University of Madrid
Energy | Year: 2014
Concentrated solar power presents the drawback of decreasing radiation capture efficiency as the temperature of the receiver increases, because thermal losses increase as well. Low temperature at the receiver is an advantage for radiation concentrators, as they present high capture efficiency, but this fact changes into a drawback because of the low efficiency of the thermodynamic cycles working with a low temperature heat source.An analysis is presented on the performance of real fluids working with such a type of heat sources that can be generated in simple solar thermal units. Both Joule-Brayton cycles and dry-turbine Rankine cycles are considered, using regenerative heat exchangers for heat recovering. The driving force of this research is to look for working fluids with actual thermodynamic characteristics which fit well with temperatures of the heat source and sink. Some unconventional substances, as refrigerant R-125 or SF6, show good performance. They may be suitable at certain regimes of Rankine and Brayton cycles and could work in fast-reacting systems. Of course, differences in the performance of Brayton and Rankine cycles convey differences in the complexity and cost of the components, but they offer a wide field for coherently choosing the working fluid and thermal conditions. © 2014 Elsevier Ltd.
Irvine P.J.,Institute for Advanced Sustainability Studies IASS |
Gregoire L.J.,University of Bristol |
Lunt D.J.,University of Bristol |
Valdes P.J.,University of Bristol
Geoscientific Model Development | Year: 2013
We present a simple method to generate a perturbed parameter ensemble (PPE) of a fully-coupled atmosphere-ocean general circulation model (AOGCM), HadCM3, without requiring flux-adjustment. The aim was to produce an ensemble that samples parametric uncertainty in some key variables and gives a plausible representation of the climate. Six atmospheric parameters, a sea-ice parameter and an ocean parameter were jointly perturbed within a reasonable range to generate an initial group of 200 members. To screen out implausible ensemble members, 20 yr pre-industrial control simulations were run and members whose temperature responses to the parameter perturbations were projected to be outside the range of 13.6 ± 2 C, i.e. near to the observed pre-industrial global mean, were discarded. Twenty-one members, including the standard unperturbed model, were accepted, covering almost the entire span of the eight parameters, challenging the argument that without flux-adjustment parameter ranges would be unduly restricted. This ensemble was used in 2 experiments; an 800 yr pre-industrial and a 150 yr quadrupled CO2 simulation. The behaviour of the PPE for the pre-industrial control compared well to ERA-40 reanalysis data and the CMIP3 ensemble for a number of surface and atmospheric column variables with the exception of a few members in the Tropics. However, we find that members of the PPE with low values of the entrainment rate coefficient show very large increases in upper tropospheric and stratospheric water vapour concentrations in response to elevated CO2 and one member showed an implausible nonlinear climate response, and as such will be excluded from future experiments with this ensemble. The outcome of this study is a PPE of a fully-coupled AOGCM which samples parametric uncertainty and a simple methodology which would be applicable to other GCMs. © 2013 Author(s).
Otero N.,Institute for Advanced Sustainability Studies IASS |
Mohino E.,Complutense University of Madrid |
Gaetani M.,University Pierre and Marie Curie
Climate Dynamics | Year: 2015
At decadal time scales, the capability of state-of-the-art atmosphere-ocean coupled climate models in predicting the precipitation in Sahel is assessed. A set of 14 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) is selected and two experiments are analysed, namely initialized decadal hindcasts and forced historical simulations. Considering the strong linkage of the atmospheric circulation signatures over West Africa with the rainfall variability, this study aims to investigate the potential of using wind fields for decadal predictions. Namely, a West African monsoon index (WAMI) is defined, based on the coherence of low (925 hPa) and high (200 hPa) troposphere wind fields, which accounts for the intensity of the monsoonal circulation. A combined empirical orthogonal functions analysis is applied to explore the wind fields’ covariance modes, and a set of indices is defined on the basis of the identified patterns. The WAMI predictive skill is assessed by comparing WAMI from coupled models with WAMI from reanalysis products and with a standardized precipitation index (SPI) from observations. Results suggest that the predictive skill is highly model dependent and it is strongly related to the WAMI definition. In addition, hindcasts are more skilful than historical simulations in both deterministic and probability forecasts, which suggests an added value of initialization for decadal predictability. Moreover, coupled models are more skilful in predicting the observed SPI than the WAMI obtained from reanalysis. WAMI performance is also compared with decadal predictions from CMIP5 models based on a Sahelian precipitation index, and an improvement in predictive skill is observed in some models when WAMI is used. Therefore, we conclude that dynamics-based indices are potentially more effective for decadal prediction of precipitation in Sahel than precipitation-based indices for those models in which Sahel rainfall variability is not well simulated. We thus recommend a two-fold approach when testing the performance of models in predicting Sahel rainfall, based not only on rainfall but also on the dynamics of the West African monsoon. © 2015 Springer-Verlag Berlin Heidelberg
Montanarella L.,European Commission DG JRC |
Alva I.L.,Institute for Advanced Sustainability Studies IASS
Current Opinion in Environmental Sustainability | Year: 2015
Soils are considered across the Rio Conventions and while some advances have been made in the past two decades, implementation remains lacking and soil-related issues persist. This calls for a more integrated approach for the implementation of the Conventions. Similarly, soils will play a key role to achieve the post-2015 development agenda and can be found across the proposed Sustainable Development Goals (SDGs). This cross-cutting role is not being sufficiently acknowledged in the negotiations. Putting soils on the policy agenda will depend on a major shift in the discussion to recognize that soils underpin a wide range of services and should, therefore, be protected for future generations. Concerted efforts for advocacy within the post-2015 development agenda need to focus on keeping soils on the agenda and on making proposals for the effective implementation and monitoring of the SDGs. © 2015 Elsevier B.V.
Irvine P.J.,Institute for Advanced Sustainability Studies IASS
GAIA | Year: 2013
Solar radiation management(SRM), a subset of approaches to climate engineering, aims to manipulate the global climate on a large scale. It includes techniques like spraying sulfate aerosols into the stratosphere or brightening marine clouds to reflect more sunlight back into space. In an attempt to examine the socio-political context of SRM, research frequently starts from model projections of physi cal changes in the environment. But assessing socio-political matters is complex, and while model projections may help, experiences from research on CO2-induced climate change reveal many blind spots and some unique challenges.©2013 licensee oekom verlag.
Munoz-Anton J.,Technical University of Madrid |
Rubbia C.,Institute for Advanced Sustainability Studies IASS |
Rovira A.,Technical University of Madrid |
Martinez-Val J.M.,Technical University of Madrid
Energy Conversion and Management | Year: 2015
In this paper a systematic analysis is reported on the use of CO2 as heat carrier fluid in solar thermal receivers and as thermodynamic working fluid. It includes the performance of close-to-critical regenerative Brayton cycles, which opens a broad field of cycle possibilities with low pressure ratios (very simple turbines) complemented with large but standard heat exchangers as regenerators. Radiation intensities needed to reach relevant efficiencies are in the range above 25 kW/m2, but receiver efficiencies do not increase significantly beyond that value, featured as a threshold. Receivers are made of multi-tube bundles enclosed in glass-windowed collectors with compensated pressure and dilatation, which eliminates the problem of gas leakage through rotating joints and other non-hermetic fits. This leads to needing concentrators compatible with those collectors, which can be either finely optimized Linear Fresnel Reflectors or central minitowers. CO2 was chosen for this study because its critical temperature (31°C) is very close to environmental temperature, which conveys very positive features for the efficiency of the cycle. The overall result of the theoretical study is the identification of a set of different types of efficient, flexible and robust CSP plants with CO2 as the only fluid which deserves further research at experimental level and in the design and construction of new plant components. © 2014 Elsevier Ltd. All rights reserved.
Richter I.,Institute for Advanced Sustainability Studies IASS
Global Environment | Year: 2015
The Chesapeake Bay is the largest estuary in the United States and is home to numerous small islands. Many of these have already vanished, and those remaining are continuing to lose ground. Over a few decades several of these small places were abandoned as the waters started to roll over the lands around the midnineteenth century. Houses were torn down, while some people moved within or to other islands and others migrated to solid ground when other measures failed to secure the small islands. Some people left earlier than others, but there were moments when it became difficult to retain the society of the islands. By telling the story of the Chesapeake Islands, this paper outlines the reactions of individuals and society to changes in their living environment. The aim of the article is thereby to explore the variables influencing human thresholds to migration in times of changing environments. Societal factors, as well as natural stimuli, are explored that led to migration at a certain time and place. By drawing attention to the sinking islands in the Chesapeake, I advocate the consideration of examples from the Western Hemisphere in debates on island loss and migration. © 2015 The White Horse Press.
Zurn M.,Free University of Berlin |
Schafer S.,Institute for Advanced Sustainability Studies IASS
Global Policy | Year: 2013
Climate engineering technologies, sometimes also referred to as geoengineering technologies, attempt to ward off the worst effects of climate change by intervening in the global climate system. We see the potentials offered by climate engineering technologies in counteracting the threats of climate change but also take into account the risks that arise from the side effects of these technologies on natural, social and political systems. We find a paradox of climate engineering, which consists in the circumstance that exactly those technologies that are capable of acting fast and effectively against rising temperatures at comparatively low costs, are also the technologies that are likely to create the greatest amount of social and political conflict. To address this apparent paradox, we argue that an institutional setting for researching and potentially deploying climate engineering technologies is needed which creates a sufficiently high degree of social and political legitimacy and addresses a set of specified problems connected to climate engineering. We present a proposal for such an institutional setting that explicitly addresses these concerns. Policy Implications: • Research on and potential uses of climate engineering technologies need to be coordinated internationally in a multilateral institutional setting. • An international climate engineering agency should be created that coordinates and disseminates research on climate engineering. • Research results should be evaluated by the IPCC. • Decision-making on climate engineering should occur within the UNFCCC, where the states party to that convention should decide on norms and rules that govern climate engineering (regarding, for example, an upper limit for manipulations of the radiation balance, a uniform metric for making different responses to climate change comparable, and a time limited moratorium on field tests and deployments of climate engineering technologies). Decision-making on climate engineering should occur within the UNFCCC, where the states party to that convention should decide on norms and rules that govern climate engineering. © 2013 University of Durham and John Wiley & Sons, Ltd.
Stiem L.,Institute for Advanced Sustainability Studies IASS |
Krause T.,Lund University
International Forestry Review | Year: 2016
The Democratic Republic of Congo (DRC) with its extensive forest cover is the biggest target country for the Reducing Emissions from Deforestation and Forest Degradation (REDD+) mechanism in Africa. Despite high levels of gender inequality in rural DRC, the impacts of REDD+ interventions on gender have not been sufficiently addressed. This study examines the gender dimension at two project sites in the Equateur Province. Focus group discussions and individual interviews reveal that women spend as much time as men in the forest. Nonetheless, men's activities in the forest are often much more highly valued. This systemic devaluation of women's work, and their knowledge about the forest, legitimises men's dominance in forest governance. The results of this study finds that alongside investment in women's education, which is central for women's empowerment and their participation in forest management, local opinion leaders who shape social norms and perceptions, such as church-based organisations, are indispensable partners to make REDD+ more equitable.