Climatic impacts of stratospheric geoengineering with sulfate, black carbon and titania injection

In this paper, we examine the potential climatic effects of geoengineering by sulfate, black carbon and titania injection against a baseline RCP8.5 scenario. We use the HadGEM2-CCS model to simulate scenarios in which the top-of-the-atmosphere radiative imbalance due to rising greenhouse gas concentrations is offset by sufficient aerosol injection throughout the 2020–2100 period. We find that the global-mean temperature is effectively maintained at historical levels for the entirety of the period for all 3 aerosol-injection scenarios, though there are a wide range of side-effects which are discussed in detail. The most prominent conclusion is that although the BC injection rate necessary to produce an equivalent global mean temperature-response is much lower, the severity of stratospheric temperature changes (> +70 °C) and precipitation impacts effectively exclude BC from being a viable option for geoengineering. Additionally, while it has been suggested that titania would be an effective particle because of its high scattering efficiency, it also efficiently absorbs solar ultraviolet radiation producing a significant stratospheric warming (> +20 °C). As injection rates for titania are close to those for sulfate, there appears little benefit of using titania when compared to injection of sulfur dioxide, which has the added benefit of being well modelled through extensive research that has been carried out on naturally occurring explosive volcanic eruptions.The authors would like to thank Valentina Aquila for supplying AVHRR and SAGE data, and to Peter Cox, Angus Ferraro, David Keith and Alan Robock for helpful discussions. A. C. Jones was supported by a Met Office/NERC CASE (ref. 580 009 183) PhD studentship; J. M. Haywood and A. Jones were supported by the Joint UK DECC/Defra Met Office Hadley Centre Climate Programme (GA01101)

Sensitivity of volcanic aerosol dispersion to meteorological conditions: A Pinatubo case study

This is the final version of the article. Available from American Geophysical Union via the DOI in this record.Using a global climate model (Hadley Centre Global Environment Model version 2-Carbon Cycle Stratosphere ) with a well-resolved stratosphere, we test the sensitivity of volcanic aerosol plume dispersion to meteorological conditions by simulating 1 day Mount Pinatubo-like eruptions on 10 consecutive days. The dispersion of the volcanic aerosol is found to be highly sensitive to the ambient meteorology for low-altitude eruptions (16–18 km), with this variability related to anomalous anticyclonic activity along the subtropical jet, which affects the permeability of the tropical pipe and controls the amount of aerosol that is retained by the tropical reservoir. Conversely, a high-altitude eruption scenario (19–29 km) exhibits low meteorological variability. Overcoming day-to-day meteorological variability by spreading the emission over 10 days is shown to produce insufficient radiative heating to loft the aerosol into the stratospheric tropical aerosol reservoir for the low eruption scenario. This results in limited penetration of aerosol into the southern hemisphere (SH) in contrast to the SH transport observed after the Pinatubo eruption. Our results have direct implications for the accurate simulation of past/future volcanic eruptions and volcanically forced climate changes, such as Intertropical Convergence Zone displacement.A.C.J. was funded by a NERC/CASE PhD studentship (ref. 580 009 138, with CASE partner being the Met Office); J.M.H. and A.J. were supported by the Joint UK DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). The authors would like to thank Larry Thomason for supplying the SAGE II data. Data are freely available by contacting A.C.J

Modelling the failure precursor mechanism of lamellar fibrous tissues, example of the annulus fibrosus

The aims of this study were to assess the damage and failure strengths of lamellar fibrous tissues, such as the anterior annulus fibrosus (AF), and to develop a mathematical model of damage propagation of the lamellae and inter-lamellar connections. This level of modelling is needed to accurately predict the effect of damage and failure induced by trauma or clinical interventions. 26 ovine anterior AF cuboid specimens from 11 lumbar intervertebral discs were tested in radial tension and mechanical parameters defining damage and failure were extracted from the in-vitro data. Equivalent 1D analytical models were developed to represent the specimen strength and the damage propagation, accounting for the specimen dimensions and number of lamellae. Model parameters were calibrated on the in-vitro data. Similar to stiffness values reported for other orientations, the outer annulus was found stronger than the inner annulus in the radial direction, with failure at higher stress values. The inner annulus failed more progressively, showing macroscopic failure at a higher strain value. The 1D analytical model of damage showed that lamellar damage is predominant in the failure mechanism of the AF. The analytical model of the connections between lamellae allowed us to represent separately damage processes in the lamellae and the inter-lamellar connections, which cannot be experimentally tested individually

Optimizing computational methods of modeling vertebroplasty in experimentally augmented human lumbar vertebrae

Vertebroplasty has been widely used for the treatment of osteoporotic compression fractures but the efficacy of the technique has been questioned by the outcomes of randomized clinical trials. Finite‐element (FE) models allow an investigation into the structural and geometric variation that affect the response to augmentation. However, current specimen‐specific FE models are limited due to their poor reproduction of cement augmentation behavior. The aims of this study were to develop new methods of modeling the vertebral body in both a nonaugmented and augmented state. Experimental tests were conducted using human lumbar spine vertebral specimens. These tests included micro‐computed tomography imaging, mechanical testing, augmentation with cement, reimaging, and retesting. Specimen‐specific FE models of the vertebrae were made comparing different approaches to capturing the bone material properties and to modeling the cement augmentation region. These methods significantly improved the modeling accuracy of nonaugmented vertebrae. Methods that used the registration of multiple images (pre‐ and post‐augmentation) of a vertebra achieved good agreement between augmented models and their experimental counterparts in terms of predictions of stiffness. Such models allow for further investigation into how vertebral variation influences the mechanical outcomes of vertebroplasty

Southern Ocean albedo, inter-hemispheric energy transports and the double ITCZ: global impacts of biases in a coupled model

A causal link has been invoked between inter-hemispheric albedo, cross-equatorial energy transport and the double-IntertropicalConvergence Zone (ITCZ) bias in climate models. Southern Ocean cloud biases are a major determinant of inter-hemispheric albedo biases in many models, including HadGEM2-ES, a fully coupled model with a dynamical ocean. In this study, targeted albedo corrections are applied to explore the dynamical response to artificially reducing these biases. The Southern Hemisphere jet increases in strength in response to the increased tropical-extratropical temperature gradient, with increased energy transport into the mid-latitudes in the atmosphere, but no improvement is observed in the double-ITCZ bias or atmospheric cross-equatorial energy transport. The majority of the adjustment in energy transport in the tropics is achieved in the ocean, with the response further limited to the Pacific Ocean. As a result, the frequently argued teleconnection between the Southern Ocean and tropical precipitation biases is muted. Further experiments in which tropical longwave biases are also reduced do not yield improvement in the representation of the tropical atmosphere. These results suggest that the dramatic improvements in tropical precipitation that have been shown in previous studies may be a function of the lack of dynamical ocean and/or the simplified hemispheric albedo bias corrections applied in that work. It further suggests that efforts to correct the double ITCZ problem in coupled models that focus on large-scale energetic controls will prove fruitless without improvements in the representation of atmospheric processes.MKH, MC and JMH were supported by the Natural Environment Research Council/Department for International Development via the Future Climates for Africa (FCFA) funded project ’Improving Model Processes for African Climate’ (IMPALA, NE/M017265/1). JMH and AJ were supported by the Joint UK DECC/Defra Met Office Hadley Centre Climate Programme (GA01101)

Robust Buchwald-Hartwig amination enabled by ball-milling

An operationally simple mechanochemical method for the Pd catalysed Buchwald–Hartwig amination of arylhalides with secondary amines has been developed using a Pd PEPPSI catalyst system. The system is demonstrated on 30 substrates and applied in the context of a target synthesis. Furthermore, the performance of the reaction under aerobic conditions has been probed under traditional solution and mechanochemical conditions, the observations are discussed herein