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Exeter, United Kingdom

Harrison R.J.,University of Cambridge | Palin E.J.,University of Cambridge | Palin E.J.,Meteorological Office Hadley Center | Perks N.,University of Oxford
American Mineralogist | Year: 2013

Cation ordering in the magnesioferrite-qandilite (MgFe2O 4-Mg2TiO4) solid solution has been investigated using an interatomic potential model combined with Monte Carlo simulations. The dominant chemical interaction controlling the thermodynamic mixing behavior of the solid solution is a positive nearest-neighbor pairwise interaction between tetrahedrally coordinated Fe3+ and octahedrally coordinated Ti 4+ (JTFeOTi). The predicted cation distribution evolves gradually from the Néel-Chevalier model to the Akimoto model as a function of increasing JTFeOTi, with JTFeOTi = 1000 ± 100 K providing an adequate description of both the temperature and composition dependence of the cation distribution and the presence of a miscibility gap. Although Mg is a good analog of Fe2+ in end-member spinels, a comparison of model predictions for MgFe2O4-Mg2TiO4 with observed cation ordering behavior in titanomagnetite (Fe3O4-Fe 2TiO4) demonstrates that the analog breaks down for Fe3O4-rich compositions, where a value of JTFeOTi closer to zero is needed to explain the observed cation distribution. It is proposed that screening of Ti4+ by mobile charge carriers on the octahedral sublattice is responsible for the dramatic reduction in JTFeOTi. If confirmed, this conclusion will have significant implications for attempts to create a realistic thermodynamic model of titanomagnetite. Source


Willett K.M.,Meteorological Office Hadley Center | Willett K.M.,University of East Anglia | Jones P.D.,University of East Anglia | Thorne P.W.,Meteorological Office Hadley Center | And 3 more authors.
Environmental Research Letters | Year: 2010

Observed changes in the HadCRUH global land surface specific humidity and CRUTEM3 surface temperature from 1973 to 1999 are compared to CMIP3 archive climate model simulations with 20th Century forcings. Observed humidity increases are proportionately largest in the Northern Hemisphere, especially in winter. At the largest spatio-temporal scales moistening is close to the Clausius-Clapeyron scaling of the saturated specific humidity (∼7% K -1). At smaller scales in water-limited regions, changes in specific humidity are strongly inversely correlated with total changes in temperature. Conversely, in some regions increases are faster than implied by the Clausius-Clapeyron relation. The range of climate model specific humidity seasonal climatology and variance encompasses the observations. The models also reproduce the magnitude of observed interannual variance over all large regions. Observed and modelled trends and temperature-humidity relationships are comparable except for the extratropical Southern Hemisphere where observations exhibit no trend but models exhibit moistening. This may arise from: long-term biases remaining in the observations; the relative paucity of observational coverage; or common model errors. The overall degree of consistency of anthropogenically forced models with the observations is further evidence for anthropogenic influence on the climate of the late 20th century. © 2010 IOP Publishing Ltd. Source


Parham P.E.,University of Liverpool | Parham P.E.,Imperial College London | Waldock J.,The Cyprus Institute | Waldock J.,Imperial College London | And 16 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2015

Arguably one of the most important effects of climate change is the potential impact on human health. While this is likely to take many forms, the implications for future transmission of vector-borne diseases (VBDs), given their ongoing contribution to global disease burden, are both extremely important and highly uncertain. In part, this is owing not only to data limitations and methodological challenges when integrating climate-driven VBD models and climate change projections, but also, perhaps most crucially, to the multitude of epidemiological, ecological and socio-economic factors that drive VBD transmission, and this complexity has generated considerable debate over the past 10–15 years. In this review, we seek to elucidate current knowledge around this topic, identify key themes and uncertainties, evaluate ongoing challenges and open research questions and, crucially, offer some solutions for the field. Although many of these challenges are ubiquitous across multiple VBDs, more specific issues also arise in different vector–pathogen systems. © 2015 The Author(s) Published by the Royal Society. All rights reserved. Source

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