Temperature and precipitation effects on wheat yield across a European transect: a crop model ensemble analysis using impact response surfaces

This study explored the utility of the impact response surface (IRS) approach for investigating model ensemble crop yield responses under a large range of changes in climate. IRSs of spring and winter wheat Triticum aestivum yields were constructed from a 26-member ensemble of process-based crop simulation models for sites in Finland, Germany and Spain across a latitudinal transect. The sensitivity of modelled yield to systematic increments of changes in temperature (-2 to +9°C) and precipitation (-50 to +50%) was tested by modifying values of baseline (1981 to 2010) daily weather, with CO2 concentration fixed at 360 ppm. The IRS approach offers an effective method of portraying model behaviour under changing climate as well as advantages for analysing, comparing and presenting results from multi-model ensemble simulations. Though individual model behaviour occasionally departed markedly from the average, ensemble median responses across sites and crop varieties indicated that yields decline with higher temperatures and decreased precipitation and increase with higher precipitation. Across the uncertainty ranges defined for the IRSs, yields were more sensitive to temperature than precipitation changes at the Finnish site while sensitivities were mixed at the German and Spanish sites. Precipitation effects diminished under higher temperature changes. While the bivariate and multi-model characteristics of the analysis impose some limits to interpretation, the IRS approach nonetheless provides additional insights into sensitivities to inter-model and inter-annual variability. Taken together, these sensitivities may help to pinpoint processes such as heat stress, vernalisation or drought effects requiring refinement in future model development.

Desert dust suppressing precipitation: A possible desertification feedback loop

The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process.

Multidecadal variability of the continental precipitation annual amplitude driven by AMO and ENSO

As the water vapor content in the atmosphere scales with temperature, a warmer world is expected to feature an intensification of the hydrological cycle. Work to date has mainly focused on mean precipitation changes, whose connection to climatic modes is elusive at a global scale. Here we show that continental precipitation annual amplitude, which represents the annual range between minimum and maximum (monthly) rainfall, covaries with a linear combination of the Atlantic Multidecadal Oscillation and low-frequency variations in the El Niño–Southern Oscillation on a decadal to multidecadal scale with a correlation coefficient of 0.92 (P<0.01). The teleconnection is a result of changes in moisture transport in key regions. Reported trends in the annual amplitude of global precipitation in recent decades need to be assessed in light of this substantial low-frequency variability, which could mask or enhance an anthropogenic signal in hydrological cycle changes.

Synthesis of Robust Hierarchical Silica Monoliths by Surface-Mediated Solution/Precipitation Reactions over Different Scales: Designing Capillary Microreactors for Environmental Applications

A synthetic procedure to prepare novel materials (surface-mediated fillings) based on robust hierarchical monoliths is reported. The methodology includes the deposition of a (micro- or mesoporous) silica thin film on the support followed by growth of a porous monolithic SiO2 structure. It has been demonstrated that this synthesis is viable for supports of different chemical nature with different inner diameters without shrinkage of the silica filling. The formation mechanism of the surface-mediated fillings is based on a solution/precipitation process and the anchoring of the silica filling to the deposited thin film. The interaction between the two SiO2 structures (monolith and thin film) depends on the porosity of the thin film and yields composite materials with different mechanical stability. By this procedure, capillary microreactors have been prepared and have been proved to be highly active and selective in the total and preferential oxidation of carbon monoxide (TOxCO and PrOxCO).

Pollen abundances, and temperature and precipitation reconstruction for the Eocene to Oligocene transition in northern high latitudes

A profound global climate shift took place at the Eocene-Oligocene transition (~33.5 million years ago) when Cretaceous/early Palaeogene greenhouse conditions gave way to icehouse conditions (Zachos et al., 2001, doi:10.1126/science.1059412; Coxall et al., 2005, doi:10.1038/nature03135; Lear et al., 2008, doi:10.1130/G24584A.1). During this interval, changes in the Earth's orbit and a long-term drop in atmospheric carbon dioxide concentrations (Pagani et al., 2005, doi:10.1126/science.1110063; Pearson and Palmer, 2000, doi:10.1038/35021000; DeConto and Pollard, 2003, doi:10.1038/nature01290) resulted in both the growth of Antarctic ice sheets to approximately their modern size (Coxall et al., 2005, doi:10.1038/nature03135; Lear et al., 2008, doi:10.1130/G24584A.1) and the appearance of Northern Hemisphere glacial ice (Eldrett et al., 2007, doi:10.1038/nature05591; Moran et al., 2006, doi:10.1038/nature04800). However, palaeoclimatic studies of this interval are contradictory: although some analyses indicate no major climatic changes (Kohn et al., 2004, doi:10.1130/G20442.1; Grimes et al., 2005, doi:10.1130/G21019.1), others imply cooler temperatures (Zanazzi et al., 2007, doi:10.1038/nature05551), increased seasonality (Ivany et al., 2000, doi:10.1038/35038044; Terry, 2001, doi:10.1016/S0031-0182(00)00248-0) and/or aridity (Ivany et al., 2000, doi:10.1038/35038044; Terry, 2001, doi:10.1016/S0031-0182(00)00248-0; Sheldon et al., 2002, doi:10.1086/342865; Dupont-Nivet et al., 2007, doi:10.1038/nature05516). Climatic conditions in high northern latitudes over this interval are particularly poorly known. Here we present northern high-latitude terrestrial climate estimates for the Eocene to Oligocene interval, based on bioclimatic analysis of terrestrially derived spore and pollen assemblages preserved in marine sediments from the Norwegian-Greenland Sea. Our data indicate a cooling of ~5 °C in cold-month (winter) mean temperatures to 0-2 °C, and a concomitant increased seasonality before the Oi-1 glaciation event. These data indicate that a cooling component is indeed incorporated in the d18O isotope shift across the Eocene-Oligocene transition. However, the relatively warm summer temperatures at that time mean that continental ice on East Greenland was probably restricted to alpine outlet glaciers.

Barium isotope fractionation during witherite (BaCO3) dissolution, precipitation and at equilibrium

This study examines the behavior of Ba isotope fractionation between witherite and fluid during mineral dissolution, precipitation and at chemical equilibrium. Experiments were performed in batch reactors at 25 oC in 10-2 M NaCl solution where the pH was adjusted by continuous bubbling of a water saturated gas phase of CO2 or atmospheric air. During witherite dissolution no Ba isotope fractionation was observed between solid and fluid. In contrast, during witherite precipitation, caused by a pH increase, a preferential uptake of the lighter 134Ba isotopomer in the solid phase was observed. In this case, the isotope fractionation factor αwitherite-fluid is calculated to be 0.99993 ± 0.00004 (or Δ137/134Bawitherite-fluid ≈ -0.07 ± 0.04 ‰, 2sd). The most interesting feature of this study, however, is that after the attainment of chemical equilibrium, the Ba isotope composition of the aqueous phase is progressively becoming lighter, indicating a continuous exchange of Ba2+ ions between witherite and fluid. Mass balance calculations indicate that the detachment of Ba from the solid is not only restricted to the outer surface layer of the solid, but affects several (~7 unit cells) subsurface layers of the crystal. This observation comes in excellent agreement with the concept of a dynamic system at chemical equilibrium in a mineral-fluid system, denoting that the time required for the achievement of isotopic equilibrium in the witherite-fluid system is longer compared to that observed for chemical equilibrium. Overall, these results indicate that the isotopic composition of Ba bearing carbonates in natural environments may be altered due to changes in fluid composition without a net dissolution/precipitation to be observed.

Sensitivity of soil regions to acid precipitation /

Mode of access: Internet.

Effects of acid precipitation on soil leachate quality : computer calculations /

Mode of access: Internet.

Inputs of phosphorus from precipitation to Lake Michigan /

"Grant No. 802647."

Precipitation and inactivation of phosphorus as a lake restoration technique /

Mode of access: Internet.

Precipitation of the sulphides of nickel & cobalt in an alkaline tartrate solution : together with an investigation into the nature of certain tartrates of these metals.

Reprinted from the Journal of the American chemical society, v. 22, no. 8, Ag. 1900.