Why radiative forcing might fail as a predictor of climate change

Radiative forcing has been widely used as a metric of climate change, i.e. as a measure by which various contributors to a net surface temperature change can be quantitatively compared. The extent to which this concept is valid for spatially inhomogeneous perturbations to the climate system is tested. A series of climate model simulations involving ozone changes of different spatial structure reveals that the climate sensitivity parameter is highly variable: for an ozone increase in the northern hemisphere lower stratosphere, it is more than twice as large as for a homogeneous CO₂ perturbation. A global ozone perturbation in the upper troposphere, however, causes a significantly smaller surface temperature response than CO₂. The variability of the climate sensitivity parameter is shown to be mostly due to the varying strength of the stratospheric water vapour feedback. The variability of the sea-ice albedo feedback modifies climate sensitivity of perturbations with the same vertical structure but a different horizontal structure. This feedback is also the origin of the comparatively larger climate sensitivity to perturbations restricted to the northern hemisphere extratropics. As cloud feedback does not operate independently from the other feedbacks, quantifying its effect is rather difficult. However, its effect on the variability of for horizontally and vertically inhomogeneous perturbations within one model framework seems to be comparatively small.This revised version was published online March 2005 with corrections to table 5.     

Flow recession as a driver of the morpho‐texture of braided streams

Braiding has been widely studied in humid‐temperate climates though rarely in arid environments. Morpho‐texture of braided streams refers to the morphological‐textural organization in a braid‐cell (stream section including bars, anabranches and chutes) that may strongly relate to different processes and hydrological regimes. The objective of this study is to compare the morpho‐texture of braided streams governed by diverse flow recessions in different climates. Measurements were conducted in the wadis Ze'elim and Rahaf, southeast hyper‐arid Israel, in the Mediterranean Barranca‐de‐los‐Pinos, central Spain and in humid‐temperate braided systems, the La‐Bléone River, Haute‐Provence, France and in the Saisera and Cimoliana torrents, northeast Italy. Terrestrial laser scanning was used to produce point clouds and high resolution digital elevation models of the braid‐cells. Wet braid‐cells in humid‐temperate environments were surveyed by a Total Station. Roughness and the upper tail of grain size distributions were derived from the scanned point clouds or from Wolman sampling. We found that anabranches are commonly finer‐grained than the bars in dryland systems and in semi‐arid sandy braided systems, contrary to the humid‐temperate braided systems. In both climates, chutes are similar or coarser‐grained than the bars which they dissect, in accordance with their steeper gradients due to the considerable bar‐anabranch relief. The Saisera's morpho‐texture is similar to that of the dryland braided channels, despite the very humid‐temperate environment in which it is located, due to its short‐lived, ephemeral type hydrograph. Hydrograph shape, specifically the duration of flow recession, typical of a climate but not confined to it, determines the morpho‐texture of braided streams and the textural differentiation between a depositional bar and the adjacent anabranches. The morpho‐texture of chutes and bars results also from local erosional processes affected by local topography, i.e. ungraded longitudinal profiles, and is not solely determined by flow recession. This new morpho‐textural model enables identifying primary depositional and erosional braiding processes. Copyright © 2015 John Wiley & Sons, Ltd.     

Early Ipswichian (last interglacial) sea level rise in the channel region: Stone Point Site of Special Scientific Interest,Hampshire, England

Constraining the speed of sea level rise at the start of an interglacial is important to understanding the size of the ‘window of opportunity’ available for hominin migration. This is particularly important during the last interglacial when there is no evidence for significant hominin occupation anywhere in Britain. There are very few finer grained fossiliferous sequences in the Channel region that can be used to constrain sea level rise and they are preserved only to the north of the Channel, in England. Of these, the sequence at Stone Point SSSI is by far the most complete. Data from this sequence has been previously reported, and discussed at a Quaternary Research Association Field Meeting, where a number of further questions were raised that necessitated further data generation. In this paper, we report new data from this sequence – thin section analysis, isotopic determinations on ostracod shells, new Optical Stimulated Luminescence ages and Amino Acid Recem analyses. These show early sea level rise in this sequence, starting during the pre-temperate vegetation zone IpI, but no early warming. The implications of this almost certainly last interglacial sequence for the human colonisation of Britain and our understanding of the stratigraphic relationship of interglacial estuarine deposits with their related fluvial terrace sequences is explored.     

Role of Humification Processes in Recycling Organic Wastes of Various Nature and Sources as Soil Amendments

Recycling the large amounts of organic wastes produced by agriculture, forestry, urban and industrial activities as soil, organic amendments are the most popular and efficient option for avoiding their dispersion in the environment and restoring, maintaining, and/or improving the content of soil organic matter. Chemical stability and biological maturity are two important factors for the successful use of organic wastes in agriculture with limited risk for the surrounding environment. Stabilization and maturation of raw organic wastes inherently imply the achievement of an extensive humification, that is, a wide conversion of easily degradable organic matter to refractory organic compounds that resemble native soil humic substances (HS). Soil HS are the most important components of soil organic matter responsible of several soil functions and processes. As a consequence, the amount and quality of HS‐like fractions in any organic amendment are believed to be of primary importance for its agronomic efficacy, environmental safety and economic value. The first part of this review focuses on the chemical and physico‐chemical changes occurring in the humic substances (HS) ‐like fractions of organic wastes of various nature and sources subjected to common treatment processes aimed at producing environmentally‐safe soil amendments with beneficial agronomic properties. The second part discusses the composition, structure, and chemical reactivity of the HS‐like components in organic amendments of various origins and nature, and their effects on native soil HS. The review concludes by highlighting the need for innovative research targeted mainly to achieve a better fundamental understanding of the molecular structure and reactivity of soil HS and HS‐like fractions in organic amendments, the mechanisms of HS formation and transformations in the natural environment and during the treatment processes of raw organic wastes, the interactions with metals and organic xenobiotics, and the direct physiological effects that HS may exert on plants.     

Moisture budget variations in the Yangtze River Basin, China, and possible associations with large-scale circulation

We analyzed seasonal and annual variations of the whole layer atmospheric moisture budget and precipitation during 1961–2005 and their associations with large-scale circulation in the Yangtze River basin, China. The results indicated increasing moisture budget in summer and winter, but decreasing moisture budget in spring and autumn. Positive correlations between moisture budget and precipitation illustrate tremendous impacts the moisture budget has on the precipitation changes across the Yangtze River basin. In terms of seasonal variations, significant correlations were observed between precipitation and moisture budget in spring and autumn in the upper Yangtze River basin. Besides, we also analyzed changes of geopotential height. The positive trends of the geopotential height (850 hPa) were observed in the East Asia and the negative trends in the middle and west Pacific Ocean, indicating increasing geopotential height from south to north in east Asia which largely limited the moisture propagation to north China. While decreasing meridional geopotential height from west to east along the Yangtze River basin caused more moisture propagation from the west to the east parts of the study region, which may benefit more precipitation in the middle and lower Yangtze River basin.     

An operational model to estimate hourly and daily crop evapotranspiration in hilly terrain: validation on wheat and oat crops

In this paper, we present an operational model to estimate the actual evapotranspiration (ET) of crops cultivated on hilly terrains. This new model has the following three characteristics: (1) ET modelling is based on a Penman?CMonteith (PM) type equation (Monteith 1965) where canopy resistance is simulated by following an approach already illustrated by Katerji and Perrier (Agronomie 3(6):513?C521, 1983); (2) the estimation of ET, by means of the PM equation, is made by using meteorological variables simulated on sloped sites as input; (3) these variables are simulated by using simple relationships linking the variables measured at a reference site on plane to the topographic characteristics of the site (slope, orientation, altitude as difference between reference, and sloped sites). This approach presents two advantages if compared with previously proposed models: Not only computation steps are greatly simplified but also error sources due to the simulation of climatic variables in sloped sites and the ET estimation are well distinguished. This model was validated at hourly and daily scales at four sites cultivated with wheat and oats offering a wide range of slope and orientation values: a reference site on plane, site 1 (9° sloping, NW orientation, 7 m from the reference site in plane), site 2 (6°, SE, 12 m) and site 3 (1°, SE, 18 m). At hourly scale, the new model performed well at all sites studied. The observed slope of the linear relationships between estimated and measured ET values ranged between 0.93 and 1.03, with coefficients of determination, r ², between 0.80 and 0.98. At daily scale, the slopes of the linear relationships between measured and estimated ET for the sites on plane and the sloped sites were practically the same (0.98?±?0.01); however, the coefficient of determination r ² observed in the site on plane was clearly greater (0.98) than that observed in the sloped sites (0.83). The presented analysis does not show any significant systematic effect of topography (slope and orientation of the plots) on the good performance of the proposed model for the ET estimation. Furthermore, we observed that coefficients of determination tend to decrease with the increase in the slope of the site, which translates into increased inaccuracy of the climatic variables simulation, in particular the net radiation, as the slope of the site increases. The proposed model allows to verify the different steps for calculating the fluxes, to identify the eventual sources of error and to make the needed corrections. For this reasons, the proposed model seems to be particularly ??operational??, i.e. a useful tool for estimating fluxes on hilly terrains.     

Phytoremediation of Pyrene Contaminated Soils by Different Plant Species

Polycyclic aromatic hydrocarbons (PAHs) present serious problems in the environment because they may affect negatively human health and alter native ecological communities. Phytoremediation has long been recognized as an efficient method of eliminating PAH pollutants from soil. A pot experiment was conducted in greenhouse conditions to investigate the capability of three plant species, Medicago sativa, Brassica napus, and Lolium perenne, to promote the degradation of pyrene by measuring their growth on pyrene‐contaminated soils. After 90 days, pyrene concentration in soils declined by 32, 30, and 28%, respectively, with M. sativa, B. napus, and L. perenne, whereas it decreased only by 18% in the control soil without plants. These results indicated that pyrene was successfully removed by plants used. In particular, M. sativa showed the highest capacity for pyrene dissipation in soil, whereas L. perenne was more efficient in limiting adverse effects of pyrene contamination. In addition, the contaminant pyrene was undetectable in shoots and roots of the three species, likely because plant roots can stimulate soil microbial biomass and oxygen transport to the rhizosphere, thus facilitating indirectly the degradation process of pyrene. Further studies are in progress to evaluate the possible adsorption of pyrene to soil organic matter.     

Environmental impact of the MV CITA on the foreshore of Porth Hellick, Isles of Scilly

The grounding of the container feeder vessel MV CITA on Newfoundland Rocks, Isles of Scilly, had an effect on the surrounding biota and benthic environment. Included in the CITA's cargo were five 40 ft containers holding pallets of polyester film used in the production of audio and visual recording tapes. The wreckage presented a minor but potentially chronic source of pollution through the delayed release of polythene film, which was left on the seabed as it was considered insufficiently valuable to warrant salvage. The polythene disintegrated and was washed upon the foreshore of Porth Hellick in minute shreds. The adjacent foreshore and two control sites within the islands were analysed using a 5-strand line and vegetation survey with 10 random quadrats within each line to determine the environmental impact of the polythene.