The Aqua-Planet Experiment (APE): CONTROL SST Simulation

Climate simulations by 16 atmospheric general circulation models (AGCMs) are compared on an aqua-planet, a water-covered Earth with prescribed sea surface temperature varying only in latitude. The idealised configuration is designed to expose differences in the circulation simulated by different models. Basic features of the aqua-planet climate are characterised by comparison with Earth. The models display a wide range of behaviour. The balanced component of the tropospheric mean flow, and mid-latitude eddy covariances subject to budget constraints, vary relatively little among the models. In contrast, differences in damping in the dynamical core strongly influence transient eddy amplitudes. Historical uncertainty in modelled lower stratospheric temperatures persists in APE. Aspects of the circulation generated more directly by interactions between the resolved fluid dynamics and parameterized moist processes vary greatly. The tropical Hadley circulation forms either a single or double inter-tropical convergence zone (ITCZ) at the equator, with large variations in mean precipitation. The equatorial wave spectrum shows a wide range of precipitation intensity and propagation characteristics. Kelvin mode-like eastward propagation with remarkably constant phase speed dominates in most models. Westward propagation, less dispersive than the equatorial Rossby modes, dominates in a few models or occurs within an eastward propagating envelope in others. The mean structure of the ITCZ is related to precipitation variability, consistent with previous studies. The aqua-planet global energy balance is unknown but the models produce a surprisingly large range of top of atmosphere global net flux, dominated by differences in shortwave reflection by clouds. A number of newly developed models, not optimised for Earth climate, contribute to this. Possible reasons for differences in the optimised models are discussed. The aqua-planet configuration is intended as one component of an experimental hierarchy used to evaluate AGCMs. This comparison does suggest that the range of model behaviour could be better understood and reduced in conjunction with Earth climate simulations. Controlled experimentation is required to explore individual model behaviour and investigate convergence of the aqua-planet climate with increasing resolution.

Exploring the market potential of 'local' in food systems

Local food initiatives create a niche market in many developed countries where consumer choice is being met with an expanding offering in both conventional as well as complementary retail outlets. Supermarkets in conjunction with the food service sector currently dominate food sales and consumption, and are likely to do so for the foreseeable future. However, the local food sector offers an opportunity for implementing niche marketing strategies for many businesses. Local food activities tend to be relatively independent activities and a clearer definition for “local” food would assist in consolidating this important component of the food system. Related to this, consumers would benefit from the establishment of some form of assurance system for the ‘localness’ of food. In the UK, with its well established local food market, farmers’ markets, farm shops and box schemes are currently having the largest impact in terms of total sales. Hence further research is required to confirm that support for similar business ventures in Australia would be a viable strategy for strengthening its local food systems.

Effect of triclosan or a phenolic farm disinfectant on the selection of antibiotic-resistant Salmonella enterica

Objective: To determine the effect of growth of five strains of Salmonella enterica and their isogenic multiply antibiotic-resistant (MAR) derivatives with a phenolic farm disinfectant or triclosan (biocides) upon the frequency of mutation to resistance to antibiotics or cyclohexane. Methods: Strains were grown in broth with or without the biocides and then spread on to agar containing ampicillin, ciprofloxacin or tetracycline each at 4x MIC or agar overlaid with cyclohexane. Incubation was for 24 and 48 h and the frequency of mutation to resistance was calculated for strains with and without prior growth with the biocides. MICs were determined and the presence of mutations in the acrR and marR regions was determined by sequencing and the presence of mutations in gyrA by light-cycler analysis, for a selection of the mutants that arose. Results: The mean frequency of mutation to antibiotic or cyclohexane resistance was increased similar to10- to 100-fold by prior growth with the phenolic disinfectant or triclosan. The increases were statistically significant for all antibiotics and cyclohexane following exposure to the phenolic disinfectant (P less than or equal to 0.013), and for ampicillin and cyclohexane following exposure to triclosan (P less than or equal to 0.009). Mutants inhibited by >1 mg/L ciprofloxacin arose only from strains that were MAR. Reduced susceptibility to ciprofloxacin (at 4x MIC for parent strains) alone was associated with mutations in gyrA. MAR mutants did not contain mutations in the acrR or marR region. Conclusions: These data renew fears that the use of biocides may lead to an increased selective pressure towards antibiotic resistance.

Farm disinfectants select for cyclohexane resistance, a marker of multiple antibiotic resistance, in Escherichia coli

Aims: The aim of this study was to determine if three classes of farm disinfectants were able to select for ciprofloxacin or cyclohexane tolerant [ indicative of a multiple antibiotic resistance ( MAR) phenotype] Escherichia coli and if cyclohexane-tolerant E. coli could be isolated from farms. Methods and Results: Chicken slurry containing ca 1 : 99 ratio ciprofloxacin resistant : susceptible E. coli ( 10 different resistant strains examined) was treated for 24 h with each of the disinfectants and examined for survival of resistant : susceptible strains. Ciprofloxacin-sensitive ( n = 5) and - resistant ( n = 5) E. coli were grown with sublethal concentrations of the disinfectants and then plated to agar containing ciprofloxacin or overlaid with cyclohexane. Escherichia coli ( n = 389) isolated from farms were tested for cyclohexane tolerance. Minimum inhibitory concentrations ( MIC) were determined against representative isolates and mutants. The disinfectants did not select for the ciprofloxacin-resistant E. coli in poultry slurry but following growth with each of the three disinfectants, higher numbers ( Pless than or equal to 0(.)023) of cyclohexane-tolerant E. coli were isolated and these had a MAR phenotype. Of the 389 farm E. coli tested, only one was cyclohexane tolerant. Conclusions: It is possible that in a farm environment, E. coli could be exposed to similar concentrations of the disinfectants that are selected for MAR type organisms under these laboratory conditions. Significance and Impact of the Study: Data from this study suggest that cyclohexane-resistant E. coli are not common on farms, but in view of the ease of isolating them in the laboratory with farm disinfectants, further investigations on farms are warranted.

Commonly used farm disinfectants can select for mutant Salmonella enterica serovar Typhimurium with decreased susceptibility to biocides and antibiotics without compromising virulence

Objectives: To determine if one passage of Salmonella enterica serovar Typhimurium in the presence of farm disinfectants selected for mutants with decreased susceptibility to disinfectants and/or antibiotics. Methods: Eight Salmonella Typhimurium strains including field isolates and laboratory mutants were exposed to either a tar oil phenol (PFD) disinfectant, an oxidizing compound disinfectant (OXC), an aldehyde based disinfectant (ABD) or a dairy sterilizer disinfectant (based on quaternary ammonium biocide) in agar. The susceptibility of mutants obtained after disinfectant exposure to antibiotics and disinfectants was determined as was the accumulation of norfloxacin. The proteome of SL1344 after exposure to PFD and OXC was analysed using two-dimensional liquid chromatography mass spectrometry. Results: Strains with either acrB or tolC inactivated were more susceptible to most disinfectants than other strains. The majority (3/5) of mutants recovered after disinfectant exposure required statistically significantly longer exposure times to disinfectants than their parent strains to generate a 5 log kill. Small decreases in antibiotic susceptibility were observed but no mutants were multiply antibiotic-resistant (MAR). Notably exposure to ABD decreased susceptibility to ciprofloxacin in some strains. Mutants with increased disinfectant tolerance were able to survive and persist in chicks as well as in parent strains. Analysis of proteomes revealed significantly increased expression of the AcrAB-TolC efflux system after PFD exposure. Conclusions: Data presented demonstrate that efflux pumps are required for intrinsic resistance to some disinfectants and that exposure to disinfectants can induce expression of the AcrAB-TolC efflux system, but that single exposure was insufficient to select for MAR strains.

When do export subsidies have a redistributional role? Reply

Our differences are three. The first arises from the belief that "... a nonzero value for the optimally chosen policy instrument implies that the instrument is efficient for redistribution" (Alston, Smith, and Vercammen, p. 543, paragraph 3). Consider the two equations: (1) o* = f(P3) and (2) = -f(3) ++r h* (a, P3) representing the solution to the problem of maximizing weighted, Marshallian surplus using, simultaneously, a per-unit border intervention, 9, and a per-unit domestic intervention, wr. In the solution, parameter ot denotes the weight applied to producer surplus; parameter p denotes the weight applied to government revenues; consumer surplus is implicitly weighted one; and the country in question is small in the sense that it is unable to affect world price by any of its domestic adjustments (see the Appendix). Details of the forms of the functions f((P) and h(ot, p) are easily derived, but what matters in the context of Alston, Smith, and Vercammen's Comment is: Redistributivep referencest hatf avorp roducers are consistent with higher values "alpha," and whereas the optimal domestic intervention, 7r*, has both "alpha and beta effects," the optimal border intervention, r*, has only a "beta effect,"-it does not have a redistributional role. Garth Holloway is reader in agricultural economics and statistics, Department of Agricultural and Food Economics, School of Agriculture, Policy, and Development, University of Reading. The author is very grateful to Xavier Irz, Bhavani Shankar, Chittur Srinivasan, Colin Thirtle, and Richard Tiffin for their comments and their wisdom; and to Mario Mazzochi, Marinos Tsigas, and Cal Turvey for their scholarship, including help in tracking down a fairly complete collection of the papers that cite Alston and Hurd. They are not responsible for any errors or omissions. Note, in equation (1), that the border intervention is positive whenever a distortion exists because 8 > 0 implies 3 - 1 + 8 > 1 and, thus, f((P) > 0 (see Appendix). Using Alston, Smith, and Vercammen's definition, the instrument is now "efficient," and therefore has a redistributive role. But now, suppose that the distortion is removed so that 3 - 1 + 8 = 1, 8 = 0, and consequently the border intervention is zero. According to Alston, Smith, and Vercammen, the instrument is now "inefficient" and has no redistributive role. The reader will note that this thought experiment has said nothing about supporting farm incomes, and so has nothing whatsoever to do with efficient redistribution. Of course, the definition is false. It follows that a domestic distortion arising from the "excess-burden argument" 3 = 1 + 8, 8 > 0 does not make an export subsidy "efficient." The export subsidy, having only a "beta effect," does not have a redistributional role. The second disagreement emerges from the comment that Holloway "... uses an idiosyncratic definition of the relevant objective function of the government (Alston, Smith, and Vercammen, p. 543, paragraph 2)." The objective function that generates equations (1) and (2) (see the Appendix) is the same as the objective function used by Gardner (1995) when he first questioned Alston, Carter, and Smith's claim that a "domestic distortion can make a border intervention efficient in transferring surplus from consumers and taxpayers to farmers." The objective function used by Gardner (1995) is the same objective function used in the contributions that precede it and thus defines the literature on the debate about borderversus- domestic intervention (Streeten; Yeh; Paarlberg 1984, 1985; Orden; Gardner 1985). The objective function in the latter literature is the same as the one implied in another literature that originates from Wallace and includes most notably Gardner (1983), but also Alston and Hurd. Amer. J. Agr. Econ. 86(2) (May 2004): 549-552 Copyright 2004 American Agricultural Economics Association This content downloaded on Tue, 15 Jan 2013 07:58:41 AM All use subject to JSTOR Terms and Conditions 550 May 2004 Amer. J. Agr. Econ. The objective function in Holloway is this same objective function-it is, of course, Marshallian surplus.1 The third disagreement concerns scholarship. The Comment does not seem to be cognizant of several important papers, especially Bhagwati and Ramaswami, and Bhagwati, both of which precede Corden (1974, 1997); but also Lipsey and Lancaster, and Moschini and Sckokai; one important aspect of Alston and Hurd; and one extremely important result in Holloway. This oversight has some unfortunate repercussions. First, it misdirects to the wrong origins of intellectual property. Second, it misleads about the appropriateness of some welfare calculations. Third, it prevents Alston, Smith, and Vercammen from linking a finding in Holloway (pp. 242-43) with an old theorem (Lipsey and Lancaster) that settles the controversy (Alston, Carter, and Smith 1993, 1995; Gardner 1995; and, presently, Alston, Smith, and Vercammen) about the efficiency of border intervention in the presence of domestic distortions.

An experiment in the Assimilation of Data in Dynamical Analysis

A system for continuous data assimilation is presented and discussed. To simulate the dynamical development a channel version of a balanced barotropic model is used and geopotential (height) data are assimilated into the models computations as data become available. In the first experiment the updating is performed every 24th, 12th and 6th hours with a given network. The stations are distributed at random in 4 groups in order to simulate 4 areas with different density of stations. Optimum interpolation is performed for the difference between the forecast and the valid observations. The RMS-error of the analyses is reduced in time, and the error being smaller the more frequent the updating is performed. The updating every 6th hour yields an error in the analysis less than the RMS-error of the observation. In a second experiment the updating is performed by data from a moving satellite with a side-scan capability of about 15°. If the satellite data are analysed at every time step before they are introduced into the system the error of the analysis is reduced to a value below the RMS-error of the observation already after 24 hours and yields as a whole a better result than updating from a fixed network. If the satellite data are introduced without any modification the error of the analysis is reduced much slower and it takes about 4 days to reach a comparable result to the one where the data have been analysed.