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161.
The emergence of an environmental movement in post-apartheid South Africa has involved the reframing of the environment as a ‘brown’ issue, articulating the discourse of social and environmental justice and a rights-based notion of democracy. Environmental movements have pursued a dual strategy of deliberation and activist opposition. Environmental movements have deployed science to pursue the strategic task of democratic opposition and have established networks of environmental knowledge and expertise. Ecological modernization is the dominant approach to environmental governance and adopts a science-based policy approach. In this context the regulation and management of the environment is premised on the need for science, which provides the authoritative basis for a regulatory response. In local environmental movements, there exists a fundamental tension between a cumulative history of lay knowledge about pollution and the lack of official acknowledgement of qualitative narratives. This is accompanied by a lack and suspicion of reliable official data. Environmental movements have thus employed ‘civic science’ strategically to place the issue of air pollution on the political agenda. This paper uses the case of environmental politics in Durban to reflect on the ways in which civic science and lay knowledge, together constituting community hybrid knowledge, are produced and disseminated in order to pressure the state and capital. The three ways in which knowledge is deployed are: to frame environmental problems, in strategies of oppositional advocacy, and in deliberative policy forums. Empirical analysis shows that civic science is produced through knowledge networks, and both lay knowledge and civic science are opportunistically used by environmental movements to engage both inside and outside formal policy making arenas. This deployment of hybrid knowledge by environmental movements represents a broader challenge to the power of science and technology based on increasing evidence of the hazards and risks facing ordinary people in their daily lives. 相似文献
162.
Yacine Ali-Haïmoud Christopher M. Hirata Clive Dickinson 《Monthly notices of the Royal Astronomical Society》2009,395(2):1055-1078
We present a comprehensive treatment of the spectrum of electric dipole emission from spinning dust grains, updating the commonly used model of Draine & Lazarian. Grain angular velocity distributions are computed using the Fokker–Planck equation; we revisit the drift and diffusion coefficients for the major torques on the grain, including collisions, grain-plasma interactions and infrared emission. We use updated grain optical properties and size distributions. The theoretical formalism is implemented in the companion code, spdust , which is publicly available. The effect of some environmental and grain parameters on the emissivity is shown and analysed. 相似文献
163.
Radiocarbon sequences from some northern Mediterranean cave sites show a temporal gap between Mesolithic and Neolithic occupations. Some authors regard this as a regional phenomenon and have sought to explain it in terms of a general population decline in the late Mesolithic, which facilitated the replacement of indigenous foragers by immigrant farmers. New evidence from the rockshelter site of Mala Triglavca, in Slovenia, leads us to question this view. We describe the deposits in the rockshelter and discuss the results of AMS radiocarbon dating of bone samples recovered in excavations in the 1980s. New archaeological investigations and associated soil/sediment analyses show that in the central part of the rockshelter a well‐defined stratigraphic sequence can be established, despite post‐depositional modification by soil forming processes. There is also evidence of substantial post‐depositional disturbance of the cave sediments by human agency and geomorphological processes, which have created “temporal gaps” and “inversions” in the radiocarbon sequence. The relatively large series of radiocarbon dates obtained enables some of the post‐depositional processes to be identified. © 2008 Wiley Periodicals, Inc. 相似文献
164.
Yaser A. Hafez Rod D. Davies Richard J. Davis Clive Dickinson Elia S. Battistelli Francisco Blanco Kieran Cleary Thomas Franzen Ricardo Genova-Santos Keith Grainge Michael P. Hobson Michael E. Jones Katy Lancaster Anthony N. Lasenby Carmen P. Padilla-Torres José Alberto Rubiño-Martin Rafael Rebolo Richard D. E. Saunders Paul F. Scott Angela C. Taylor David Titterington Marco Tucci Robert A. Watson 《Monthly notices of the Royal Astronomical Society》2008,388(4):1775-1786
Accurate calibration of data is essential for the current generation of cosmic microwave background (CMB) experiments. Using data from the Very Small Array (VSA), we describe procedures which will lead to an accuracy of 1 per cent or better for experiments such as the VSA and CBI. Particular attention is paid to the stability of the receiver systems, the quality of the site and frequent observations of reference sources. At 30 GHz the careful correction for atmospheric emission and absorption is shown to be essential for achieving 1 per cent precision.
The sources for which a 1 per cent relative flux density calibration was achieved included Cas A, Cyg A, Tau A and NGC 7027 and the planets Venus, Jupiter and Saturn. A flux density, or brightness temperature in the case of the planets, was derived at 33 GHz relative to Jupiter which was adopted as the fundamental calibrator. A spectral index at ∼30 GHz is given for each.
Cas A, Tau A, NGC 7027 and Venus were examined for variability. Cas A was found to be decreasing at 0.394 ± 0.019 per cent yr−1 over the period 2001 March to 2004 August. In the same period Tau A was decreasing at 0.22 ± 0.07 per cent yr−1 . A survey of the published data showed that the planetary nebula NGC 7027 decreased at 0.16 ± 0.04 per cent yr−1 over the period 1967–2003. Venus showed an insignificant (1.5 ± 1.3 per cent) variation with Venusian illumination. The integrated polarization of Tau A at 33 GHz was found to be 7.8 ± 0.6 per cent at position angle =148°± 3°. 相似文献
The sources for which a 1 per cent relative flux density calibration was achieved included Cas A, Cyg A, Tau A and NGC 7027 and the planets Venus, Jupiter and Saturn. A flux density, or brightness temperature in the case of the planets, was derived at 33 GHz relative to Jupiter which was adopted as the fundamental calibrator. A spectral index at ∼30 GHz is given for each.
Cas A, Tau A, NGC 7027 and Venus were examined for variability. Cas A was found to be decreasing at 0.394 ± 0.019 per cent yr
165.
Paul?BehrensEmail author J.?O’Sullivan R.?Archer S.?Bradley 《Boundary-Layer Meteorology》2012,143(1):97-106
Recent investigations in complex terrain have found that remote sensing instrumentation commonly finds mean wind-speed differences
when compared to cup anemometery. In many cases the difference is found to be an underestimation and varies from 2 to 9% depending
on topology. We describe these differences in a theoretical sense for a five-beam sodar. An investigation is conducted on
a New Zealand ridge with a five-beam sodar and three computational models, consisting of a potential flow model and two computational
fluid dynamical simulations, OpenFOAM and the industry standard software WindSim. All models predict the difference to within
0.1–2.5%. A comparative assessment is made and it is found that, given the computing overheads, the potential flow model provides
a good compromise in the prediction of mean wind-speed difference. 相似文献
166.
László Kocsis Clive N. Trueman Martin R. Palmer 《Geochimica et cosmochimica acta》2010,74(21):6077-6092
Fossil bones and teeth are potentially important repository for geochemical proxy data and a target for radiometric dating. The concentration of many trace elements in bones and teeth increases by orders of magnitude after death and it is this diagenetic incorporation that forms the basis for several areas of geochemical study. The use of bones and teeth in this context relies on two assumptions: first, that target metal ions are incorporated rapidly after death, reflecting a known environmental signal, and second, that after early incorporation, the bone or tooth remains as an essentially closed system, resistant to later diagenetic change. A wide literature has developed exploring these assumptions, but relatively little direct evidence has been used to assess the long-term diagenetic stability of trace elements within bones and teeth. In this study, we use the Lu-Hf isotope system to show that bones and teeth of Cretaceous and Triassic age from both terrestrial and marine settings experience continued, long-term diagenetic change, most likely through gradual addition of trace elements. Modelling suggests that diagenetic addition after initial recrystallisation may account for >50% of the total REE content in the sampled bones, the extent depending on initial uptake conditions. Tooth enamel and enameloid may be more resistant to late diagenetic changes, but dentine is probably altered to the same extent as bone. These results have significant implications for the use of bones and teeth as hosts of chronological, palaeoceanographic, palaeoenvironmental and taphonomic information, particularly in Mesozoic and Palaeozoic contexts. 相似文献
167.
Geoengineering climate by stratospheric sulfur injections: Earth system vulnerability to technological failure 总被引:1,自引:1,他引:0
Victor Brovkin Vladimir Petoukhov Martin Claussen Eva Bauer David Archer Carlo Jaeger 《Climatic change》2009,92(3-4):243-259
We use a coupled climate–carbon cycle model of intermediate complexity to investigate scenarios of stratospheric sulfur injections as a measure to compensate for CO2-induced global warming. The baseline scenario includes the burning of 5,000 GtC of fossil fuels. A full compensation of CO2-induced warming requires a load of about 13 MtS in the stratosphere at the peak of atmospheric CO2 concentration. Keeping global warming below 2°C reduces this load to 9 MtS. Compensation of CO2 forcing by stratospheric aerosols leads to a global reduction in precipitation, warmer winters in the high northern latitudes and cooler summers over northern hemisphere landmasses. The average surface ocean pH decreases by 0.7, reducing the calcifying ability of marine organisms. Because of the millennial persistence of the fossil fuel CO2 in the atmosphere, high levels of stratospheric aerosol loading would have to continue for thousands of years until CO2 was removed from the atmosphere. A termination of stratospheric aerosol loading results in abrupt global warming of up to 5°C within several decades, a vulnerability of the Earth system to technological failure. 相似文献
168.
Ben?G.?MasonEmail author David?M.?Pyle Clive?Oppenheimer 《Bulletin of Volcanology》2004,66(8):735-748
A compilation and analysis of the size and frequency of the largest known explosive eruptions on Earth are presented. The largest explosive events are defined to be those eruptions yielding greater than 1015 kg of products (>150 times the mass of the 1991 eruption of Mt. Pinatubo). This includes all known eruptions with a volcanic explosivity index (VEI) of 8. A total of 47 such events, ranging in age from Ordovician to Pleistocene, are identified, of which 42 eruptions are known from the past 36 Ma. A logarithmic magnitude scale of eruption size is applied, based on erupted mass, to these events. On this scale, 46 eruptions >1015 kg are defined to be of magnitude M8. There is one M9 event known so far, the Fish Canyon Tuff, with an erupted mass of >1016 kg and a magnitude of 9.2. Analysis of this dataset indicates that eruptions of size M8 and larger have occurred with a minimum frequency of 1.4 events/Ma in two pulses over the past 36 Ma. On the basis of the activity during the past 13.5 Ma, there is at least a 75% probability of a M8 eruption (>1015 kg) occurring within the next 1 Ma. There is a 1% chance of an eruption of this scale in the next 460–7,200 years. While the effect of any individual M8 or larger eruption is considerable, the time-averaged impact (i.e., erupted mass×frequency) of the very largest eruptions is small, due to their rarity. The long-term, time-averaged erupted mass flux from magnitude 8 and 9 eruptions is ~10–100 times less than for M7 eruptions; the time-averaged mass eruption rate from M7 eruptions is 9,500 kg s–1, whereas for M8 and M9 eruptions it is ~70–1,000 kg s–1. Comparison of the energy release by volcanic eruptions with that due to asteroid impacts suggests that on timescales of <100,000 years, explosive volcanic eruptions are considerably more frequent than impacts of similar energy yield. This has important implications for understanding the risk of extreme events.Editorial responsibility: R. Cioni 相似文献
169.
Norman?KerleEmail author Benjamin?van?Wyk de Vries Clive?Oppenheimer 《Bulletin of Volcanology》2003,65(5):331-345
During unusually high rainfall associated with Hurricane Mitch in 1998, a flank collapse leading to a disastrous lahar occurred at Casita volcano, Nicaragua. The lack of a similar failure during a rainfall event of comparable magnitude in 1982 (Tropical Storm Alleta) suggests that additional factors influenced the 1998 collapse. We have investigated the potential contribution of erosional flank undercutting, seismic activity and anthropogenic land-cover change at the collapse site. Except for seismic events prior to Mitch, which may have increased flank instability, none of these factors appears significant. Instead, for failure to occur, the following conditions were required: (1) highly fractured slope material allowing deep and rapid infiltration of meteoric water, (2) a less permeable underlying layer to obstruct drainage, (3) strong, continuous antecedent rainfall to build up high pore-water pressure, and (4) episodic, high-intensity precipitation during Mitch to generate recurrent pressure waves. Prerequisite (1) was provided by edifice-wide deformation towards the south-east, seismic activity and proximity to a prominent fault, and local subsidence. Condition (2) was met by clay-rich layers resulting from hydrothermal alteration. More than 1,900 mm of rain fell in the 6 months prior to Mitch without significant interruption, while intense episodic precipitation occurred during the hurricane, satisfying conditions (3) and (4), respectively. The main difference with Alleta was that it occurred at the beginning of the rainy season and, therefore, without sufficient antecedent rainfall. Anthropogenic activity, including land-cover change, did not affect slope stability (i.e. the hazard). However, vulnerability was generated when two towns were established in the lowlands south of Casita, on top of previous lahar deposits. It was greatly increased when approximately 4 km of forest between the collapse site and the towns were cleared, paving the way for a largely unobstructed debris flow. Deforestation also facilitated erosion along the flanks to provide about 78% of the material contained in the lahar when it destroyed the towns, killing more than 2,500 people. 相似文献
170.
Clive Wilkinson 《Climatic change》2005,73(1-2):155-167
The large-scale study of ship's logbooks for climatic data has revealed the wide and varied potential of this under-exploited
resource for the study of the past. As well as being of utility to climatologists, the daily recording of shipboard information
can help illuminate a number of themes of interest to maritime and naval historians. More than this, however, such studies
can help inform both more general and other specialized historical studies. Logbooks contain both anecdotal and statistical
data relevant to the studies of medical historians, the history of science and navigation, social history, economic history,
warfare, imperial history and of course environmental history. Moreover, many of these themes can be studied in a multi-national
context and furthermore, if studied in a multi-disciplinary context, can offer many useful insights. 相似文献