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171.
While the Conference of the Parties wrangle at an international scale with climate policy, a quiet set of policies and measures is being implemented at a local scale by municipalities across the globe. This study examines the motivation municipalities have for undertaking policies to reduce their greenhouse gas emissions, when the theory of free-ridingwould predict that local administrations should find it difficult to unilaterally reduce their emissions for the benefit of the global climate. Through interviews with officials and/or staff in 23 municipalities in the United States enacting climate policy, data are gathered that suggest local government abatement policies are primarily a top—down decision based on what officials or staff members believe to be “good business” or rational policy choices. They are primarily driven by the potential for realised or perceived cost savings and co-benefits rather than by public pressure. Economic data from some dozen municipal projects are analyzed, finding, while municipalities lack sophisticated accounting techniques, some justification for the often-disputed claim that at least initial reductions in emissions can be made at cost savings. In the United States, with the lack of national abatement policies, it is municipalities that are leading the way in beginning to implement mitigation strategies, even if only for initial reductions.  相似文献   
172.
We have collected and analyzed a larger set of stream waters for major ions and strontium isotopes in Taylor Valley, McMurdo Dry Valleys, Antarctica. These new data substantiate the concept that the dissolution of carbonate minerals is a significant source of strontium, even in polar desert environments where liquid water is primarily limited to stream channels. In Taylor Valley, most of the carbonate minerals present are the result of secondary processes, such as mineral precipitation and/or eolian deposition, and not through primary geologic sources, such as bedrock or till sources. In Von Guerard Stream (Lake Fryxell basin) and Andersen Creek (Lake Hoare basin), water samples were collected during the austral summer to determine short-term 87Sr/86Sr patterns. The observed variability in both time and space may be dependent on the relative amounts of primary and secondary carbonates present in the streambeds and hyporheic zone as well as contingent on the relative proportions of carbonate and aluminosilicate weathering.  相似文献   
173.
Peak-ring basins represent an impact-crater morphology that is transitional between complex craters with central peaks and large multi-ring basins. Therefore, they can provide insight into the scale dependence of the impact process. Here the transition with increasing crater diameter from complex craters to peak-ring basins on Mercury is assessed through a detailed analysis of Eminescu, a geologically recent and well-preserved peak-ring basin. Eminescu has a diameter (∼125 km) close to the minimum for such crater forms and is thus representative of the transition. Impact crater size-frequency distributions and faint rays indicate that Eminescu is Kuiperian in age, geologically younger than most other basins on Mercury. Geologic mapping of basin interior units indicates a distinction between smooth plains and peak-ring units. Our mapping and crater retention ages favor plains formation by impact melt rather than post-impact volcanism, but a volcanic origin for the plains cannot be excluded if the time interval between basin formation and volcanic emplacement was less than the uncertainty in relative ages. The high-albedo peak ring of Eminescu is composed of bright crater-floor deposits (BCFDs, a distinct crustal unit seen elsewhere on Mercury) exposed by the impact. We use our observations to assess predictions of peak-ring formation models. We interpret the characteristics of Eminescu as consistent with basin formation models in which a melt cavity forms during the impact formation of craters at the transition to peak ring morphologies. We suggest that the smooth plains were emplaced via impact melt expulsion from the central melt cavity during uplift of a peak ring composed of BCFD-type material. In this scenario the ringed cluster of peaks resulted from the early development of the melt cavity, which modified the central uplift zone.  相似文献   
174.
Abstract– The composition of the most primitive solar system condensates, such as calcium‐aluminum‐rich inclusions (CAIs) and micron‐sized corundum grains, show that short‐lived radionuclides (SLR), e.g., 26Al, were present in the early solar system. Their abundances require a local or stellar origin, which, however, is far from being understood. We present for the first time the abundances of several SLR up to 60Fe predicted from stars with initial mass in the range approximately 7–11 M. These stars evolve through core H, He, and C burning. After core C burning they go through a “Super”‐asymptotic giant branch (Super‐AGB) phase, with the H and He shells activated alternately, episodic thermal pulses in the He shell, a very hot temperature at the base of the convective envelope (approximately 108 K), and strong stellar winds driving the H‐rich envelope into the surrounding interstellar medium. The final remnants of the evolution of Super‐AGB stars are mostly O–Ne white dwarfs. Our Super‐AGB models produce 26Al/27Al yield ratios approximately 0.02–0.26. These models can account for the canonical value of the 26Al/27Al ratio using dilutions with the solar nebula of the order of 1 part of Super‐AGB mass per several 102 to several 103 of solar nebula mass, resulting in associated changes in the O‐isotope composition in the range Δ17O from 3 to 20‰. This is in agreement with observations of the O isotopic ratios in primitive solar system condensates, which do not carry the signature of a stellar polluter. The radionuclides 41Ca and 60Fe are produced by neutron captures in Super‐AGB stars and their meteoritic abundances are also matched by some of our models, depending on the nuclear and stellar physics uncertainties as well as the meteoritic experimental data. We also expect and are currently investigating Super‐AGB production of SLR heavier than iron, such as 107Pd.  相似文献   
175.
A new prediction technique based on logarithmic values is proposed to predict the maximum amplitude (R m) of a solar cycle from the preceding minimum aa geomagnetic index (aa min). The correlation between lnR m and lnaa min (r=0.92) is slightly stronger than that between R m and aa min (r=0.90). From this method, cycle 24 is predicted to have a peak size of R m(24)=81.7(1±13.2%). If the suggested error in aa (3 nT) before 1957 is corrected, the correlation coefficient between R m and aa min (r=0.94) will be slightly higher, and the peak of cycle 24 is predicted much lower, R m(24)=52.5±13.1. Therefore, the prediction of R m based on the relationship between R m and aa min depends greatly on the accurate measurement of aa.  相似文献   
176.
Rae Glacier is a small cirque glacier located in the front ranges of the Canadian Rocky Mountains. In 1990 and 1991 field research was completed to describe the physical glaciology of Rae Glacier and to characterize historical glaciological trends at the site. Ablation and surface movement rates were measured using a network of stakes drilled into the glacier and radio-echo sounding was used to describe local ice depths.

Rae Glacier has experienced a significant loss in size and mass during the historical period, owing to a lengthy interval of negative mass-balance conditions. The glacier has decreased in surface area by over 50% and now contains less than 24% of the ice it did at the end of the last century.

Surface-ice velocity varied between 1.4 and 5.4 m from 1990 to 1991. Rates of ice ablation proved to be highly variable, with steeper areas showing up to 50% more ablation. Combined with data on the emergent flow component of the glacier, the ablation data suggest that the glacier presently is unable to replenish the amount of ice annually being lost to ablation. The glacier has a lag time of 5 to 10 years, which confirms that it is sensitive to climatic fluctuations and responds to changes in mass balance within a very short time. This observation is supported by an estimated response time of 42 years. [Key words: glaciology, Rae Glacier, Canadian Rocky Mountains.]  相似文献   
177.
Research on New Zealand lakes over the past 25 years has focused mainly on eutrophication, measures of water quality, patterns, processes and production in plankton communities, and the spread and growth of submerged adventive macrophytes. Compared with most northern temperate lakes many New Zealand lakes show: low levels of inorganic nitrogen (N) and frequent N‐limitation of phyto‐plankton growth; diffuse, rather than point source, nutrient inflows; a great diversity of optical properties; unusual and often variable timing of plankton growth (attributed to the pervasive influence of New Zealand's oceanic climate); low productivity and biomass of zooplankton, which appear to be limited by food rather than predators; and sensitivity to invasion by adventive macrophytes. Notable research develop‐ments include improved methods of measuring nutrients, empirical predictive models that relate indices of eutrophication to nutrient loading, and significant advancements in methods of quantifying and measuring water colour and clarity.  相似文献   
178.
Lakes Waihola and Waipori are shallow, coastal, tidal lakes that experience wind‐induced sediment resuspension, saline intrusions, and high inputs of nutrients. To determine the influence of externally‐driven, physical factors on spatial and temporal patterns of water quality in the two lakes, meteorological, hydrological, and water quality data were collected over 1 year. Multivariate analyses indicated that wind energy was driving the main water quality gradient in the lakes, which was primarily related to wind‐induced resuspension of lake sediments. The major, seasonally regulated, non‐tidal freshwater inflow was important in determining nutrient and salinity gradients in the lakes. The main nutrient inputs to the system were identified as the regulated, non‐tidal inflow (the upper Waipori River) and the tidal inflow (lower Waipori River). The impact of water quality gradients on zooplankton community structure in the lakes was assessed by canonical multivariate methods. Salinity gradients, caused by seasonal saltwater intrusions, were strongly related to zooplankton community structure in the lakes. Nutrient gradients (indicative of trophic state) were also related to zooplankton community structure. Although wind‐induced sediment resuspension had the largest impact on water quality in the lakes, it had little impact on the zooplankton community structure in either lake. The relationships between water quality and zooplankton community structure were confounded in Lake Waipori because of its very short hydraulic residence time (annual mean =1.9 days). Zooplankton community structure was resilient to short‐term changes in suspended particulate matter concentrations but not to seasonal changes in salinity. The results of this study support others which have shown impacts of even relatively small variations in salinity on the structure of zooplankton communities. This highlights the vulnerability of zooplankton communities in coastal lakes and wetlands to increasing salinity resulting from sea level rise and global climate change.  相似文献   
179.
180.
There is a growing scholarship on the role of the amateur, and amateur societies, in the production and circulation of weather and climate knowledge in the past. Yet relatively little attention has been paid to the actual and potential contribution of contemporary amateur meteorologists in this respect. In this paper we first examine the importance of the amateur historically in the production of local weather knowledge and also in the emergence of professional meteorology. Drawing on semi-structured interviews with members of one contemporary UK based amateur meteorological organisation??the Climatological Observers Link (COL)??we then investigate the nature and extent of contemporary amateur meteorologists?? contributions to a wide range of different ??publics?? today, which include both popular and professional communities. Finally, we interrogate our interview data to identify whether COL members themselves recognise a wider role for their expertise at a time of increasing popular and scientific interest in weather and climate and in an era when the inclusion of non-certified experts in policy decision making processes is being advocated.  相似文献   
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