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131.
For the last two decades, European climate policy has focused almost exclusively on mitigation of climate change. It was only well after the turn of the century, with impacts of climate change increasingly being observed, that adaptation was added to the policy agenda and EU Member States started to develop National Adaptation Strategies (NASs). This paper reviews seven National Adaptation Strategies that were either formally adopted or under development by Member States at the end of 2008. The strategies are analysed under the following six themes. Firstly, the factors motivating and facilitating the development of a national adaptation strategy. Secondly, the scientific and technical support needed for the development and implementation of such a strategy. Thirdly, the role of the strategy in information, communication and awareness-raising of the adaptation issue. Fourthly, new or existing forms of multi-level governance to implement the proposed actions. Fifthly, how the strategy addresses integration and coordination with other policy domains. Finally, how the strategy suggests the implementation and how the strategy is evaluated. The paper notes that the role of National Adaptation Strategies in the wider governance of adaptation differs between countries but clearly benchmarks a new political commitment to adaptation at national policy levels. However, we also find that in most cases approaches for implementing and evaluating the strategies are yet to be defined. The paper concludes that even though the strategies show great resemblance in terms of topics, methods and approaches, there are many institutional challenges, including multi-level governance and policy integration issues, which can act as considerable barriers in future policy implementation.  相似文献   
132.
The goal of this study was to improve understanding of the factors that influence runoff generation during non‐frozen ground periods in small agricultural watersheds in southwestern Wisconsin where the landscapes are controlled by dolostone bedrock in order to provide agricultural producers with a manure management tool. Six small watersheds (ranging from 6 to 17 ha) within two southwestern Wisconsin farm sites (Discovery Farms Program (DFP) and Pioneer Farm (PF)) were instrumented, and surface runoff was continuously monitored from 2004 to 2007. The soils in all watersheds were formed in deep (~1 m) loessial sites. A direct‐plant management strategy and corn‐soybean crop rotation were utilized within watersheds at DFP. A conventional tillage system (chisel plow in the fall followed by soil finisher in the spring) and a corn‐oat‐alfalfa crop rotation were utilized within watersheds at PF. At PF, the amount of precipitation leaving the landscape as surface runoff (1.8%) was two times greater compared to DFP (0.9%), indicating that the direct‐plant management system was better at retaining precipitation than the chisel plow/soil finisher system. Using breakpoint regression analysis, a non‐linear response in runoff generation with antecedent soil moisture (ASM) was observed with a threshold ASM of 0.39 cm3cm?3 (approximately 80% of total porosity) for all six watersheds. Below this threshold, runoff coefficients were near zero. Above this threshold, runoff coefficients increased with ASM. A non‐linear response in runoff generation with maximum 30 min rainfall intensity (I30) was also observed, and threshold I30 values increased as ASM decreased and as crop cover increased. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
133.
This paper presents a simple algebraic approach to the interpretation of wind erosion data that allows for density variation close to the surface due to the presence of large amounts of saltating material. The effect explains nonlinearities in the logarithmic velocity profile near the surface and extends the profile into the saltating layer.  相似文献   
134.
We investigate how well the variability of extreme daily precipitation events across the United Kingdom is represented in a set of regional climate models and the E-OBS gridded data set. Instead of simply evaluating the climatologies of extreme precipitation measures, we develop an approach to validate the representation of physical mechanisms controlling extreme precipitation variability. In part I of this study we applied a statistical model to investigate the influence of the synoptic scale atmospheric circulation on extreme precipitation using observational rain gauge data. More specifically, airflow strength, direction and vorticity are used as predictors for the parameters of the generalised extreme value (GEV) distribution of local precipitation extremes. Here we employ this statistical model for our validation study. In a first step, the statistical model is calibrated against a gridded precipitation data set provided by the UK Met Office. In a second step, the same statistical model is calibrated against 14 ERA40 driven 25?km resolution RCMs from the ENSEMBLES project and the E-OBS gridded data set. Validation indices describing relevant physical mechanisms are derived from the statistical models for observations and RCMs and are compared using pattern standard deviation, pattern correlation and centered pattern root mean squared error as validation measures. The results for the different RCMs and E-OBS are visualised using Taylor diagrams. We show that the RCMs adequately simulate moderately extreme precipitation and the influence of airflow strength and vorticity on precipitation extremes, but show deficits in representing the influence of airflow direction. Also very rare extremes are misrepresented, but this result is afflicted with a high uncertainty. E-OBS shows considerable biases, in particular in regions of sparse data. The proposed approach might be used to validate other physical relationships in regional as well as global climate models.  相似文献   
135.
We critically review the Kyoto Protocol and thirteen alternative policy architectures for addressing the threat of global climate change. We employ six criteria to evaluate the policy proposals: environmental outcome, dynamic efficiency, cost-effectiveness, equity, flexibility in the presence of new information, and incentives for participation and compliance. The Kyoto Protocol does not fare well on a number of criteria, but none of the alternative proposals fare well along all six dimensions. We identify several major themes among the alternative proposals: Kyoto is “too little, too fast”; developing countries (DCs) should play a more substantial role and receive incentives to participate; implementation should focus on market-based approaches, especially those with price mechanisms; and participation and compliance incentives are inadequately addressed by most proposals. Our investigation reveals tensions among several of the evaluative criteria, such as between environmental outcome and efficiency, and between cost-effectiveness and incentives for participation and compliance.  相似文献   
136.
Measurements of annual travel distance (Lb) of bed load sediment at 16 locations in Alaska, the intermountain USA, west coast USA and Scotland are strongly correlated with bankfull channel width (r2 = 0·86, p < 0·001). Travel distance of particles is probably limited by trapping in bars, which have a longitudinal spacing proportional to channel width. Increased abundance of woody debris reduces bar spacing and may reduce Lb. Longer cumulative duration of bed load transporting flows in a year appears to increase Lb. Other predictors of annual travel distance such as stream power per unit length, drainage area and bankfull discharge were less well correlated with Lb (r2 ranging from 0·27 to 0·51). Stream power per unit bed area, basal shear stress and slope were not significantly related to Lb (r2 < 0·05). Most correlations were improved when regressions were limited to data from the west coast USA. Travel distance estimates can be used to help identify reaches that may take longer to recover from large, short‐term increases in sediment supply. Published in 2001 by John Wiley & Sons, Ltd.  相似文献   
137.
138.
Submarine lava flow morphology is commonly used to estimate relative flow velocity, but the effects of crystallinity and viscosity are rarely considered. We use digital petrography and quantitative textural analysis techniques to determine the crystallinity of submarine basaltic lava flows, using a set of samples from previously mapped lava flow fields at the hotspot-affected Galápagos Spreading Center. Crystallinity measurements were incorporated into predictive models of suspension rheology to characterize lava flow consistency and rheology. Petrologic data were integrated to estimate bulk lava viscosity. We compared the crystallinity and viscosity of each sample with its flow morphology to determine their respective roles in submarine lava emplacement dynamics. We find no correlation between crystallinity, bulk viscosity, and lava morphology, implying that flow advance rate is the primary control on submarine lava morphology. However, we show systematic variations in crystal size and shape distribution among pillows, lobates, and sheets, suggesting that these parameters are important indicators of eruption processes. Finally, we compared the characteristics of lavas from two different sampling sites with contrasting long-term magma supply rates. Differences between lavas from each study site illustrate the significant effect of magma supply on the physical properties of the oceanic upper crust.  相似文献   
139.
140.
Will climate change exacerbate water stress in Central Asia?   总被引:3,自引:0,他引:3  
Millions of people in the geopolitically important region of Central Asia depend on water from snow- and glacier-melt driven international rivers, most of all the Syr Darya and Amu Darya. The riparian countries of these rivers have experienced recurring water allocation conflicts ever since the Soviet Union collapsed. Will climate change exacerbate water stress and thus conflicts? We have developed a coupled climate, land-ice and rainfall-runoff model for the Syr Darya to quantify impacts and show that climatic changes are likely to have consequences on runoff seasonality due to earlier snow-melt. This will increase water stress in unregulated catchments because less water will be available for irrigation in the summer months. Threats from geohazards, above all glacier lake outbursts, are likely to increase as well. The area at highest risk is the densely populated, agriculturally productive, and politically unstable Fergana Valley. Targeted infrastructural developments will be required in the region. If the current mismanagement of water and energy resources can be replaced with more effective resource allocation mechanisms through the strengthening of transboundary institutions, Central Asia will be able to successfully address these future climate-related challenges.  相似文献   
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