A deep burrowing sipunculan of ecological and geochemical importance     

Mark A. Shields  Monika Kedra 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2057-2064

In late 1980s, a dense network of deep capillary burrows was reported on the Vøring Plateau, Nordic Seas, and associated with a sipunculan belonging to the genus Nephasoma. This sipunculan was responsible for rapid transport of organic matter from the sediment surface down a deep burrow network. Over 460 specimens belonging to the genus Nephasoma were collected from the deep Nordic Seas during four cruises from 2000–2005 and four species identified: Nephasoma abyssorum abyssorum, N. diaphanes diaphanes, N. diaphanes corrugatum and N. lilljeborgi. The species responsible for the deep burrows and rapid subduction of organic matter can now be confirmed as Nephasoma lilljeborgi. Deep burrows associated with N. lilljeborgi were observed on the Vøring Plateau, Bear Island Fan, Svalbard Margin and Yermak Plateau and may be a seabed feature endemic to the Nordic Seas region. N. lilljeborgi could have a significant role in influencing the ecology and geochemistry of the Nordic Seas region. It is recommended that future benthic community studies in the Nordic Seas region confirm the species identity of sipunculan specimens in order to determine the ecological and geochemical importance of the specimens.  相似文献   

基于空间计量模型的中国城市化发展与城市空气质量关系   总被引：1，自引：0，他引：1  

姜磊  周海峰  柏玲 《热带地理》2019,39(3):461-471

采用中国289个地级及以上城市2016年的空气质量指数（AQI）和夜间灯光数据，运用空间滞后模型，从空间溢出效应视角出发探究了城市化发展与空气质量之间的定量关系。从空间滞后模型的估计结果来看，城市空气污染存在显著的空间溢出效应，周边地区空气质量的下降会导致本地空气污染情况加重。在城市发展过程中，城市经济发展水平的提高，引致的城市建设用地的扩张使得空气质量不断恶化；政府管制力的加强对空气污染的治理起到了促进作用，而居民环保意识和城市技术创新水平的提高有利于空气质量的改善。此外，PM2.5质量浓度的上升导致空气质量恶化。公路货运量在统计上与空气质量的关系不显著。从研究结果来看，协调城市发展与空气质量的关系以及加强空气污染防治的联防联控机制，是未来空气污染治理工作的重点。  相似文献   

京津冀地区农业生产效率的时空格局及收敛性研究     

方方 《世界地理研究》2019,28(5):130-140

将京津冀地区146个典型县域划分为京津近郊农业区（I）、冀东北农业区（II）、冀中平原农业区（III）、太行山农业区（IV）、坝上农业区（V）五大农业区，测算了2000—2015年京津冀及五大农业区的农业生产效率，检验了京津冀及五大农业区农业生产效率的收敛性，揭示了京津冀地区农业生产效率的收敛机理。研究结果表明，京津冀地区农业生产效率变化趋势总体较为平稳，五大农业区农业生产效率由大到小依次为：V>II>IV>I>III，Malmquist指数呈显著波动趋势，技术进步对对农业生产效率提升的作用显著；在农业资源禀赋、地理区位等内源性因素与经济发展环境、技术进步与农业政策支持等外源性因素的共同作用下，京津冀地区优化重组农业生产要素，提升了农业生产效率，并通过要素流动与要素替代作用，缩小了不同农业区内部的农业生产效率差距，使不同经济发展水平的各农业区农业生产效率收敛于不同稳态水平；最后，从现代农业生产经营体系、财政转移支付机制、农业规模经营等角度提出了京津冀地区农业协同发展的具体路径。  相似文献   

The special climate change fund: origins and prioritisation assessment     

Valentina Bosetti  Marzio Galeotti  Alessandro Lanza 《Climate Policy》2013,13(3):295-312

Abstract

A central issue in tackling climate change is to understand to what extent different short-term mitigation strategies are consistent with long-term stabilization targets. The present article aims at cross-comparing emission paths derived by plausible short-term policies against those implied by long-term climate targets, comparing, for example, differences in peak periods. Short-term policies considered are, for instance, Kyoto-type targets with or without participation by the USA and/or by developing countries. Long-term targets focus instead on stabilization of CO₂ concentrations, radiative forcing and the increase in atmospheric temperature relative to pre-industrial levels. In order to account for the uncertainty surrounding the climate cycle, for each long-term goal multiple paths of emission—the most probable, the optimistic and the pessimistic projections—are considered in the comparison exercise. Comparative analysis is performed using the FEEM-RICE model, a regional economy—climate model. The results suggest that some early policy action should take place for short-term emissions to be compatible with long-term targets. In particular, the Kyoto-type regimes appear to be on a compatible emission path, at least up to the second commitment period. However, this is no longer the case when assuming a pessimistic realization of the uncertain climate parameters.  相似文献   

一种基于最佳指数模型的 TM 遥感影像最佳波段组合计算方法     

许泉立  ;易俊华 《东北测绘》2014,(4):32-35

如何通过定量计算选择最佳波段组合一直是TM等多波段遥感影像信息提取的研究热点。本文综合利用Erdas提供的可视化空间建模工具（ Spatial Modeler ）和面向对象的编程技术,提出了一种基于最佳指数（ Opti-mum Index Factor ,OIF）的定量计算与定性分析相结合的TM遥感影像最佳波段组合方法。实验证明,该方法快速有效,极大提升了TM等多波段遥感影像最佳波段组合的计算过程。  相似文献   

2003年淮河流域致洪暴雨过程的环流背景及其前兆信号   总被引：7，自引：2，他引：5  

程华琼  陈菊英 《地球物理学进展》2004,19(2):465-473

分析研究了2003年夏季淮河流域致洪暴雨过程的时空分布特征及其前期和同期欧亚地区环流背景的逐日变化特征,重点分析了致洪暴雨过程发生前后乌山地区阻塞高压强度指数(UBHII)逐日变化特征及其对淮河流域致洪暴雨过程的影响．结果表明：2003年淮河流域持续性强暴雨过程均发生在鸟山阻塞高压强高峰后的减弱期,即在淮河流域发生持续性强暴雨过程之前乌山阻塞高压就发生了突变;同时发现西太平洋副热带高压加强并登陆后的,其北界的位置变化对淮河流域致洪暴雨过程的发生和持续也有十分重要的作用．因此,乌拉尔山阻塞高压异常加强后的突然减弱和西太平洋副热带高压的加强并西进登陆,是淮河流域地区发生持续性暴雨过程的两个重要前兆．  相似文献   

The economic impact of extreme sea-level rise: Ice sheet vulnerability and the social cost of carbon dioxide     

《Global Environmental Change》2014

The possibility of extreme sea-level rise is one of the commonly cited reasons for concern about climate change. Major increases in sea level would likely be driven by the melting or collapse of major ice sheets. This possibility has implications for the social cost of carbon dioxide, which is a key policy value as well as a useful summary measure of damage caused by greenhouse gas emissions.This paper extends earlier work on the importance of low-probability, high-impact events for the social cost of carbon dioxide to incorporate the possibility of extreme sea-level rise.To estimate its impact, an integrated assessment model is used, which allows a probabilistic assessment of climate change damages based on the linkages between the economic and climate systems. In the model, the generic discontinuity damage is replaced with the possibility of large-scale damage from factors that are taken to be correlated with temperature rise and, crucially for this paper, explicit consideration of extreme sea-level rise.Estimates of the amount of increase in the social cost of carbon dioxide that can be expected from incorporating extreme sea-level rise show that the increase is significant, though not especially large in percentage terms.The paper contributes to the literature of how to represent uncertain climate impacts in integrated assessment models and the associated estimation of the social cost of carbon dioxide.  相似文献   

Risk mitigation and the social cost of carbon     

《Global Environmental Change》2014

The social cost of carbon – i.e., the marginal present-value cost imposed by greenhouse gas emissions – is determined by a complex interaction between factual assumptions, modeling methods, and value judgments. Among the most crucial factors is society's willingness to tolerate potentially catastrophic environmental risks. To explore this issue, the present analysis employs a stochastic climate–economy model that accounts for uncertainties in baseline economic growth, baseline emissions, greenhouse gas mitigation costs, carbon cycling, climate sensitivity, and climate change damages. In this model, preferences are specified to reflect the high degree of risk aversion revealed by private investment decisions, signaled by the large observed gap between the average rates of return paid by safe and risky financial instruments. In contrast, most climate–economy models assume much lower risk aversion. Given high risk aversion, the analysis finds that investment in climate stabilization yields especially large net benefits by forestalling low-probability threats to long-run human well-being. Accordingly, the social cost of carbon attains the markedly high value of $25,700 per metric ton of carbon dioxide in a baseline scenario in which emissions are unregulated. This value falls to just $4 per ton as the stringency of control measures is successively increased. These results cast doubt on the idea that the social cost of carbon takes on a uniquely defined, objective value that is independent of policy decisions. This does not, however, rule out the use of carbon prices to achieve the benefits of climate stabilization using least-cost mitigation measures.  相似文献   

Politics eclipses climate extremes for climate change perceptions     

《Global Environmental Change》2014

Whether or not actual shifts in climate influence public perceptions of climate change remains an open question, one with important implications for societal response to climate change. We use the most comprehensive public opinion survey data on climate change available for the US to examine effects of annual and seasonal climate variation. Our results show that political orientation has the most important effect in shaping public perceptions about the timing and seriousness of climate change. Objective climatic conditions do not influence Americans’ perceptions of the timing of climate change and only have a negligible effect on perceptions about the seriousness of climate change. These results suggest that further changes in climatic conditions are unlikely to produce noticeable shifts in Americans’ climate change perceptions.  相似文献   

Elevation,slope aspect and integrated nutrient management effects on crop productivity and soil quality in North-west Himalayas,India     

Birendra Nath Ghosh  Narinder Kumar Sharma  Nurnabi Meherul Alam  Raman Jeet Singh  Gopal Prasad Juyal 《山地科学学报》2014,11(5):1208-1217

On farm bio-resource recycling has been given greater emphasis with the introduction of conservation agriculture specifically withclimate change scenarios in the mid-hills of the north-west Himalaya region（NWHR）. Under this changing scenario, elevation, slope aspect and integrated nutrient management（INM） may affect significantly soil quality and crop productivity. A study was conducted during 2009-2010 to 2010-2011 at the Ashti watershed of NWHR in a rainfed condition to examine the influence of elevation, slope aspect and integrated nutrient management（INM） on soil resource and crop productivity. Two years of farm demonstration trials indicated that crop productivity and soil quality is significantly affected by elevation, slope aspect and INM. Results showed that wheat equivalent yield（WEY） of improved technology increased crop productivity by -20%-37% compared to the conventional system. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-17%. North aspect and higher elevation increased crop productivity by 15%-25% compared to south aspect and low elevation（except paddy）. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-15%. Irrespective of slope, elevation and cropping system, the WEY increased by -30% in this region due to INMtechnology. The influence of elevation, slope aspect and INM significantly affected soil resources（SQI） and soil carbon change（SCC）. SCC is significantly correlated with SQI for conventional（R2 = 0.65＊）, INM technology（R2 = 0.81＊） and for both technologies（R2 = 0.73＊）. It is recommended that at higher elevation.（except for paddy soils） with a north facing slope, INM is recommended for higher crop productivity; conservation of soil resources is recommended for the mid hills of NWHR; and single values of SCC are appropriate as a SQI for this region.  相似文献