山西地震带北段与张家口——渤海地震带不同深度CO_2和Rn气体通量的差异性

2014年在山西地震带北段和张家口—渤海地震带布设35个测量剖面,测量土壤气CO_2、Rn浓度及深度20 cm、1 m的CO_2和Rn通量。测量结果表明:(1) CO_2、Rn浓度与深度20 cm、1 m的CO_2、Rn通量的平均值和最大值变化趋势大致相同,均呈自西向东的增大趋势;(2)深度20 cm、1 m的CO_2和Rn通量相关性均不明显,但1 m深的CO_2、Rn通量明显较高;(3) CO_2和Rn浓度、通量变化主要与区域复杂的地震活动性和断层活动性有关,主要受到地表化学成分和区域岩石地球化学影响。     

温室性气体地质处置研究进展及其问题

温室性气体地质处置的机理有3个:①将深部含水地层作为容器封闭CO2;②含水(油)介质,即岩石矿物与CO2发生化学反应而消耗掉CO2,使CO2长期安全保存于地下介质中;③在低渗透含水层中,CO2的运移与滞留时间较长,属于水力学控制CO2的机制.尽管CO2的地质处置存在费用和安全稳定性问题,但国际上已开展的研究表明,地质处置温室性气体是人类积极解决全球环境问题极具前景的方法之一.     

碳足迹研究现状与演变：基于社会网络视角分析

温室气体减排已成为世界各国的共识,碳足迹分析作为温室气体管理的工具,在过去二十多年来发展迅速,然而国内外现有研究缺乏对其演化发展的归纳总结。因此,本文选取Web of science收录的期刊数据为研究对象,检索出1996—2017年有关碳足迹的相关文献8840篇,并对此进行了定性和定量分析。结果表明：①美国对碳足迹文献的贡献最大,拥有2275篇出版物以及最高的h指数（83）和被引频次（34803）;②中国和印度等发展中国家近10年发文量增长显著,都位于全球发文量前十的国家中;③荷兰的h指数占总出版物的比重最大;④加利福尼亚大学是该领域最具生产力的机构,拥有222篇出版物,且国际合作水平显著。最后,论文将碳足迹研究分为三个阶段,基于关键词共现分析,厘清碳足迹研究的热点变化,并预测其未来研究趋势。     

市域尺度货物运输碳排放时空变化及因素分析

针对货物运输导致碳排放成为温室气体主要来源之一的问题,该文综合货物运输车辆的微观温室气体排放及时空变化,从市域尺度分析货物运输碳排放的时空变化规律。利用微观排放模型计算了2000年、2005年、2010年和2015年全国286个城市货物运输碳排放的空间分布及其变化,并应用地理加权回归模型探究城市化不同层面因素对碳排放时空分布变化的影响。结果表明:货物运输碳排放具有显著的空间集聚特征,且高排放地区的集聚规律更加显著;地理加权回归模型精度明显高于普通线性回归模型,经济变量、人口变量、货运强度变量与货物运输碳排放存在显著正相关关系。该研究可为中国各市级区域制订节能减排政策提供量化的科学依据。     

Quality assessment of digital surface models extracted from WorldView-2 and WorldView-3 stereo pairs over different land covers

Digital surface models (DSMs) extracted from very high resolution (VHR) satellite stereo images are becoming more and more important in a wide range of geoscience applications. The number of software packages available for generating DSMs has been increasing rapidly. The main goal of this work is to explore the capabilities of VHR satellite stereo pairs for DSMs generation over different land-cover objects such as agricultural plastic greenhouses, bare soil and urban areas by using two software packages: (i) OrthoEngine (PCI), based on a hierarchical subpixel mean normalized cross correlation matching method, and (ii) RPC Stereo Processor (RSP), with a modified hierarchical semi-global matching method. Two VHR satellite stereo pairs from WorldView-2 (WV2) and WorldView-3 (WV3) were used to extract the DSMs. A quality assessment on these DSMs on both vertical accuracy and completeness was carried out by considering the following factors: (i) type of sensor (i.e., WV2 or WV3), (ii) software package (i.e., PCI or RSP) and (iii) type of land-cover objects (plastic greenhouses, bare soil and urban areas). A highly accurate light detection and ranging (LiDAR) derived DSM was used as the ground truth for validation. By comparing both software packages, we concluded that regarding DSM completeness, RSP produced significantly (p < 0.05) better scores than PCI for all the sensors and type of land-cover objects. The percentage improvement in completeness by using RSP instead of PCI was approximately 2%, 18% and 26% for bare soil, greenhouses and urban areas respectively. Concerning the vertical accuracy in root mean square error (RMSE), the only factor clearly significant (p < 0.05) was the land cover. Overall, WV3 DSM showed slightly better (not significant) vertical accuracy values than WV2. Finally, both software packages achieved similar vertical accuracy for the different land-cover objects and tested sensors.     

基于CFD的自然通风对日光温室湿度分布模拟分析

以济南日光温室为研究对象,基于试验观测数据,采用计算流体力学（computational fluid dynamics, CFD）模拟技术,利用κ-ε湍流模型和离散坐标（DO）辐射模型,模拟自然通风条件下日光温室内空气相对湿度分布。结果表明：CFD能够较好地模拟自然通风条件下温室内湿度变化特征,湿度模拟值与实测值平均误差为5.5%;低风速条件下,自然通风降湿能力弱,温室内湿度呈现明显的下高上低的垂直分布,随着风速增大,降湿效果明显提高,温室内湿度呈现北侧湿度高南侧湿度低的分布特征;风向为温室自然通风降湿的主要动力因素,对降湿效果影响较大,风向为与温室建造走向一致的偏东风时,温室内湿度低且分布均匀,降湿效率高,北风时,温室内湿度空间差异大,降湿效果差。该研究可以为日光温室的结构优化设计和环境调控提供科学依据。     

Nationally Determined Contributions under the Paris Agreement and the costs of delayed action

Current country-level commitments under the Paris Agreement fall short of putting the world on a required trajectory to stay below a 2°C temperature increase compared to pre-industrial levels by the end of the century. Therefore, the timing of increased ambition is hugely important and as such this paper analyses the impact of both the short and long-term goals of the Paris Agreement on global emissions and economic growth. Using the hybrid TIAM-UCL-MSA model we consider the achievement of a 2°C target against a baseline of the Nationally Determined Contributions (NDCs) while also considering the timing of increased ambition of the NDCs by 2030 and the impacts of cost reductions of key low-carbon technologies. We find that the rate of emissions reduction ambition required between 2030 and 2050 is almost double when the NDCs are achieved but not ratcheted up until 2030, and leads to lower levels of economic growth throughout the rest of the century. However, if action is taken immediately and is accompanied by increasingly rapid low-carbon technology cost reductions, then there is almost no difference in GDP compared to the path suggested by the current NDC commitments.

Key policy insights

• Delaying the additional action needed to achieve the 2°C target until 2030 is shown to require twice the rate of emissions reductions between 2030 and 2050.

• Total cumulative GDP over the century is lower when additional action is delayed to 2030 and therefore has an overall negative impact on the economy, even without including climate change damages.

• Increased ratcheting of the NDC commitments should therefore be undertaken sooner rather than later, starting in conjunction with the 2023 Global Stocktake.

• Early action combined with cost reductions in key renewable energy technologies can reduce GDP losses to minimal levels (<1%).

• A 2°C future with technological advancements is clearly possible for a similar cost as a 3.3°C world without these advances, but with lower damages and losses from climate change.

     

部分国家长期温室气体低排放发展战略比较分析

面向21世纪中叶的长期低排放发展战略是继国家自主贡献之后,衡量各国长期减排努力的重要文件。文中针对已向《联合国气候变化框架公约》秘书处正式提交长期低排放发展战略的12个国家,从各国战略的总体结构、主要内容和实施面临的挑战等方面进行了比较分析。研究发现各国长期减排力度存在较大差别,分行业和分气体类型的减排目标分解仍较为初步,战略涉及的中长期减排目标与全球长期温升控制目标之间仍存在较大差距,长期减排政策措施的经济性尚不明确,并且对发展中国家的资金援助与需求间仍存在巨大缺口,这些问题均会严重制约长期低排放战略的后续有效实施。为推动中国长期战略的制订,文中从持续对各国战略跟踪分析、强化“两步走”战略安排下分阶段减排目标和任务分析研判、强化对战略路径特别是薄弱环节的梳理和拓展研究,以及加强对中国跨领域前瞻性相关重大战略问题的深入研究等4个方面提出了政策建议。     

全球气候变暖原因的争议

综合分析了政府间气候变化专门委员会(IPCC)与非政府间国际气候变化专门委员会(NIPCC)针锋相对的观点:是人类活动还是自然因素主导了过去近百年的气候变化.指出20世纪中期以来温度变化的事实支持人类活动影响的观点,但是在近百年中自然因素如太阳活动、火山活动或大洋热盐环流的变化,对温度的年代际变化有重要影响.有充分的古...