Projected impact of deep ocean carbon dioxide discharge on atmospheric CO2 concentrations

An evaluation of oceanic containment strategies for anthropogenic carbon dioxide is presented. Energy conservation is also addressed through an input hydrocarbon-fuel consumption function. The effectiveness of the proposed countermeasures is determined from atmospheric CO₂ concentration predictions. A previous box model with a diffusive deep ocean is adapted and applied to the concept of fractional CO₂ injection in 500 m deep waters. Next, the contributions of oceanic calcium carbonate sediment dissolution, and of deep seawater renewal, are included. Numerical results show that for CO₂ direct removal measures to be effective, large fractions of anthropogenic carbon dioxide have to be processed. This point favors fuel pre-processing concepts. The global model also indicates that energy conservation, i.e. a hydrocarbon-fuel consumption slowdown, remains the most effective way to mitigate the greenhouse effect, because it offers mankind a substantial time delay to implement new energy production alternatives.     

Interannual variation of atmospheric CO2 concentration

A method is described for the analysis of the interannual variability of background atmospheric carbon dioxide concentration. The analysis is carried out on the data from 6 observatories for which records of >8 years were available.A global-scale interannual variation of CO₂ concentration in the troposphere with a characteristic time-scale of 2–3 years has been confirmed throughout the period of the records. These variations are estimated to be associated with carbon cycle imbalances of 2–3 Gt or annual net exchanges between the atmosphere and another carbon reservoir(s) at a rate of about 1.2 Gt of carbon per year. Lag correlations and amplitude comparisons between the records suggests a low latitude southern hemisphere origin to this phenomenon.The interannual variations of CO₂ increase are found to be correlated with those observed in data for Pacific sea surface temperatures and Pacific witd stress, the Southern Oscillation Index and the Quasi-Biennial Oscillation. However multiple regression studies found that once the Southern Oscillation index is used as an explanatory variable for CO₂ variations, the inclusion of additional geophysical variables does not give any significant improvement in the regression.     

美国气候新政背景下的中国未来CO2排放情景预测

本文应用LMDI分解分析方法对中国2000—2014年生产部门CO₂排放量变化做因素分解分析,同时结合STIRPAT模型建立CO₂预测模型,分析2017—2030年中国的CO₂排放情况。结果表明,经济增长和能耗强度变化对中国CO₂排放量变化的影响分别为114.9%、-22.6%。基于预测模型变量构建未来情景,设定正常路线、减排路线和激进路线3条路线,共包含9种情景。正常路线的低碳情景和减排路线的基准情景下可实现2025年达到CO₂排放峰值,减排路线的低碳情景可实现2020年达到排放峰值。     

Siberian CO2 efflux in winter as a CO2 source and cause of seasonality in atmospheric CO2

Over three years, we found a consistent CO₂ efflux from forest tundra of the Russian North throughout the year, including a large (89 g C m^–2 yr^–1) efflux during winter. Our results provide one explanation for the observations that the highest atmospheric CO₂ concentration and greatest seasonal amplitude occur at high latitudes rather than over the mid-latitudes, where fossil fuel sources are large, and where high summer productivity offset by winter respiration should give large seasonal oscillations in atmospheric CO₂. Winter respiration probably contributed substantially to the boreal winter CO₂ efflux. Respiration is an exothermic process that produces enough heat to warm soils and promote further decomposition. We suggest that, as a result of this positive feedback, small changes in surface heat flux, associated with human activities in the North or with regional or global warming, could release large quantities of organic carbon that are presently stored in permafrost.     

景德镇地区大气CO2浓度变化特征

利用景德镇温室气体监测站CO_2观测数据,分析了景德镇地区2017年12月—2018年11月大气CO_2浓度变化特征,同时对其浓度进行了筛分,以剔除污染数据,使其更具区域代表性。研究表明:景德镇地区大气CO_2浓度昼降夜升,早上最高,傍晚最低;春季最高,秋季最低;春、夏季NNE、NE、ENE风向,秋季NE、ENE风向以及冬季W、WSW、SW、SSW、S风向上CO_2浓度较高。同时,春、夏和秋季大气CO_2浓度大致随风速的增加而不断降低,冬季风速对大气CO_2浓度无明显影响。筛分后数据显示景德镇地区年均大气CO_2浓度为422.1×10~(-6),浓度日均值年振幅73.96×10~(-6),夏半年CO_2浓度低于冬半年。     

基于统计学的中国典型大城市CO2排放达峰研究

对选取的36个中国典型大城市,分析2005—2019年直接CO2排放与总CO2排放特征,构建基于条件判断函数和Mann-Kendall趋势分析检验法的城市CO2排放达峰判断模型,判断36个城市排放是否达峰,并对达峰城市特征和处于不同排放阶段的典例城市进行深入分析.结果表明,36个典型大城市中,昆明、深圳与武汉3个城市已...     

Assessment of the biospheric contribution to surface atmospheric CO2 concentrations over East Asia with a regional chemical transport model

A regional chemical transport model, RAMS-CMAQ, was employed to assess the impacts of biosphere–atmosphere CO2 exchange on seasonal variations in atmospheric CO2 concentrations over East Asia. Simulated CO2 concentrations were compared with observations at 12 surface stations and the comparison showed they were generally in good agreement. Both observations and simulations suggested that surface CO2 over East Asia features a summertime trough due to biospheric absorption, while in some urban areas surface CO2 has a distinct summer peak, which could be attributed to the strong impact from anthropogenic emissions. Analysis of the model results indicated that biospheric fluxes and fossil-fuel emissions are comparably important in shaping spatial distributions of CO2 near the surface over East Asia. Biospheric flux plays an important role in the prevailing spatial pattern of CO2 enhancement and reduction on the synoptic scale due to the strong seasonality of biospheric CO2 flux. The elevation of CO2 levels by the biosphere during winter was found to be larger than 5ppm in North China and Southeast China, and during summertime a significant depletion( 7 ppm) occurred in most areas,except for the Indo-China Peninsula where positive bioflux values were found.     

选支CO激光86条发射谱线大气透过率的研究

本文给出了用实验方法得到的5.3—6.3微米范围内CO激光的86条谱线大气衰减系数的研究结果,简单地介绍了实验装置并对结果进行了讨论。分析表明,这一范围内的激光谱线在大气传输过程中主要受到水汽的衰减。各谱线大气衰减系数的实验值和相应的计算值之间存在着不同程度的差异,是由于水汽的共振吸收频率和激光发射频率之间的差异以及计算时采用Lorentz线型所引起的。在用CO激光监测大气微量气体或污染气体时,必须根据实际大气状况,进行必要的水汽订正。     

The effect of atmospheric CO2 and ice sheet topography on LGM climate

The role of reduced atmospheric CO₂ concentration and ice sheet topography plus its associated land albedo on the LGM climate is investigated using a coupled atmosphere-ocean-sea ice climate system model. The surface cooling induced by the reduced CO₂ concentration is larger than that by the ice sheet topography plus other factors by about 30% for the surface air temperature and by about 100% for the sea surface temperature. A large inter-hemispheric asymmetry in surface cooling with a larger cooling in the Northern Hemisphere is found for both cases. This asymmetric inter-hemispheric temperature response is consistent in the ice sheet topography case with earlier studies using an atmospheric model coupled with a mixed-layer ocean representation, but contrasts with these results in the reduced CO₂ case. The incorporation of ocean dynamics presumably leads to a larger snow and sea ice feedback as a result of the reduction in northward ocean heat transport, mainly as a consequence of the decrease in the North Atlantic overturning circulation by the substantial freshening of the North Atlantic convection regions. A reversed case is found in the Southern Ocean. Overall, the reduction in atmospheric CO₂ concentration accounts for about 60% of the total LGM climate change.     

Influence of traffic emissions on the composition of atmospheric particles of different sizes – Part 1: concentrations and elemental characterization

Epidemiological studies initially considered the impact of total solid particles on human health, but according to the acquired knowledge about the worse effect of smaller particles, those studies turned to consider the impact of PM₁₀. However, for the last decade PM_2.5 began to be more important, once as they are smaller they can penetrate deeper in the lungs, being possible their trapping in alveoli and worse effects on human health. Therefore, more information on PM_2.5 should be provided namely concerning the levels and elemental composition. Considering the relevance of traffic on the emission of particles of small sizes, this work included the detailed characterization of PM₁₀ and PM_2.5, sampled at two sites directly influenced by traffic, as well as at two reference sites, aiming a further evaluation of the influence of PM₁₀ and PM_2.5 on public health. The specific objectives were to study the influence of traffic emission on PM₁₀ and PM_2.5 characteristics, considering concentration, size distribution and elemental composition. PM₁₀ and PM_2.5 samples were collected using low-volume samplers; the element analyses were performed by particle induced X-ray emission (PIXE). At the sites influenced by traffic emissions PM₁₀ and PM_2.5 concentrations were 7–9 and 6–7 times higher than at the background sites. The presence of 17 elements (Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb) was determined in both PM fractions; particle metal contents were 3–44 and 3–27 times higher for PM₁₀ and PM_2.5, respectively, than at the backgrounds sites. The elements originated mostly from anthropogenic activities (S, K, V, Mn, Ni, Zn and Pb) were predominantly present in PM_2.5, while the elements mostly originated from crust (Mg, Al, Si and Ca) predominantly occurred in PM_2.5–10. The results also showed that in coastal areas sea salt spray is an important source of particles, influencing PM concentration and distributions (PM₁₀ increased by 46%, PM_2.5/PM₁₀ decreased by 26%), as well as PM compositions (Cl in PM₁₀ was 11 times higher).     

A sensitive method for measuring atmospheric concentrations of sulfur dioxide

A new sensitive method for measuring atmospheric concentrations of sulfur dioxide is presented. Samples are obtained using the mist chamber, which collects highly water-soluble gases with high efficiency, and concentrates them in a small volume of water. Particles are removed from the sampled air stream with a teflon filter, before it enters the mist chamber. After collection, the pH of the water is raised above pH 10 using sodium carbonate, then hydrogen peroxide (H₂O₂) is added to oxidize sulfur that may be present in the sulfur (IV) oxidation state, to sulfate. After a reaction time of at least 16 hours, the sulfate concentration is measured by ion chromatography. From the sulfate concentration, the water volume used in the mist chamber, and the volume of air sampled, the atmospheric concentration of SO₂ is computed. The method is not sensitive to other atmospheric sulfur gases such as DMS, SC₂, H₂S, COS, or MSH. The estimated overall precision of the method is 10%. The detection limit at the present stage of technique development is approximately 20 ppt (parts per trillion, or 10^-12 mol · mol^-1) for a 45 minute sampling time, with lower concentrations being detectable with lower precision.     

Summer dryness due to an increase of atmospheric CO2 concentration

To investigate the hydrologic changes of climate in response to an increase of CO₂-concentration in the atmosphere, the results from numerical experiments with three climate models are analyzed and compared with each other. All three models consist of an atmospheric general circulation model and a simple mixed layer ocean with a horizontally uniform heat capacity. The first model has a limited computational domain and simple geography with a flat land surface. The second model has a global computational domain with realistic geography. The third model is identical to the second model except that it has a higher computational resolution. In each numerical experiment, the CO₂-induced change of climate is evaluated based upon a comparison between the two climates of a model with normal and four times the normal concentration of carbon dioxide in air. It is noted that the zonal mean value of soil moisture in summer reduces significantly in two separate zones of middle and high latitudes in response to the increase of the CO₂-concentration in air. This CO₂-induced summer dryness results not only from the earlier ending of the snowmelt season, but also from the earlier occurrence of the spring to summer reduction in rainfall rate. The former effect is particularly important in high latitudes, whereas the latter effect becomes important in middle latitudes. Other statistically significant changes include large increases in both soil moisture and runoff rate in high latitudes of a model during most of the annual cycle with the exception of the summer season. The penetration of moisture-rich, warm air into high latitudes is responsible for these increases.     

The buffer capability of the ocean to increasing atmospheric CO2

The CO2-seawaler system and the method for calculating the partial pressure of CO2 (pCO3) in seawater are stu-died. The buffer capability of the ocean to increasing atmospheric CO2, is expressed in terms of the differential buffer factor and buffer index. Dissolutions of aragonite and calcite have a significant influence on the differential buffer factor. The trend of change in the buffer factor is obtained by a box model.     

Effect of ocean thermal diffusivity on global warming induced by increasing atmospheric CO2

A global mean ocean model including atmospheric heating, heat capacity of the mixed layer ocean, and vertical thermal diffusivity in the lower ocean, proposed by Cess and Goldenberg (1981), is used in this paper to study the sen-sitivity of global warming to the vertical diffusivity. The results suggest that the behaviour of upper ocean tempera-ture is mainly determined by the magnitude of upper layer diffusivity and an ocean with a larger diffusivity leads to a less increase of sea surface temperature and a longer time delay for the global warming induced by increasing CO2 than that with smaller one. The global warming relative to four scenarios of CO2 emission assumed by Intergovernmental Panel of Climate Change (IPCC) is also estimated by using the model with two kinds of thermal diffusivities. The result shows that for various combinations of the CO2 emission scenarios and the diffusivities, the oceanic time delay to the global warming varies from 15 years to 70 years.     

Estimates of UK CO2 emissions from aviation using air traffic data

The allocation of CO₂ emissions to specific sources is a major policy issue for international aviation, especially for determining allocations for emissions trading schemes. This paper addresses the problem by recommending a possible methodology to allocate emissions to specific sources using detailed air traffic data. The basis for the calculations is an air traffic sample for one full-day of traffic from the UK. In order to analyse aircraft fuel burn use and hence CO₂ emissions, the Reorganized Air Traffic Control Mathematical Simulator (RAMS Plus) and the Advanced Emission Model (AEM III) are used. The results from these detailed simulations are compared with two of the most widely-used aviation CO₂ emission estimates to have been made for the UK: the SERAS study and NETCEN estimate. Their estimates for the year 2000 are 26.1 and 31.4 Mt, respectively. In addition, the most recent NETCEN estimate for the year 2003 is 34.1 Mt of CO₂. Our estimate of total aviation CO₂ emissions, using detailed simulations and real air traffic data, is 34.7 Mt for the year 2004. In addition, emission estimates are compared with two global aviation emission inventories: AERO2K and SAGE. Contributions of the highest-emitting flights and aircraft types are identified. International departures dominate; 6% of flights account for 50% of total emissions. The largest aircraft emit the most per flight-km, although not per passenger-km. Different methodologies and their implications are also discussed.     

Constraining anthropogenic CH4 emissions in Nanjing and the Yangtze River Delta,China, using atmospheric CO2 and CH4 mixing ratios

Methane （CH4） emissions estimated with the Intergovernmental Panel on Climate Change （IPCC） inventory method at the city and regional scale are subject to large uncertainties.In this study,we determined the CH4：CO2 emissions ratio for both Nanjing and the Yangtze River Delta （YRD）,using the atmospheric CH4 and CO2 concentrations measured at a suburban site in Nanjing in the winter.The atmospheric estimate of the CH4：CO2 emissions ratio was in reasonable agreement with that calculated using the IPCC method for the YRD （within 20％）,but was 200％ greater for the municipality of Nanjing.The most likely reason for the discrepancy is that emissions from unmanaged landfills are omitted from the official statistics on garbage production.     

基于非线性分离的可倾转四旋翼LQR飞行控制研究

本文研究了一种能够独立控制位置和姿态的可倾转四旋翼飞行器,在建立了系统动力学模型的基础上,针对可倾转四旋翼飞行器系统存在的强输入非线性问题,采用了非线性分离策略,构造中间控制量,将该强非线性系统分离为线性动态环节和非线性静态环节,并仅针对线性动态环节设计了计算量小、易于硬件实现的线性二次型调节器（LQR）,然后再通过反解输入非线性环节将中间控制量分配到实际的控制量——旋翼倾转角和电机转速.仿真实验结果表明,基于非线性分离策略设计的LQR飞行控制器能够实现对可倾转四旋翼稳定控制,很好地独立追踪位置和姿态期望.     

基于车速依赖静态输出反馈的自主汽车路径跟踪控制

本文设计了一种新的基于静态输出反馈的增益调度控制器,可使自主汽车在车速时变且状态不全可测的情况下,完成路径跟踪并保证车身的横向稳定性.为了描述时变纵向速度对汽车动力学特性的影响,首先建立了一个包含跟踪特性及横向动力学特性的速度依赖多胞体汽车模型,同时,为减少控制器设计保守性,考虑时变参数之间非独立变化关系,采用了梯形多胞体进行描述;然后通过矩阵变换,获得系统性能描述,并基于增益调度控制策略及两步法,设计了满足H_∞性能的速度依赖静态输出反馈控制器,并给出其中参数求取方法,所提方法在实际应用中简单易行;最后在两种不同的典型道路上进行试验验证,仿真结果表明,在车速时变的情况下,所提控制方法可以有效控制自主汽车完成路径跟踪任务.     

The marginal impacts of CO2, CH4 and SF6 emissions

Abstract

A new version of the PAGE model, PAGE2002, has been used to calculate the marginal impacts of CO₂, CH₄ and SF₆ emissions based on Scenario A2 of the IPCC. The mean marginal impact of CO₂ is found to be US$19 per tonne of carbon (or about US$5 per tonne of CO₂), for methane it is US$105 per tonne, and for SF₆ it is US$200,000 per tonne. For each gas, the range between the 5% and 95% points is about an order of magnitude. The climate change impacts of methane are a significant proportion of its market price, and for SF₆ the climate change impacts are much larger than the market price. The economics of schemes to reduce the leakage of SF₆ are transformed once the climate change impacts are properly counted.