Eventual saturation of the climate–carbon cycle feedback studied with a conceptual model

A saturation of climate–carbon cycle feedback was found earlier in the simulations with the IAP RAS climate model of intermediate complexity. Here, this eventual saturation is interpreted by using a conceptual linearised coupled model. It is shown that this saturation is due to weak, logarithmic, dependence of the carbon dioxide radiative forcing on its atmospheric concentration. This eventual saturation leads to the non-monotonic behaviour of climate–carbon cycle parameter f   in time. If the time scale of the atmospheric CO₂${\text{CO}}_2$ build up is _tp$t_{\text{p}}$ then, starting from an initial equilibrium, f   approaches maximum in time ?_tp$?t_{\text{p}}$. Afterwards, climate–carbon cycle parameter decreases and eventually tends to unity. The time scale of the latter decrease is _t1=(1−5)_tp$t_1=(1-5)t_{\text{p}}$. A dependence of _tm$t_{\text{m}}$ and _t1$t_1$ on governing parameters of the conceptual model is studied. It is argued that an eventual saturation of the climate–carbon cycle feedback is expected to occur also in the other integrations of sufficient length with coupled climate–carbon cycle models.     

Urban expansion and its contribution to the regional carbon emissions: Using the model based on the population density distribution

The method is used for calculating regional urban area dynamics and the resulting carbon emissions (from the land-conversion) for the period of 1980 till 2050 for the eight world regions. This approach is based on the fact that the spatial distribution of population density is close to the two-parametric Γ-distribution [Kendall, M.G., Stuart, A., 1958. The Advanced Theory of Statistics, vol. 1.2. Academic Press, New York; Vaughn, R., 1987. Urban Spatial Traffic Patterns, Pion, London]. The developed model provides us with the scenario of urbanisation, based on which the regional and world dynamics of carbon emissions and export from cities, and the annual total urban carbon balance are estimated. According to our estimations, world annual emissions of carbon as a result of urbanisation increase up to 1.25 GtC in 2005 and begin to decrease afterwards. If we compare the emission maximum with the annual emission caused by deforestation, 1.36 GtC per year, then we can say that the role of urbanised territories (UT) in the global carbon balance is of a comparable magnitude. Regarding the world annual export of carbon from UT, we observe its monotonous growth by three times, reaching 505 MtC. The latter, is comparable to the amount of carbon transported by rivers into the ocean (196–537 MtC). The current model shows that urbanisation is inhibited in the interval 2020–2030, and by 2050 the growth of urbanised areas would almost stop. Hence, the total balance, being almost constant until 2000, then starts to decrease at an almost constant rate. By the end of the XXI century, the total carbon balance will be equal to zero, with the exchange flows fully balanced, and may even be negative, with the system beginning to take up carbon from the atmosphere, i.e., becomes a “sink”. The regional dynamics is somewhat more complex, i.e., some regions, like China, Asia and Pacific are being active sources of Carbon through the studied period, while others are changing from source to sink or continue to be neutral in respect the GCC.     

Modeling the carbon cycle of urban systems

Although more than 80% of carbon dioxide emissions originate in urban areas, the role of human settlements in the biosphere evolution and in global carbon cycling remains largely neglected. Understanding the relationships between the form and pattern of urban development and the carbon cycle is however crucial for estimating future trajectories of greenhouse gas concentrations in the atmosphere and can facilitate mitigation of climate change. In this paper I review state-of-the-art in modeling of urban carbon cycle. I start with the properties of urban ecosystems from the ecosystem theory point of view. Then I discuss key elements of an urban system and to which degree they are represented in the existing models. In conclusions I highlight necessity of including biophysical as well as human related carbon fluxes in an urban carbon cycle model and necessity of collecting relevant data.     

华北地区水资源及水安全问题的思考与研究

结合中国科学院知识创新工程项目“华北地区水循环与水资源安全”的研究工作,论述华北地区紧迫的水安全问题与反思,展望国际水科学研究前沿与热点问题,介绍中国科学院在变化环境下的水循环、农业节水和水资源安全研究的阶段成果和近期研究行动计划,提出中国北方特别是华北地区的水文水资源科学研究与发展的几点建议。目的是研讨未来中国北方特别是华北地区水资源安全国家需求中的长远发展的前沿性问题。     

Consequences of changed wetness on riverine nitrogen – human impact on retention vs. natural climatic variability

The HBV-N model was used for a scenario analysis of changes in nitrogen retention and transport caused by alterations of wetness due to land drainage, lowering of lakes, building of dams and climatic variability in a river basin in south-central Sweden (1885–1994). In general, dams were situated in locations more favourable for retention, compared to the lowered lakes. Rather modest conversions of water bodies only changed nitrogen transport by about 3%. The 180-times-larger increase of (mainly) tile-drained agricultural land had, according to simulations, increased the nitrogen transport by 17%, due to reduced retention. However, compared to human-induced alteration of the landscape N retention, the choice of 10-year periods of climatological data had the overriding effect on the calculated nitrogen transport. Weather-induced variations resulted in a 13% difference in nitrogen retention between various 10-year periods. When the model was driven by climatological data from the driest 10-year period (1905–1914), the estimated average annual load was only half of that obtained with climatological data from the wettest 10-year period (1975–1984). Electronic Publication     

温带亚高山针叶林土壤碳循环微生物群落的时空动态

选取参与碳固定的二磷酸羧化/加氧酶基因（cbbM）、有机碳降解的淀粉酶基因（amylase）和纤维素酶基因（cellulase）作为分子标记,用实时定量PCR方法对温带亚高山华北落叶松（Larix gmelinii var.principis-rupprechtii）林、白杄（Picea meyeri）林、青杄（P.wilsonii）林和油松（Pinus tabulaeformis）林土壤碳循环功能微生物类群丰度的时空动态开展研究.结果显示,总碳（TC）、总氮（TN）、总硫（TS）、有机质（OM）和有机碳（TOC）、pH值、铵态氮（NH₄⁺-N）、硝态氮（NO₃^--N）、过氧化氢酶、蔗糖酶和脲酶活性在4种森林土壤中都有不同程度的差异,且有显著的季节变化特征.高海拔华北落叶松林土壤TC、TN、TS、C/N、OM和TOC含量最高,而pH值最低.土壤TC、TN、亚硝态氮（NO₂^--N）含量、蔗糖酶和脲酶活性,与碳循环微生物类群的丰度呈极显著相关.土壤NO₃^--N含量与有机碳分解和固碳微生物类群的相对丰度显著相关;土壤C/N、NO₂^--N、pH值、OM、TOC、过氧化氢酶及脲酶活性,与降解易分解碳（labile C）和难分解碳（recalcitrant C）的微生物类群的相对丰度呈极显著相关.植被类型和季节变化共同影响土壤碳循环微生物类群的丰度,而季节变化是主导因素.植被和土壤环境因子通过调控微生物群落碳代谢功能类群的结构,影响森林土壤碳源-汇的平衡.     

滇东主要断裂带温泉CO_2成因浅析

通过对滇东主要断裂带上典型温泉的地质背景、环境条件、水化学及碳、氦稳定同位素分析,探讨这些温泉CO2释放的一般规律。分析表明滇东主要断裂带温泉具有特殊的碳来源,其CO2释放与沿小江断裂混杂第三纪煤层(褐煤)有关。     

Influence of driving cycles on exhaust emissions and fuel consumption of gasoline passenger car in Bangkok

The influence of different driving cycles on their exhaust emissions and fuel consumption rate of gasoline passenger car was investigated in Bangkok based on the actual measurements obtained from a test vehicle driving on a standard chassis dynamometer. A newly established Bangkok driving cycle (BDC) and the European driving cycle (EDC) which is presently adopted as the legislative cycle for testing automobiles registered in Thailand were used. The newly developed BDC is constructed using the driving characteristic data obtained from the real on-road driving tests along selected traffic routes. A method for selecting appropriate road routes for real driving tests is also introduced. Variations of keyed driving parameters of BDC with different driving cycles were discussed. The results showed that the HC and CO emission factors of BDC are almost two and four times greater than those of EDC, respectively. Although the difference in the NOx emission factor is small, the value from BDC is still greater than that of EDC by 10%. Under BDC, the test vehicle consumes fuel about 25% more than it does under EDC. All these differences are mainly attributed to the greater proportion of idle periods and higher fluctuations of vehicle speed in the BDC cycle. This result indicated that the exhausted emissions and fuel consumption of vehicles obtained from tests under the legislative modal-type driving cycle (EDC) are significantly different from those actually produced under real traffic conditions especially during peak periods.     

中国NOx控制制度研究

中国NOx污染呈现总量逐年增加的趋势,已成为大气污染治理的主要内容.从NOx的控制制度、排放指标上对我国现行NOx控制体系进行了分析,并对我国进一步完善NOx控制制度及标准提出了建议.主要建议有(1)降低NOx控制标准适应当前环境状况;(2)应用科学方法,制订合理的NOx总量控制标准和制度;(3)制订氮氧化物排放标准;(4)浓度控制和总量控制结合.总量控制的实施要注意污染物排放标准制定的政策取向;总量控制法的基本原理和程序;总量控制结合排放标准控制.     

中国农田肥料N2O直接和间接排放重新评估

农田肥料(氮肥、复合肥、有机肥)是我国N₂O最大的排放源,其估计直接决定了排放总量的可靠性.为此,重新评估了中国农田肥料N₂O的直接和间接排放,选择2008年县域尺度活动数据、具有空间分异性的本土排放因子和参数来重新评估其排放规模、结构、空间格局及不确定性;通过与IPCC、EDGAR等国内外研究结果的对比分析,阐述该排放清单的可靠性和全面性.结果表明,2008年我国农田肥料N₂O排放总量为617.1 Gg(处于213.7~1149.2 Gg之间),其中,氮肥直接排放为458.8 Gg(74.5%),有机肥直接排放为121.0 Gg(19.6%),挥发沉降和淋溶径流造成的间接排放分别为28.0 Gg(4.5%)和9.3 Gg(仅占1.5%左右).排放集中在华北平原、东北的松辽平原、华中的淮河流域和四川盆地,以及华南的珠三角、雷州半岛和台湾地区的县(区、市、旗),主要分布在江苏(52.4 Gg)、四川(48.0 Gg)、湖北(43.2 Gg)、广东(40.8 Gg)、河南(39.6 Gg)、安徽(38.4 Gg)、湖南(31.6 Gg)、山东(28.9 Gg),其累积规模为全国总量的52%,其中,近50%的贡献源于164个县(区、市、旗).本排放清单具有更高的准确度和空间分辨率,而基于IPCC (2006)排放因子及参数的估计排放总量高估了约8.3%,对直接排放和间接排放则分别低估了12.5%和高估了330%.此外,在空间格局上还表现出高值区低估和低值区高估的特点,在491和1225个县(区、市、旗)的相对偏差超过了100%和50%,特别指出的是,间接排放在大部分县(区、市、旗)的相对偏差达到135%左右.