Effects of solar radiation modification on the ocean carbon cycle: An earth system modeling study

Solar radiation modification (SRM, also termed as geoengineering) has been proposed as a potential option to counteract anthropogenic warming. The underlying idea of SRM is to reduce the amount of sunlight reaching the atmosphere and surface, thus offsetting some amount of global warming. Here, the authors use an Earth system model to investigate the impact of SRM on the global carbon cycle and ocean biogeochemistry. The authors simulate the temporal evolution of global climate and the carbon cycle from the pre-industrial period to the end of this century under three scenarios: the RCP4.5 CO₂ emission pathway, the RCP8.5 CO₂ emission pathway, and the RCP8.5 CO₂ emission pathway with the implementation of SRM to maintain the global mean surface temperature at the level of RCP4.5. The simulations show that SRM, by altering global climate, also affects the global carbon cycle. Compared to the RCP8.5 simulation without SRM, by the year 2100, SRM reduces atmospheric CO₂ by 65 ppm mainly as a result of increased CO₂ uptake by the terrestrial biosphere. However, SRM-induced change in atmospheric CO₂ and climate has a small effect in mitigating ocean acidification. By the year 2100, relative to RCP8.5, SRM causes a decrease in surface ocean hydrogen ion concentration ([H⁺]) by 6% and attenuates the seasonal amplitude of [H⁺] by about 10%. The simulations also show that SRM has a small effect on globally integrated ocean net primary productivity relative to the high-CO₂ simulation without SRM. This study contributes to a comprehensive assessment of the effects of SRM on both the physical climate and the global carbon cycle.摘要太阳辐射干预地球工程是应对气候变化的备用应急措施. 其基本思路是通过减少到达大气和地表的太阳辐射, 从一定程度上抵消温室效应引起的全球变暖. 本研究使用地球系统模式模拟理想化太阳辐射干预方法对海洋碳循环的影响. 模拟试验中, 通过直接减少太阳辐射将RCP8.5 CO₂排放情景下的全球平均温度降低到RCP4.5情景下的温度. 模拟结果表明, 到2100年, 相对于RCP8.5情景, 减少太阳辐射通过增加陆地碳汇, 使大气CO₂浓度降低了65 ppm. 减少太阳辐射对海洋酸化影响很小. 到 2100 年, 相对于RCP8.5情景, 减少太阳辐射使海表平均氢离子浓度减少6%, pH上升0.03, 同时使海表平均氢离子浓度的季节变化振幅衰减约10%. 模拟结果还表明, 减少太阳辐射对全球海洋净初级生产力的影响较小. 本研究有助于深化我们对太阳辐射干预地球工程的气候和碳循环效应的认知和综合评估.     

碳中和目标下中国燃煤电厂CCUS集群部署优化研究

燃煤电厂作为中国最大的CO₂排放源,是中国实现碳中和目标的关键点。CO₂捕集、利用与封存（CCUS）技术是目前煤电行业实现深度减排的唯一途径,碳约束情景下,CCUS技术将在实现煤电碳达峰、碳中和目标中发挥不可或缺的作用。研究中首先使用综合环境控制模型（IECM）对燃煤电厂捕集技术环节的成本构成和经济性进行核算,得到中国燃煤电厂逐厂CO₂捕集成本和捕集量;其次,基于地质利用封存潜力及分布特征,构建CCUS源汇匹配优化模型,得到碳中和目标下的煤电CCUS项目分阶段布局方案;最后,以优化基础设施建设并通过规模经济降低成本为前提,使用聚类分析方法对煤电CCUS项目集群进行识别,进一步构建改进成本最小生成树模型,得到CCUS项目集群最低成本CO₂输送管道网络的路线优化策略。研究表明：碳中和目标约束下,需要对总装机容量约为355 GW的300个燃煤电厂进行CCUS技术改造,2030—2060年间可实现累积减排190.11 亿t CO₂。煤电CCUS项目集群主要分布在华中、华北和西北地区,通过建立CCUS枢纽以实现CO₂运输基础设施共享,在松辽盆地、渤海湾盆地、苏北盆地和鄂尔多斯盆地优先开展CCUS早期集成示范项目,能显著降低运输成本,推动CCUS技术大规模、商业化发展。     

基于飞行阶段的精细化航空二氧化碳排放因子研究

航空运输是交通领域CO₂排放增长最快速的部门。文中选择中国民航使用频率较高的超大型、大型、中型和小型飞机的典型机型,基于不同飞机在起飞、爬升、巡航、接近和滑行阶段引擎油耗速率、运行时间和油耗量的变化,计算航空飞机CO₂排放因子。同时结合各机型碳排放因子、额定载客量与客座率评估旅客搭乘不同飞机时的人均CO₂排放量（即单位客运周转量CO₂排放因子)。结果显示,超大型飞机、大型飞机、中型飞机和小型飞机在其航程区间内的平均CO₂排放因子分别为49.8、31.7、16.2和8.5 kg CO₂/km;满载条件下单位客运周转量CO₂排放因子均值分别为102.6、95.2、81.7和112.4 g CO₂/(人∙km)。起飞和爬升阶段引擎油耗速率约为巡航阶段油耗速率的2.6~3.4倍和2.0~2.8倍,飞机CO₂排放因子随飞行里程的提高而降低。航空运输是高碳客运方式,相同里程条件下,航空单位客运周转量CO₂排放因子显著高于高铁、道路机动车等其他客运方式。提升燃油效率、减少短途航运、合理安排航线以提高客座率并减少中途转机是降低航空碳排放量的有效途径。     

Interpretation of IPCC AR6 report on carbon capture,utilization and storage (CCUS) technology development北大核心CSCD

近年来,碳捕集利用与封存(CCUS)作为减缓气候变化的关键技术之一,得到国际社会广泛关注。政府间气候变化专门委员会(IPCC)第六次评估报告(AR6)第三工作组报告对CCUS进行了重新定位,并围绕减排潜力、减排成本、综合效益及应用前景等方面,对CCUS相关技术进行了系统全面评估。结论显示,CCUS技术是全球气候目标实现不可或缺的减排技术组合,到21世纪中叶有潜力实现累积千亿吨级减排效应,但当前CCUS技术成熟度整体处于示范阶段,成本较高,减排潜力有待进一步释放。综合考虑CCUS可以有效降低巨额资产搁浅风险、具有良好社会环境效益等因素,我国应结合自身“富煤、贫油、少气”的资源禀赋和基本国情,将CCUS作为战略性技术,统筹政策顶层设计、加速技术体系构建、探索市场激励机制、加强国际科技合作,促进CCUS技术发展。     

国土空间总体规划温室气体核算模型

城市的低碳发展对于应对气候变化及实现我国“碳达峰、碳中和”目标起着至关重要的作用。在新的国土空间规划体系下,国土空间总体规划对城市的低碳发展影响重大。为解决现有的城市温室气体核算中存在的问题,使总体规划促进城市低碳发展,构建了国土空间总体规划温室气体核算模型。该模型基于“空间布局—用地类型—部门划分—模型方法”的框架,采用自上而下与自下而上相结合的方法,与国土空间规划要素紧密结合;建立了市域和中心城区两个层次的碳排放核算方法,并解决了中心城区的碳排放核算问题,可进行国际间比较;解决了总体规划能源预测不完善的问题,提出了不同的核算方法供灵活选择,与完全基于用地类型的方法相比,降低了不确定性。最后基于模型提出了评估总体规划低碳发展水平的核心指标与参考指标。     

A Holocene record of Neotropical savanna dynamics from El Salvador

The historical ecology of the Ahuachapan savanna is reconstructed from a 4.83-m sediment core from Laguna Llano del Espino, Ahuachapan, western El Salvador. Stable carbon isotopes (¹³C), pollen, and charred grass cuticles indicate Holocene grassland dominance from at least ca. 3300 cal yr B.P. to the present. The role of people in the creation and maintenance of Central American savannas is considered in light of the paleoecological record. The data suggest that pre-Columbian inhabitants of western El Salvador suppressed shrub and tree encroachment via frequent burning from ca. 2500 to 500 cal yr. B.P. A substantial increase in woody taxa (Mimosoideae, Urticales) and a decrease in biomass burning are evident in the pollen and charcoal records beginning around the time of the first European contact (ca 500 cal yr B.P.). Evidence for frequent burning and grassland dominance before the arrival of the Europeans, followed by shrub and tree encroachment amid a near absence of fire after contact, suggests that the openness of the Ahuachapan savanna was maintained by the pre-Columbian inhabitants of the Rio Paz Valley throughout the late Holocene.     

Characteristics of <Emphasis Type="Italic">p</Emphasis>CO<Subscript>2</Subscript> in surface water of the Bering Abyssal Plain and their effects on carbon cycle in the

Characteristics of the pCO₂ distribution in surface water of the Bering Abyssal Plain and their relationships with the ambient hydrological conditions were discussed using variations of the partial pressure of CO₂ in surface water of the Bering Abyssal Plain and the Chukchi Sea. Data in this study are from a field investigation during the First Chinese National Arctic Research Expedition in 1999. Compared to the high productivity in the Bering Continental Shelf, much lower levels of chlorophyll a were observed in the Bering Abyssal Plain. The effect of hydrological factors on the pCO₂ distribution in surface seawater of the Plain in summer has become a major driving force and dominated over biological factors. The Plain also presents a High Nutrient Low Chlorophyll (HNLC). In addition, the pCO₂ distribution in the Bering Abyssal Plain has also been found to be influenced from the Bering Slope Current which would transform to the Anadyr Current when it inflows northwestward over the Plain. The Anadyr Current would bring a high nutrient water to the western Arctic Ocean where local nutrients are almost depleted in the surface water during the summer time. Resupplying nutrients would stimulate the growth of phytoplankton and enhance capacity of absorbing atmospheric CO₂ in the surface water. Otherwise, in the Bering Sea the dissolved inorganic carbon brought from freshwater are not deposited down to the deep sea water but most of them would be transported into the western Arctic Ocean by the Alaska Coastal Current to form a carbon sink there. Therefore, the two carbon sinks in the western Arctic Ocean, one carried by the Anadyr Current and another by the Alaska Costal Current, will implicate the western Arctic Ocean in global change.     

Invasion of anthropogenic CO<Subscript>2</Subscript> recorded in planktonic foraminifera from the northern Gulf of Aqaba

The stable carbon isotopic composition of the planktonic foraminifera Globigerinoides sacculifer and G. ruber (white) and sedimentary organic matter from the northern Gulf of Aqaba have been investigated to estimate changes in ¹³C_DIC in surface waters during the last 1,000 years. The high sedimentation rates at the core sites (about 54 cm/Kyear) provide high temporal resolution (~10 years). Recent sediments at the top of the cores reflect conditions younger than 1950. The ¹³C records of the planktonic foraminifera from three multicores display similar trends, showing a uniform and consistent pattern before the 1750s, and a gradual decrease of approximately 0.63 over the last two centuries. This decrease seems to track the decrease of ¹³C_DIC in surface waters, which is mainly caused by the increase of anthropogenic input of ¹³C-depleted CO₂ into the atmosphere. Similarly, a trend towards lighter values of the carbon isotopic composition of sedimentary organic matter (¹³C_org) during the last 200 years supports the interpretation obtained from the planktonic foraminiferal ¹³C. Furthermore, direct measurements of seawater show that ¹³C of the dissolved inorganic carbon (DIC) in the northern Gulf of Aqaba has decreased by about 0.44 during the period 1979–2000. The average annual decrease is 0.021, which is similar to that observed globally. The ¹³C values of planktonic foraminifera combined with organic matter ¹³C from marine sediments are good indicators for reconstructing past changes in atmospheric CO₂ concentrations from the northern Gulf of Aqaba.     

Geochemical and isotopic (Sr,C, O) data from the alkaline complex of Grønnedal-ĺka (South Greenland): evidence for unmixing and crustal contamination

The alkaline intrusion of Grønnedal-ka (South Greenland) is the oldest of the ten major rift-related plutonic complexes of southern Greenland that intruded during the Gardar period between 1330 and 1150 Ma into the 2.6-Ga-old gneisses and metasediments of the Ketilidian basement. The Grønnedal-ka alkaline intrusion consists of carbonatites, silicocarbonatites, transitional carbonatites and nepheline-bearing syenites. The silicocarbonatites exhibit locally ocellar textures that are typical for immiscibility processes. A ⁸⁷Sr/⁸⁶Sr initial ratio of about 0.703184 major and trace element compositions—including REE and C-, and O-isotope data from 15 carbonatite, 12 silicocarbonatite, 10 transitional carbonatite and 8 syenite and samples—provide evidence for minor crustal contamination of the mantle-derived magma that generated by unmixing carbonatites, silicocarbonatites and syenites. A scatter in major and trace element contents and isotope ratios is related to late- to post-magmatic alteration processes. The Grønnedal-ka silicocarbonatites are one of the rather rare cases in which unmixing of a highly alkaline mantle-derived magma into an alkalisilicate and a carbonatitic magma-fraction under plutonic conditions is well documented by textural and geochemical data.