Impact of negative and positive CO2 emissions on global warming metrics using an ensemble of Earth system model simulations

The benefits of implementing negative emission technologies in the global warming response to cumulative carbon emissions until the year 2420 are assessed following the shared socioeconomic pathway (SSP) 1-2.6, the sustainable development scenario, with a comprehensive set of intermediate-complexity Earth system model integrations. Model integrations include 86 different model realisations covering a wide range of plausible climate states. The global warming response is assessed in terms of two key climate metrics: the effective transient climate response to cumulative CO2 emissions (eTCRE), measuring the surface warming response to cumulative carbon emissions and associated non-CO2 forcing, and the effective zero emissions commitment (eZEC), measuring the extent of any continued warming after net-zero CO2 emissions are reached. The transient climate response to cumulative CO2 emissions (TCRE) is estimated as 2.2 K EgC−1 (median value) with a 10 %–90 % range of 1.75 to 3.13 K EgC−1 in 2100, approximated from the eTCRE by removing the contribution of non-CO2 forcing. During the positive emission phase, the eTCRE decreases from 2.71 (2.0 to 3.65) to 2.61 (1.91 to 3.62) K EgC−1 due to a weakening in the dependence of radiative forcing on atmospheric carbon, which is partly opposed by an increasing fraction of the radiative forcing warming the surface as the ocean stratifies. During the net negative and zero emission phases, a progressive reduction in the eTCRE to 2.0 (1.39 to 2.96) K EgC−1 is driven by the reducing airborne fraction as atmospheric CO2 is drawn down mainly by the ocean. The model uncertainty in the slopes of warming versus cumulative CO2 emissions varies from being controlled by the radiative feedback parameter during positive emissions to being affected by carbon-cycle parameters during net negative emissions, consistent with the drivers of uncertainty diagnosed from the coefficient of variation of the contributions in the eTCRE framework. The continued warming after CO2 emissions cease and remain at zero gives a model mean eZEC of −0.03 K after 25 years, which decreases in time to −0.21 K at 90 years after emissions cease. However, there is a spread in the ensemble with a temperature overshoot occurring in 20 % of the ensemble members at 25 years after cessation of emissions. If net negative emissions are included, there is a reduction in atmospheric CO2 and there is a decrease in temperature overshoot so that the eZEC is positive in only 5 % of the ensemble members. Hence, incorporating negative emissions enhances the ability to meet climate targets and avoid risk of continued warming after net zero is reached

Management Strategies for Nitrate Removal from Water

Due to growing world population and expanding cities, comprehensive and integrated management of water resources and their utilization as a stable source become more important than before. Nitrate (NO3-) is one of the major sources of water pollution. It is one of the inorganic anions which obtain from nitrogen oxidation. This substance enters aquatic ecosystems through fertilizers, industrial waste, human and livestock sewage, acidic rain and excess nitrogen in the plant roots. Nitrogen compounds may cause many problems in surface water and groundwater. Various methods can be used to remove this pollutant, namely physical, chemical and biological methods which most of them are too expensive. The implementation of management strategies results in less need for work experts and leads to lower costs. In the present study we introduce management strategies and their effects

Study on effective processes in constructed wetland plants

Constructed wetlands are effective systems in wastewater treatment, improving storm water quality, flood control and groundwater recharge. Meanwhile plants, as one of the main components of wetlands, have the significant importance. In this research, biological and hydrodynamic processes of constructed wetlands related to plants were investigated. The study indicated that biological treatment through plants in wetland systems depends on plant type, root system and harvest season. In addition, investigation on the role of plants on hydrodynamic dispersion showed that their density and species (submerged or emerged), creation of different levels in wetland surface and morphological changes in depth impact on pollution dispersion

Study on variations of different elements concentration in rivers and their effective factors (case study: Zarrineh-Rud river)

Different factors affect concentration of dissolved substances in natural water systems. In the present study we investigated the discharge values and diverse substances concentration of Zarrineh-Rud river and compared them with theoretical values to find a pattern for discharge, salinity and concentration changes. For this purpose, quantitative and qualitative information of different stations of Zarrineh-Rud river were gained from Iran Water Resources Management Company. Among different stations we selected three of them. The comparison between actual values and the values obtained from linear, logarithmic and O’CONNOR model showed that the logarithmic model results have higher accuracy

Assessment of the influence of using waste steel fibres in improving concrete flexural strength

Considering the impact of using waste steel fibers in improving concrete mortar behavior especially its tensile strength and ductility, in this research the main effective features of these fibers including length to thickness ratio, geometry (with or without hook), material, strength and coherence to mortar were studied. In order to study on the fibers produced from welding and milling, they had to be categorized according to thickness, strength and width ranges. At first stage, contaminates such as grease were removed from fibers; then the cleaned fibers were cut into lengths of 3-4 cm, meaning that approximately 30% of the total waste were suitable for the experiment. In the experiments one specific mortar without any fiber was considered as an index. Other samples were made adding 1, 2, 3 and 5 of fiber weight percent to the mortar with properties similar to the index. Finally characteristics changes of the samples were determined through comparing with the index. Although experiment results indicated that using waste steel fibers leads to significant improvement in concrete flexural behavior, application of industrial fibers fabricated in the factory is still the first preference. This is mainly due to the possibility of producing industrial fibers with high quality materials and with uniform features especially tensile strength, length and thickness. On the other hand, quality control of material features of waste steel fibers is less than industrial fibers; thus the application of them is only recommended in low important structures and on a limited basis

The role of water-energy nexus in optimising water supply systems – Review of techniques and approaches

Considering water-energy nexus in optimising water supply systems not only ensures the sustainability of the water supply for increasing water demand but also diminishes water-related energy and environmental concerns. This paper presents a review highlighting knowledge gaps in optimisation models related to the water-energy nexus in water supply systems or “water supply side of the nexus”. Studies reported in the literature are categorised and systematically analysed in terms of different energy sources, centralised/ decentralised approaches and system parameters uncertainties. Several major gaps are identified. These include the lack of optimisation models capturing spatial aspects as well as environmental impacts of the nexus problems. The shortage of models considering uncertainties associated with water demand and renewable energy supply is another knowledge gap in this area. However, the main gap is the absence of models for optimising long-term planning of water supply system considering renewable energy within an urban context. Accordingly, based on this review, we have suggested pointers for future studies in the water supply side of the nexus

Reframing incentives for climate policy action

A key aim of climate policy is to progressively substitute renewables and energy efficiency for fossil fuel use. The associated rapid depreciation and replacement of fossil fuel-related physical and natural capital will entail a profound reorganisation of industry value chains, international trade, and geopolitics. Here, we present evidence confirming that the transformation of energy systems is well under way, and we explore the economic and strategic implications of the emerging energy geography. We show specifically that, given the economic implications of the ongoing energy transformation, the framing of climate policy as economically detrimental to those pursuing it is a poor description of strategic incentives. Instead, a new climate policy incentives configuration emerges where fossil fuel importers are better off decarbonising, competitive fossil fuel exporters are better off flooding markets, and uncompetitive fossil fuel producers – rather than benefitting from ‘free-riding’ – suffer from their exposure to stranded assets and lack of investment in decarbonisation technologies.BEIS (UK Gov) and the Children Investment Fund Foundation (CIFF

Substantial carbon drawdown potential from enhanced rock weathering in the United Kingdom

Achieving national targets for net-zero carbon emissions will require atmospheric carbon dioxide removal strategies compatible with rising agricultural production. One possible method for delivering on these goals is enhanced rock weathering, which involves modifying soils with crushed silicate rocks, such as basalt. Here we use dynamic carbon budget modelling to assess the carbon dioxide removal potential and agricultural benefits of implementing enhanced rock weathering strategies across UK arable croplands. We find that enhanced rock weathering could deliver net carbon dioxide removal of 6–30 MtCO2 yr−1 for the United Kingdom by 2050, representing up to 45% of the atmospheric carbon removal required nationally to meet net-zero emissions. This suggests that enhanced rock weathering could play a crucial role in national climate mitigation strategies if it were to gain acceptance across national political, local community and farm scales. We show that it is feasible to eliminate the energy-demanding requirement for milling rocks to fine particle sizes. Co-benefits of enhanced rock weathering include substantial mitigation of nitrous oxide, the third most important greenhouse gas, widespread reversal of soil acidification and considerable cost savings from reduced fertilizer usage. Our analyses provide a guide for other nations to pursue their carbon dioxide removal ambitions and decarbonize agriculture—a key source of greenhouse gases