The role of negative carbon emissions in reaching the Paris climate targets: The impact of target formulation in integrated assessment models

Global net-negative carbon emissions are prevalent in almost all emission pathways that meet the Paris temperature targets. In this paper, we generate and compare cost-effective emission pathways that satisfy two different types of climate targets. First, the common approach of a radiative forcing target that has to be met by the year 2100 (RF2100), and, second, a temperature ceiling target that has to be met over the entire period, avoiding any overshoot. Across two integrated assessment models (IAMs), we found that the amount of net-negative emissions - when global net emissions fall below zero - depends to a large extent on how the target is represented, i.e. implemented in the model. With a temperature ceiling (no temperature overshoot), net-negative emissions are limited and primarily a consequence of trade-offs with non-CO2 emissions, whereas net-negative emissions are significant for the RF2100 target (temperature overshoot). The difference becomes more pronounced with more stringent climate targets. This has important implications: more stringent near-term emission reductions are needed when a temperature ceiling is implemented compared to when an RF2100 target is implemented. Further, in one IAM, for our base case assumptions, the cost-effective negative carbon emissions (i.e. gross anthropogenic removals) do not depend to any significant extent on how the constraint is implemented, only, largely, on the ultimate stringency of the constraint. Hence, for a given climate target stringency in 2100, the RF2100 target and the temperature ceiling may result in essentially the same amount of negative carbon emissions. Finally, it is important that IAM demonstrate results for diverse ways of implementing a climate target, since the implementation has implications for the level of near-term emissions and the perceived need for net-negative emissions (beyond 2050)

The mutual dependence of negative emission technologies and energy systems

While a rapid decommissioning of fossil fuel technologies deserves priority, most climate stabilization scenarios suggest that negative emission technologies (NETs) are required to keep global warming well below 2 °C. Yet, current discussions on NETs are lacking a distinct energy perspective. Prominent NETs, such as bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS), will integrate differently into the future energy system, requiring a concerted research effort to determine adequate means of deployment. In this perspective, we discuss the importance of energy per carbon metrics, factors of future cost development, and the dynamic response of NETs in intermittent energy systems. The energy implications of NETs deployed at scale are massive, and NETs may conceivably impact future energy systems substantially. DACCS outperform BECCS in terms of primary energy required per ton of carbon sequestered. For different assumptions, DACCS displays a sequestration efficiency of 75–100%, whereas BECCS displays a sequestration efficiency of 50–90% or less if indirect land use change is included. Carbon dioxide removal costs of DACCS are considerably higher than BECCS, but if DACCS modularity and granularity helps to foster technological learning to <100$ per tCO2, DACCS may remove CO2 at gigaton scale. DACCS also requires two magnitudes less land than BECCS. Designing NET systems that match intermittent renewable energies will be key for stringent climate change mitigation. Our results contribute to an emerging understanding of NETs that is notably different to that derived from scenario modelling

The mutual dependence of negative emission technologies and energy systems

While a rapid decommissioning of fossil fuel technologies deserves priority, most climate stabilization scenarios suggest that negative emission technologies (NETs) are required to keep global warming well below 2 °C. Yet, current discussions on NETs are lacking a distinct energy perspective. Prominent NETs, such as bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS), will integrate differently into the future energy system, requiring a concerted research effort to determine adequate means of deployment. In this perspective, we discuss the importance of energy per carbon metrics, factors of future cost development, and the dynamic response of NETs in intermittent energy systems. The energy implications of NETs deployed at scale are massive, and NETs may conceivably impact future energy systems substantially. DACCS outperform BECCS in terms of primary energy required per ton of carbon sequestered. For different assumptions, DACCS displays a sequestration efficiency of 75–100%, whereas BECCS displays a sequestration efficiency of 50–90% or less if indirect land use change is included. Carbon dioxide removal costs of DACCS are considerably higher than BECCS, but if DACCS modularity and granularity helps to foster technological learning to <100$ per tCO2, DACCS may remove CO2 at gigaton scale. DACCS also requires two magnitudes less land than BECCS. Designing NET systems that match intermittent renewable energies will be key for stringent climate change mitigation. Our results contribute to an emerging understanding of NETs that is notably different to that derived from scenario modelling.TU Berlin, Open-Access-Mittel - 201

The contribution of Chinese exports to climate change

Within 5 years, China's CO2 emissions have nearly doubled, and China may already be the world's largest emitter of CO2. Evidence suggests that exports could be a main cause for the rise in Chinese CO2 emissions; however, no systematic study has analyzed this issue, especially over time. We find that in 2005, around one-third of Chinese emissions (1700 Mt CO2) were due to production of exports, and this proportion has risen from 12% (230 Mt) in 1987 and only 21% (760 Mt) as recently as 2002. It is likely that consumption in the developed world is driving this trend. A majority of these emissions have largely escaped the scrutiny of arguments over “carbon leakage” due to the current, narrow definition of leakage. Climate policies which would make the developed world responsible for China's export emissions have both benefits and costs, and must be carefully designed to achieve political consensus and equity. Whoever is responsible for these emissions, China's rapidly expanding infrastructure and inefficient coal-powered electricity system need urgent attention

1,2-Dimethyl-4,5-diphenyl­benzene determined on a Bruker SMART X2S benchtop crystallographic system

The title compound, C20H18, has two crystallographically independent mol­ecules in the asymmetric unit. The phenyl substituents of mol­ecule A are twisted away from the plane defined by the central benzene ring by 131.8 (2) and −52.7 (3)°. The phenyl substituents of mol­ecule B are twisted by −133.3 (2) and 50.9 (3)°. Each mol­ecule is stabilized by a pair of intra­molecular C(aryl, sp 2)—H⋯π inter­actions, as well as by several inter­molecular C(methyl, sp 3)—H⋯π inter­actions

Accounting for the climate-carbon feedback in emission metrics

Most emission metrics have previously been inconsistently estimated by including the climate-carbon feedback for the reference gas (i.e. CO2) but not the other species (e.g. CH4). In the fifth assessment report of the IPCC, a first attempt was made to consistently account for the climate-carbon feedback in emission metrics. This attempt was based on only one study, and therefore the IPCC concluded that more research was needed. Here, we carry out this research. First, using the simple carbon-climate model OSCAR v2.2, we establish a new impulse response function for the climate-carbon feedback. Second, we use this impulse response function to provide new estimates for the two most common metrics: Global Warming Potential (GWP) and Global Temperature change Potential (GTP). We find that, when the climate-carbon feedback is correctly accounted for, the emission metrics of non-CO2 species increase, but in most cases not as much as initially indicated by IPCC. We also find that, when the feedback is removed for both the reference and studied species, these relative metric values only have modest changes compared to when the feedback is included (absolute metrics change more markedly). Including or excluding the climate-carbon feedback ultimately depends on the user’s goal, but consistency should be ensured in either case

The cost of procuring deceased donor kidneys: Evidence from OPO cost reports 2013-2017

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154616/1/ajt15669_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154616/2/ajt15669.pd

Moving toward Net-Zero Emissions Requires New Alliances for Carbon Dioxide Removal

The 1.5 degrees C target will require removing at least some of the carbon dioxide (CO2) previously emitted. Knowledge on how this can be done has been increasing, though barriers remain concerning governance, policy, and acceptability. For the 26th session of the Conference of the Parties (COP26) to move beyond an academic debate on CO2 removal (CDR), a broader alliance of research and policy communities, industry, and the public is needed