A quantum mechanical charge field (QMCF) molecular dynamics (MD) study of Pb(II) in an aqueous medium was carried out in order to gain insight into its solvation behavior, for both structural and dynamic aspects. Applying the advanced methodology and different basis sets, some new aspects concerning the solvation of Pb(II) have been revealed. One of the most interesting outcomes of the current simulation is the variation of first shell coordination number from 7 to 9 in the Pb(H2O)n(2+) complex with Pb(H2O)8(2+) as a major species. Moreover, a far more dynamic and labile hydration shell was found compared to previous QM/MM MD simulation with only the first hydration shell treated by quantum mechanics, which reported a very rigid first hydration shell with a fixed coordination number of 9. The current simulation results are in much better agreement with the properties reported from the recent thermodynamic studies than the previous QM/MM MD study.
From typhoons to wildfires, as the visible impacts of climate change mount, calls for mitigation through carbon drawdown are escalating. Environmentalists and many climatologists are urging steps to enhance biological methods of carbon drawdown and sequestration. Market actors seeing avenues for profit have launched ventures in mechanical–chemical carbon dioxide removal (CDR), seeking government support for their methods. Governments are responding. Given the strong, if often unremarked, momentum of demands for public subsidy of these commercial methods, on what cogent bases can elected leaders make decisions that, first and foremost, meet societal needs? To address this question, we reviewed the scientific and technical literature on CDR, focusing on two methods that have gained most legislative traction: point-source capture and direct air capture–which together we term “industrial carbon removal” (ICR), in contrast to biological methods. We anchored our review in a standard of “collective biophysical need,” which we define as a reduction of the level of atmospheric CO2. For each ICR method, we sought to determine (1) whether it sequesters more CO2 than it emits; (2) its resource usage at scale; and (3) its biophysical impacts. We found that the commercial ICR (C-ICR) methods being incentivized by governments are net CO2 additive: CO2 emissions exceed removals. Further, the literature inadequately addresses the resource usage and biophysical impacts of these methods at climate-significant scale. We concluded that dedicated storage, not sale, of captured CO2 is the only assured way to achieve a reduction of atmospheric CO2. Governments should therefore approach atmospheric carbon reduction as a public service, like water treatment or waste disposal. We offer policy recommendations along this line and call for an analysis tool that aids legislators in applying biophysical considerations to policy choices.
This work is a product of the staff of The World Bank with external contributions. The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent.The World Bank does not guarantee the accuracy, completeness, or currency of the data included in this work and does not assume responsibility for any errors, omissions, or discrepancies in the information, or liability with respect to the use of or failure to use the information, methods, processes, or conclusions set forth. The boundaries, colors, denominations, and other information shown on any map in this work do not imply any judgment on the part of The World Bank concerning the legal status of any territory or the endorsement or acceptance of such boundaries.Nothing herein shall constitute or be construed or considered to be a limitation upon or waiver of the privileges and immunities of The World Bank, all of which are specifically reserved.
The green bond market is emerging as an impactful financing mechanism in climate change mitigation efforts. The effectiveness of the financial market for this transition to a low-carbon economy depends on attracting investors and removing financial market roadblocks. This paper investigates the differential bond performance of green vs non-green bonds with (1) a dynamic portfolio model that integrates negative as well as positive externality effects and via (2) econometric analyses of aggregate green bond and corporate energy time-series indices; as well as a cross-sectional set of individual bonds issued between 1 January 2017, and 1 October 2020. The asset pricing model demonstrates that, in the long-run, the positive externalities of green bonds benefit the economy through positive social returns. We use a deterministic and a stochastic version of the dynamic portfolio approach to obtain model-driven results and evaluate those through our empirical evidence using harmonic estimations. The econometric analysis of this study focuses on volatility and the risk–return performance (Sharpe ratio) of green and non-green bonds, and extends recent econometric studies that focused on yield differentials of green and non-green bonds. A modified Sharpe ratio analysis, cross-sectional methods, harmonic estimations, bond pairing estimations, as well as regression tree methodology, indicate that green bonds tend to show lower volatility and deliver superior Sharpe ratios (while the evidence for green premia is mixed). As a result, green bond investment can protect investors and portfolios from oil price and business cycle fluctuations, and stabilize portfolio returns and volatility. Policymakers are encouraged to make use of the financial benefits of green instruments and increase the financial flows towards sustainable economic activities to accelerate a low-carbon transition.
Carbon dioxide removal (CDR) has become a focal point for legislators and policymakers who are pursuing strategies for climate change mitigation. This paper employs a policy framework of collective biophysical need to examine two broad categories of CDR methods being subsidized and advanced by the United States and other countries: mechanical capture and biological sequestration. Using published data on these methods, we perform a biophysical input-outcome analysis, focusing on the U.S., and compare methods on the basis of three criteria: effectiveness at net carbon removal, efficiency at a climate-relevant scale, and beneficial and adverse co-impacts. Our findings indicate that biological methods have a superior return on resource inputs in comparison to mechanical methods. Biological methods are both more effective and more resource efficient in achieving a climate-relevant scale of CO2 removal. Additionally, the co-impacts of biological methods are largely positive, while those of mechanical methods are negative. Biological methods are also far less expensive. Despite their disadvantages and a track record of failure to date, mechanical CDR methods continue to receive large subsidies from the US government while biological sequestration methods do not. To achieve more optimal CDR outcomes, policymakers should evaluate CDR methods’ effectiveness, efficiency, and biophysical co-impacts. We present tools for this purpose.
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