David W. Keith

Why Capture CO2 from the Atmosphere

Air capture is an industrial process for capturing CO2 from ambient air; it is one of an emerging set of technologies for CO2 removal that includes geological storage of biotic carbon and the acceleration of geochemical weathering. Although air capture will cost more than capture from power plants when both are operated under the same economic conditions, air capture allows one to apply industrial economies of scale to small and mobile emission sources and enables a partial decoupling of carbon capture from the energy infrastructure, advantages that may compensate for the intrinsic difficulty of capturing carbon from the air.

The effect of climate change on ozone depletion through changes in stratospheric water vapour

Several studies have predicted substantial increases in Arctic ozone depletion due to the stratospheric cooling induced by increasing atmospheric CO2 concentrations. But climate change may additionally influence Arctic ozone depletion through changes in the water vapour cycle. Here we investigate this possibility by combining predictions of tropical tropopause temperatures from a general circulation model with results from a one-dimensional radiative convective model, recent progress in understanding the stratospheric water vapour budget, modelling of heterogeneous reaction rates and the results of a general circulation model on the radiative effect of increased water vapour. Whereas most of the stratosphere will cool as greenhouse-gas concentrations increase, the tropical tropopause may become warmer, resulting in an increase of the mean saturation mixing ratio of water vapour and hence an increased transport of water vapour from the troposphere to the stratosphere. Stratospheric water vapour concentration in the polar regions determines both the critical temperature below which heterogeneous reactions on cold aerosols become important (the mechanism driving enhanced ozone depletion) and the temperature of the Arctic vortex itself. Our results indicate that ozone loss in the later winter and spring Arctic vortex depends critically on water vapour variations which are forced by sea surface temperature changes in the tropics. This potentially important effect has not been taken into account in previous scenarios of Arctic ozone loss under climate change conditions.

Research on global sun block needed now

Geoengineering studies of solar-radiation management should begin urgently, argue David W. Keith, Edward Parson and M. Granger Morgan — before a rogue state decides to act alone.

Relationship between traumatic events in childhood and chronic pain

PURPOSE The purpose was to examine the relationships between traumatic events in childhood, such as sexual and physical abuse, alcoholism, and drug addiction, and three types of chronic pain: facial pain, myofascial pain, and fibromyalgia. A fourth group, a heterogeneous group of other pain, was used as a comparison group. METHOD Ninety one patients with chronic pain, age range 20-60, were consecutively recruited from the outpatient clinics of a rehabilitation hospital and a general hospital. Patients were given four measures for completion at evaluation: Childhood History Questionnaire; Childhood Traumatic Events Scale; McGill Melzack Pain Questionnaire; Pain Disability Index. Chi-square was used to test significant differences among four pain groups on sexual, physical, and verbal abuse; alcoholism; drug dependence; medications; major upheaval, childhood illness, death of a family member or friend, and separation or divorce of parents. Logistic regression was used to predict membership in the four pain groups. RESULTS All pain groups had a history of abuse exceeding 48%: fibromyalgia, 64.7%; myofascial, 61.9%; facial, 50%; other pain, 48.3%. All groups had a history of family alcohol dependence exceeding 38%, and a history of drug dependence ranging from 5.8 to 19.1%. A combined history of pain, child physical abuse, and alcoholism was prevalent in 12.9 to 35.3%. Logistic regression showed patients who were female, with an alcoholic parent, using non-narcotic drugs were more likely to be members of the facial, myofascial, and fibromyalgia groups. CONCLUSIONS Child traumatic events are significantly related to chronic pain. Since the problem of child abuse is broader than physical and sexual abuse, health and rehabilitation agencies must shift from individualized treatment to interdisciplinary treatment of the family and patient.

A STRATEGY FOR INTRODUCING HYDROGEN INTO TRANSPORTATION

Considerable effort is being expended on research and demonstration projects aimed at introducing hydrogen into the transportation sector as a fuel, generally motivated by concerns about carbon dioxide emissions and petroleum imports (or scarcity). In this paper we focus on one aspect of strategy for introducing hydrogen—the choice of transportation mode.Our analysis suggests that cost of introducing hydrogen can be reduced by selecting a mode that uses a small number of relatively large vehicles that are operated by professional crews along a limited number of point-to-point routes or within a small geographic area.In addition, technological innovation in vehicle design will take place most quickly in modes where individual vehicles are produced to order and each receives significant engineering attention (not those manufactured in vast quantities on assembly lines).The immediate environmental benefits of introducing hydrogen fuel will occur in modes that have relatively less stringent pollution regulations applied to them.These insights, suggest that heavy-duty freight modes would be a less costly way to introduce hydrogen as a transportation fuel and a more effective way to advance hydrogen-related technologies so that they could subsequently be used more widely in light-duty vehicles. r 2002 Elsevier Science Ltd.All rights reserved.

Predicting PVT data for CO2-brine mixtures for black-oil simulation of CO2 geological storage

Accurate modeling of the storage or sequestration of CO2 injected into subsurface formations requires an accurate fluid model. This can be achieved using compositional reservoir simulations. However, sophisticated equations of state (EOS) approaches used in current compositional simulators are computationally expensive. It is advantageous and possible to use a simple, but accurate fluid model for the very specific case of geological CO2 storage. Using a black-oil simulation approach, the computational burden of flow simulation can be reduced significantly. In this work, an efficient and simple algorithm is developed for converting compositional data from EOS into black-oil PVT data. Our algorithm is capable of predicting CO2‐brine density, solubility, and formation volume factor, which are all necessary for black-oil flow simulations of CO2 storage in geological formations. Numerical simulations for asimple CO2storage case demonstrate that the black-oil simulationruns are atleast fourtimes fasterthan thecompositional oneswithout lossof accuracy. Theaccuracy in prediction of CO2‐brine black-oil PVT properties and higher computational efficiency of the black-oil approach promote application of black-oil simulation for large-scale geological storage of CO2 in saline aquifers.

A simple model to account for regional inequalities in the effectiveness of solar radiation management

We present a simple model to account for the potential effectiveness of solar radiation management (SRM) in compensating for anthropogenic climate change. This method provides a parsimonious way to account for regional inequality in the assessment of SRM effectiveness and allows policy and decision makers to examine the linear climate response to different SRM configurations. To illustrate how the model works, we use data from an ensemble of modeling experiments conducted with a general circulation model (GCM). We find that an SRM scheme optimized to restore population-weighted temperature changes to their baseline compensates for 99% of these changes while an SRM scheme optimized for population-weighted precipitation changes compensates for 97% of these changes. Hence, while inequalities in the effectiveness of SRM are important, they may not be as severe as it is often assumed.

Public understanding of solar radiation management

We report the results of the first large-scale international survey of public perception of geoengineering and solar radiation management (SRM). Our sample of 3105 individuals in the United States, Canada and the United Kingdom was recruited by survey firms that administer internet surveys to nationally representative population samples. Measured familiarity was higher than expected, with 8% and 45% of the population correctly defining the terms geoengineering and climate engineering respectively. There was strong support for allowing the study of SRM. Support decreased and uncertainty rose as subjects were asked about their support for using SRM immediately, or to stop a climate emergency. Support for SRM is associated with optimism about scientific research, a valuing of SRM’s benefits and a stronger belief that SRM is natural, while opposition is associated with an attitude that nature should not be manipulated in this way. The potential risks of SRM are important drivers of public perception with the most salient being damage to the ozone layer and unknown risks. SRM is a new technology and public opinions are just forming; thus all reported results are sensitive to changes in framing, future information on risks and benefits, and changes to context.

Analytical solution to evaluate salt precipitation during CO2 injection in saline aquifers

Abstract Carbon dioxide sequestration in deep saline aquifers is a means of reducing anthropogenic atmospheric emissions of CO 2 . Among various mechanisms, CO 2 can be trapped in saline aquifers by dissolution in the formation water. Vaporization of water occurs along with the dissolution of CO 2 . Vaporization can cause salt precipitation, which reduces porosity and impairs permeability of the reservoir in the vicinity of the wellbore, and can lead to reduction in injectivity. The amount of salt precipitation and the region in which it occurs may be important in CO 2 storage operations if salt precipitation significantly reduces injectivity. Here we develop an analytical model, as a simple and efficient tool to predict the amount of salt precipitation over time and space. This model is particularly useful at high injection velocities, when viscous forces dominate. First, we develop a model which treats the vaporization of water and dissolution of CO 2 in radial geometry. Next, the model is used to predict salt precipitation. The combined model is then extended to evaluate the effect of salt precipitation on permeability in terms of a time-dependent skin factor. Finally, the analytical model is corroborated by application to a specific problem with an available numerical solution, where a close agreement between the solutions is observed. We use the results to examine the effect of assumptions and approximations made in the development of the analytical solution. For cases studied, salt saturation was a few percent. The loss in injectivity depends on the degree of reduction of formation permeability with increased salt saturation. For permeability-reduction models considered in this work, the loss in injectivity was not severe. However, one limitation of the model is that it neglects capillary and gravity forces, and these forces might increase salt precipitation at the bottom of formation particularly when injection rate is low.

Cost analysis of stratospheric albedo modification delivery systems

We perform engineering cost analyses of systems capable of delivering 1‐5 million metric tonnes (Mt) of albedo modification material to altitudes of 18‐30 km. The goal is to compare a range of delivery systems evaluated on a consistent cost basis. Cost estimates are developed with statistical cost estimating relationships based on historical costs of aerospace development programs and operations concepts using labor rates appropriate to the operations. We evaluate existing aircraft cost of acquisition and operations, perform in-depth new aircraft and airship design studies and cost analyses, and survey rockets, guns, and suspended gas and slurry pipes, comparing their costs to those of aircraft and airships. Annual costs for delivery systems based on new aircraft designs are estimated to be