Comparative Assessment of Status and Opportunities for Carbon Dioxide Capture and Storage and Radioactive Waste Disposal in North America

Aside from the target storage regions being underground, geologic carbon sequestration (GCS) and radioactive waste disposal (RWD) share little in common in North America. The large volume of carbon dioxide (CO{sub 2}) needed to be sequestered along with its relatively benign health effects present a sharp contrast to the limited volumes and hazardous nature of high-level radioactive waste (RW). There is well-documented capacity in North America for 100 years or more of sequestration of CO{sub 2} from coal-fired power plants. Aside from economics, the challenges of GCS include lack of fully established legal and regulatory framework for ownership of injected CO{sub 2}, the need for an expanded pipeline infrastructure, and public acceptance of the technology. As for RW, the USA had proposed the unsaturated tuffs of Yucca Mountain, Nevada, as the region's first high-level RWD site before removing it from consideration in early 2009. The Canadian RW program is currently evolving with options that range from geologic disposal to both decentralized and centralized permanent storage in surface facilities. Both the USA and Canada have established legal and regulatory frameworks for RWD. The most challenging technical issue for RWD is the need to predict repository performance on extremely long time scales (10{sup 4}-10{sup 6} years). While attitudes toward nuclear power are rapidly changing as fossil-fuel costs soar and changes in climate occur, public perception remains the most serious challenge to opening RW repositories. Because of the many significant differences between RWD and GCS, there is little that can be shared between them from regulatory, legal, transportation, or economic perspectives. As for public perception, there is currently an opportunity to engage the public on the benefits and risks of both GCS and RWD as they learn more about the urgent energy-climate crisis created by greenhouse gas emissions from current fossil-fuel combustion practices

Solar geoengineering as part of an overall strategy for meeting the 1.5°C Paris target

Solar geoengineering refers to deliberately reducing net radiative forcing by reflecting some sunlight back to space, in order to reduce anthropogenic climate changes; a possible such approach would be adding aerosols to the stratosphere. If future mitigation proves insufficient to limit the rise in global mean temperature to less than 1.5°C above preindustrial, it is plausible that some additional and limited deployment of solar geoengineering could reduce climate damages. That is, these approaches could eventually be considered as part of an overall strategy to manage the risks of climate change, combining emissions reduction, net-negative emissions technologies and solar geoengineering to meet climate goals. We first provide a physical-science review of current research, research trends and some of the key gaps in knowledge that would need to be addressed to support informed decisions. Next, since few climate model simulations have considered these limited-deployment scenarios, we synthesize prior results to assess the projected response if solar geoengineering were used to limit global mean temperature to 1.5°C above preindustrial in an overshoot scenario that would otherwise peak near 3°C. While there are some important differences, the resulting climate is closer in many respects to a climate where the 1.5°C target is achieved through mitigation alone than either is to the 3°C climate with no geoengineering. This holds for both regional temperature and precipitation changes; indeed, there are no regions where a majority of models project that this moderate level of geoengineering would produce a statistically significant shift in precipitation further away from preindustrial levels.This article is part of the theme issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'

“Everyone has a peer in the low user tier”: the diversity of low residential energy users

Low residential energy use is typically associated with undesirable characteristics, such as poverty, thermal discomfort, or small dwelling size. The association of low energy use with deprivation has been an obstacle to promoting more aggressive goals for reduction of residential use. However, there is little research on the composition of the low user population. We investigated the demographics, behavior, and satisfaction of the lowest 10% of electricity consumers in Sacramento, CA, to see what attributes best correlated with low use. California, like many other regions, has GHG emissions goals requiring drastic reductions in residential consumption. Households in Sacramento’s lowest decile of electricity consumption already live at electricity consumption levels consistent with the goals for 2050. Our investigation of 700 of these households found that diversity of low users with regard to age, income, education, appliance ownership, and dwelling characteristics is similar to that of the general population. Low-use households tend to be smaller, but not enough to explain the entirety of low usage. Surveys and interviews revealed that those in the lowest 10% typically pursued low consumption deliberately and enthusiastically and were aware of their status as low users. Conversations about energy conserving strategies were embedded in their social lives. They employed diverse and creative strategies to maintain thermal comfort without excess energy use, often exceeding expert recommendations. Finally, the distribution of self-reported quality of life was no different from that of the general population living at much higher consumption levels. Overall, the key determinants of low use were a positive engagement with improvisation and experimentation, and the salience of energy in personal or social life. The population of low users should be treated as a valuable source of peer advice and lifestyle modeling