Linking Mid-century Concentration Targets to Long-Term Climate Change Outcomes

We present a framework that could inform the choice of an interim (mid-21st century) target in the making of climate mitigation policy. The idea of interim targets for greenhouse gas concentration has been proposed previously as a way to bridge short- and long-term climate targets, address concerns about the rate of temperature change, and provide guidance in planning for energy infrastructure while scientific understanding improves and long-term climate goals are negotiated. Our analysis relates a wide range of mid-century equivalent CO2 (eCO2) concentrations to rates of temperature increase as well as total long-term temperature increases, accounts for uncertainties in the carbon cycle and the climate response (including climate sensitivity, ocean diffusivity, and aerosol forcing), and provides a rough measure of the economic feasibility of different emissions pathways. Our results show, for example, that for a roughly 50% likelihood of limiting long-term warming to 20C above the pre-industrial level, and with the constraint that global emissions should not have to be reduced by more than 2.5%/year, the mid-century concentration needs to remain below about 470 ppm eCO2 (including only the Kyoto gases and defined relative to a year 2000 baseline). For a roughly 83% likelihood of achieving the same temperature goal, the mid-century target needs to be about 440 ppm. These targets require that emissions between 2010 and 2050 average to approximately the current level and the 1990 level, respectively. Our framework illustrates how delay in emissions reductions in the near term forecloses options in the long term. Finally, we demonstrate how near-term reductions of CO2 from a particular source, deforestation, can significantly facilitate the achievement of long-term temperature goals

A scalar invariant and the local geometry of a class of static spacetimes

The scalar invariant, I, constructed from the "square" of the first covariant derivative of the curvature tensor is used to probe the local geometry of static spacetimes which are also Einstein spaces. We obtain an explicit form of this invariant, exploiting the local warp-product structure of a 4-dimensional static spacetime, $~^{(3)}\Sigma \times_{f} \reals$, where $^{(3)}\Sigma$ is the Riemannian hypersurface orthogonal to a timelike Killing vector field with norm given by a positive function, $f$ on $^{(3)}\Sigma$. For a static spacetime which is an Einstein space, it is shown that the locally measurable scalar, I, contains a term which vanishes if and only if $^{(3)}\Sigma$ is conformally flat; also, the vanishing of this term implies (a) $~^{(3)}\Sigma$ is locally foliated by level surfaces of $f$, $^{(2)}S$, which are totally umbilic spaces of constant curvature, and (b) $^{(3)}\Sigma$ is locally a warp-product space. Futhermore, if $^{(3)}\Sigma$ is conformally flat it follows that every non-trivial static solution of the vacuum Einstein equation with a cosmological constant, is either Nariai-type or Kottler-type - the classes of spacetimes relevant to quantum aspects of gravity.Comment: LaTeX, 13 pages, JHEP3.cls; The paper is completely rewritten with a new title and introduction as well as additional results and reference

WorkChoices, imageChoices and the marketing of new industrial relations legislation

This article takes a critical discourse approach to one aspect of the Australian WorkChoices industrial relations legislation: the government’s major advertisement published in national newspapers in late 2005 and released simultaneously as a 16-page booklet. This strategic move was the initial stage of one of the largest ‘information’ campaigns ever mounted by an Australian government, costing more than $AUD137 million. This article analyse the semiotic (visual and graphic) elements of the advertisement to uncover what these elements contribute to the message, particularly through their construction of both an image of the legislation and a portrayal of the Australian worker. We argue for the need to fuse approaches from critical discourse studies and social semiotics to deepen understanding of industrial relations phenomena such as the ‘hard sell’ to win the hearts and minds of citizens regarding unpopular new legislation

Equilibrium and Adverse Selection

The nature of equilibrium in markets with adverse selection evoked considerable interest following George Akerlof's famous paper on the market for lemons. Whereas Akerlof argued that markets with adverse selection may yield no equilibrium, Charles Wilson has argued that multiple equilibria may result. In this paper, it is shown that if the distribution of quality follows some standard distribution, then a unique equilibrium will result. In the (less plausible) context of multiple-equilibria, conditions are derived under which both buyers and sellers will prefer higher price-equilibria

An Overview of Atmospheric Features Over the Western North Atlantic Ocean and North American East Coast—Part 2: Circulation, Boundary Layer, and Clouds

The Western North Atlantic Ocean (WNAO) is a complex land-ocean-atmosphere system that experiences a broad range of atmospheric phenomena, which in turn drive unique aerosol transport pathways, cloud morphologies, and boundary layer variability. This work, Part 2 of a 2-part paper series, provides an overview of the atmospheric circulation, boundary layer variability, three-dimensional cloud structure, and precipitation over the WNAO; the companion paper (Part 1) focused on chemical characterization of aerosols, gases, and wet deposition. Seasonal changes in atmospheric circulation and sea surface temperature explain a clear transition in cloud morphologies from small shallow cumulus clouds, convective clouds, and tropical storms in summer, to stratus/stratocumulus and multilayer cloud systems associated with winter storms. Synoptic variability in cloud fields is estimated using satellite-based weather states, and the role of postfrontal conditions (cold-air outbreaks) in the development of stratiform clouds is further analyzed. Precipitation is persistent over the ocean, with a regional peak over the Gulf Stream path, where offshore sea surface temperature gradients are large and surface fluxes reach a regional peak. Satellite data show a clear annual cycle in cloud droplet number concentration with maxima (minima) along the coast in winter (summer), suggesting a marked annual cycle in aerosol-cloud interactions. Compared with satellite cloud retrievals, four climate models qualitatively reproduce the annual cycle in cloud cover and liquid water path, but with large discrepancies across models, especially in the extratropics. The paper concludes with a summary of outstanding issues and recommendations for future work. © 2021. American Geophysical Union. All Rights Reserved.6 month embargo; first published: 10 January 2021This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]