Economic impacts of melting of the Antarctic Ice Sheet

Melting of the Antarctic Ice Sheet (AIS) could contribute metres to global sea level rise (SLR) in the long run. We couple models of AIS melting due to rising temperatures, SLR, and economic impacts of SLR on coastlines worldwide. We report SLR projections close to the latest literature. Coastal impacts of AIS melting are very heterogeneous: they are large as a share of GDP in one to two dozen countries, primarily Small Island Developing States. Costs can be reduced dramatically by economically efficient, proactive coastal planning: relative to a no adaptation scenario, optimal adaptation reduces total costs by roughly an order of magnitude. AIS melting increases the social cost of carbon by an expected 7% on low to medium emissions scenarios and with moderate discounting. There is a tail risk of very large increases in the social cost of carbon, particularly on a high emissions scenario

A Nozzle Analysis of Slow-Acceleration Solutions in One-Dimensional Models of Rotating Hot-Star Winds

We analyze the steady 1D flow equations for a rotating stellar wind based on a ``nozzle'' analogy for terms that constrain the local mass flux. For low rotation, we find the nozzle minimum occurs near the stellar surface, allowing a transition to a standard, CAK-type steep-acceleration solution; but for rotations > 75% of the critical rate, this inner nozzle minimum exceeds the global minimum, implying near-surface supercritical solutions would have an overloaded mass loss rate. In steady, analytic models in which the acceleration is assumed to be monotonically positive, this leads the solution to switch to a slow acceleration mode. However, time-dependent simulations using a numerical hydrodynamics code show that, for rotation rates 75 - 85% of critical, the flow can develop abrupt "kink" transitions from a steep acceleration to a decelerating solution. For rotations above 85% of critical, the hydrodynamic simulations confirm the slow acceleration, with the lower flow speed implying densities 5 - 30 times higher than the polar (or a nonrotating) wind. Still, when gravity darkening and 2D flow effects are accounted for, it seems unlikely that rotationally modified equatorial wind outflows could account for the very large densities inferred for the equatorial regions around B[e] supergiants.Comment: Accepted for publication in the Astrophysical Journal. 13 pages, 9 figure

Solar Magnetic Flux Tube Simulations with Time-Dependent Ionization

In the present work we expand the study of time-dependent ionization previously identified to be of pivotal importance for acoustic waves in solar magnetic flux tube simulations. We focus on longitudinal tube waves (LTW) known to be an important heating agent of solar magnetic regions. Our models also consider new results of wave energy generation as well as an updated determination of the mixing length of convection now identified as 1.8 scale heights in the upper solar convective layers. We present 1-D wave simulations for the solar chromosphere by studying tubes of different spreading as function of height aimed at representing tubes in environments of different magnetic filling factors. Multi-level radiative transfer has been applied to correctly represent the total chromospheric emission function. The effects of time-dependent ionization are significant in all models studied. They are most pronounced behind strong shocks and in low density regions, i.e., the middle and high chromosphere. Concerning our models of different tube spreading, we attained pronounced differences between the various types of models, which were largely initiated by different degrees of dilution of the wave energy flux as well as the density structure partially shaped by strong shocks, if existing. Models showing a quasi-steady rise of temperature with height are obtained via monochromatic waves akin to previous acoustic simulations. However, longitudinal flux tube waves are identified as insufficient to heat the solar transition region and corona in agreement with previous studies.Comment: 13 pages, 9 figures, 4 tables; Mon. Not. R. Astron. Soc.; in pres

Locational development profile for Soy and Kocholwo locations, Elgeyo-Marakwet district

ASC – Publicaties niet-programma gebonde

Locational development profile for Soy and Kocholwo locations, Elgeyo-Marakwet district

ASC – Publicaties niet-programma gebonde