Five new scenarios, or Shared Socioeconomic Pathways (SSPs), have been developed, spanning a range of challenges to mitigation and challenges to adaptation. The Shared Socioeconomic Pathway 4 (SSP4), "Inequality" or "A Road Divided," is one of these scenarios, characterized by low challenges to mitigation and high challenges to adaptation. We describe, in quantitative terms, the SSP4 as implemented by the Global Change Assessment Model (GCAM), the marker model for this scenario. We use demographic and economic assumptions, in combination with technology and non-climate policy assumptions to develop a quantitative representation of energy, land-use and land-cover, and emissions consistent with the SSP4 narrative. The scenario is one with stark differences within and across regions. High-income regions prosper, continuing to increase their demand for energy and food. Electrification increases in these regions, with the increased generation being met by nuclear and renewables. Low-income regions, however, stagnate due to limited economic growth. Growth in total consumption is dominated by increases in population, not increases in per capita consumption. Due to failures in energy access policies, these regions continue to depend on traditional biofuels, leading to high pollutant emissions. Declining dependence on fossil fuels in all regions means that total radiative forcing absent the inclusion of mitigation or impacts only reaches 6.4 W m -2 in 2100, making this a world with relatively low challenges to mitigation. We explore the effects of mitigation effort on the SSP4 world, finding that the imposition of a carbon price has a varied effect across regions. In particular, the SSP4 mitigation scenarios are characterized by afforestation in the high-income regions and deforestation in the low-income regions. Furthermore, we find that the SSP4 is a world with low challenges to mitigation, but only to a point due to incomplete mitigation of landrelated emissions.

We present a large area photometric survey of the Ursa Minor dwarf spheroidal galaxy and its environs. This survey is intended to trace the distribution of stars outside the nominal tidal radius of this system. Observations were made with the Washington M , Washington T 2 , and DDO51 filters, which in combination have been shown previously to provide reliable stellar luminosity classification for K type stars. We identify giant star candidates with the same distance and metallicity as known Ursa Minor RGB stars extending to approximately 3 • from the center of the dSph. Comparison to catalogues of stars within the tidal radius of Ursa Minor that have been observed spectroscopically suggests that our photometric luminosity classification is 100% accurate. Over a large fraction of the survey area, our photometry is deep enough that blue horizontal branch stars associated with Ursa Minor can also be identified. The spatial distribution of both the candidate Ursa Minor giant stars and the candidate BHB stars are remarkably similar, and, for both samples, a large fraction of the stars are found outside the nominal tidal radius of Ursa Minor. An isodensity contour map of the surface density of stars within the tidal radius of Ursa Minor reveals several morphological peculiarities: (1) The highest density of dSph stars is not found at the center of symmetry of the outer isodensity contours, but instead is offset southwest of center. (2) The overall shape of the outer contours does not appear to be elliptical, but appears S-shaped. A surface density profile was derived for Ursa Minor and compared to those derived from previous studies. We find that previously determined King profiles with ∼ 50 ′ tidal radii do not fit well the distribution of candidate UMi stars identified in this study, which extends to greater radii than these other surveys. A King profile with a much larger tidal radius produces a reasonable fit, however a power law with index −3 provides an even better fit to the densities at radii greater than 20 ′ . The existence of Ursa Minor associated stars at large distances from the core of the galaxy, the peculiar morphology of the galaxy within its tidal radius, and the shape of its surface density profile all suggest that this system is evolving significantly due to the tidal influence of the Milky Way. However, the photometric data on Ursa Minor stars alone do not allow us to determine if the candidate extratidal stars are now unbound or if they remain bound to the dSph within an extended dark matter halo.

Abstract. This paper describes GCAM v5.1, an open source model that represents the linkages between energy, water, land, climate, and economic systems. GCAM is a market equilibrium model, is global in scope, and operates from 1990 to 2100 in 5-year time steps. It can be used to examine, for example, how changes in population, income, or technology cost might alter crop production, energy demand, or water withdrawals, or how changes in one region's demand for energy affect energy, water, and land in other regions. This paper describes the model, including its assumptions, inputs, and outputs. We then use 11 scenarios, varying the socioeconomic and climate policy assumptions, to illustrate the results from the model. The resulting scenarios demonstrate a wide range of potential future energy, water, and land uses. We compare the results from GCAM v5.1 to historical data and to future scenario simulations from earlier versions of GCAM and from other models. Finally, we provide information on how to obtain the model.