The MAHB, the Culture Gap, and Some Really Inconvenient Truths

Humanity's failure to take adequate actions to stem a likely environmental collapse calls for extraordinary measures to understand and alter human behavior, argues Paul Ehrlich. His Millennium Assessment of Human Behavior (MAHB) aims to chart the path to a sustainable future

Habitat conversion and global avian biodiversity loss

The magnitude of the impacts of human activities on global biodiversity has been documented at several organizational levels. However, although there have been numerous studies of the effects of local-scale changes in land use (e.g. logging) on the abundance of groups of organisms, broader continental or global-scale analyses addressing the same basic issues remain largely wanting. None the less, changing patterns of land use, associated with the appropriation of increasing proportions of net primary productivity by the human population, seem likely not simply to have reduced the diversity of life, but also to have reduced the carrying capacity of the environment in terms of the numbers of other organisms that it can sustain. Here, we estimate the size of the existing global breeding bird population, and then make a first approximation as to how much this has been modified as a consequence of land-use changes wrought by human activities. Summing numbers across different land-use classes gives a best current estimate of a global population of less than 100 billion breeding bird individuals. Applying the same methodology to estimates of original land-use distributions suggests that conservatively this may represent a loss of between a fifth and a quarter of pre-agricultural bird numbers. This loss is shared across a range of temperate and tropical land-use types

Mounding Instability and Incoherent Surface Kinetics

Mounding instability in a conserved growth from vapor is analysed within the framework of adatom kinetics on the growing surface. The analysis shows that depending on the local structure on the surface, kinetics of adatoms may vary, leading to disjoint regions in the sense of a continuum description. This is manifested particularly under the conditions of instability. Mounds grow on these disjoint regions and their lateral growth is governed by the flux of adatoms hopping across the steps in the downward direction. Asymptotically ln(t) dependence is expected in 1+1- dimensions. Simulation results confirm the prediction. Growth in 2+1- dimensions is also discussed.Comment: 4 pages, 4 figure

The process of irreversible nucleation in multilayer growth. II. Exact results in one and two dimensions

We study irreversible dimer nucleation on top of terraces during epitaxial growth in one and two dimensions, for all values of the step-edge barrier. The problem is solved exactly by transforming it into a first passage problem for a random walker in a higher-dimensional space. The spatial distribution of nucleation events is shown to differ markedly from the mean-field estimate except in the limit of very weak step-edge barriers. The nucleation rate is computed exactly, including numerical prefactors.Comment: 22 pages, 10 figures. To appear in Phys. Rev.

Tethered balloon measurements during Arctic spring conditions in Ny-Ålesund in the framework of HALO-(AC)3

The tethered balloon system BELUGA (BalloonbornE moduLar Utility for profilinG the lower Atmosphere) was operated in spring 2022 at the AWIPEV research station (Ny-Ålesund, Svalbard). In-situ profiles of thermodynamic parameters, thermalinfrared radiation, aerosol particle concentrations, and turbulence, were measured and analyzed. Additionally, samples of ice-nucleating particles were collected at various heights. In combination with previous BELUGA datasets, measurements from this campaign provide a solid base for studying the vertical profiles of the radiative energy budget and heating rates in different atmospheric states in the Arctic lower troposphere. Here, example thermal-infrared radiation profiles are presented for a period of persisting cloudless conditions related to a series of marine cold air outbreaks in late March/early April. Measurements in clouds are analyzed for a developing cloud observed on 6 May and display the impact of cloudiness on radiation profiles.Das Fesselballonsystem BELUGA (BalloonbornE moduLar Utility for profilinG the lowerAtmosphere) wurde im Frühjahr 2022 an der Forschungsstation AWIPEVStation (Ny-Ålesund, Svalbard) eingesetzt. In-situ-Profile von thermodynamischen Parametern, terrestrische Strahlung, Aerosolpartikelkonzentrationen und Turbulenz wurden gemessen und ausgewertet. Zusätzlich wurden in verschiedenen Höhen Proben von eiskeimbildenden Partikeln gesammelt. In Kombination mit früheren BELUGA Messungen zu anderen Jahreszeiten und an anderen arktischen Messstandorten bieten die Messungen in Ny-Ålesund eine Grundlage fürweitereUntersuchungen des Strahlungsenergiehaushalts und des Einflusses vonWolken auf atmosphärische Heizraten. Profile der Strahlungsbilanz werden für eine anhaltende Kälteperiode zwischen Ende März bis Anfang April 2022 vorgestellt. Über diesen Zeitraum herrschten vor allem wolkenlose Bedingungen. Weitere Beobachtungen unter einer sich entwickelnden Wolkendecke am 6. Mai 2022 zeigen den Einfluss der Bewölkung auf die Strahlungsprofile

Bunge’s Mathematical Structuralism Is Not a Fiction

In this paper, I explore Bunge’s fictionism in philosophy of mathematics. After an overview of Bunge’s views, in particular his mathematical structuralism, I argue that the comparison between mathematical objects and fictions ultimately fails. I then sketch a different ontology for mathematics, based on Thomasson’s metaphysical work. I conclude that mathematics deserves its own ontology, and that, in the end, much work remains to be done to clarify the various forms of dependence that are involved in mathematical knowledge, in particular its dependence on mental/brain states and material objects

Rigid Singularity Theorem in Globally Hyperbolic Spacetimes

We show the rigid singularity theorem, that is, a globally hyperbolic spacetime satisfying the strong energy condition and containing past trapped sets, either is timelike geodesically incomplete or splits isometrically as space $\times$ time. This result is related to Yau's Lorentzian splitting conjecture.Comment: 3 pages, uses revtex.sty, to appear in Physical Review

Demanding stories: television coverage of sustainability, climate change and material demand

This paper explores the past, present and future role of broadcasting, above all via the medium of television, in shaping how societies talk, think about and act on climate change and sustainability issues. The paper explores these broad themes via a focus on the important but relatively neglected issue of material demand and opportunities for its reduction. It takes the outputs and decision-making of one of the world’s most influential broadcasters, the BBC, as its primary focus. The paper considers these themes in terms of stories, touching on some of the broader societal frames of understanding into which they can be grouped. Media decision-makers and producers from a range of genres frequently return to the centrality of ‘story’ in the development, commissioning and production of an idea. With reference to specific examples of programming, and drawing on interviews with media practitioners, the paper considers the challenges of generating broadcast stories that can inspire engagement in issues around climate change, and specifically material demand. The concluding section proposes actions and approaches that might help to establish material demand reduction as a prominent way of thinking about climate change and environmental issues more widely. This article is part of the themed issue ‘Material demand reduction’

Rate theory for correlated processes: Double-jumps in adatom diffusion

We study the rate of activated motion over multiple barriers, in particular the correlated double-jump of an adatom diffusing on a missing-row reconstructed Platinum (110) surface. We develop a Transition Path Theory, showing that the activation energy is given by the minimum-energy trajectory which succeeds in the double-jump. We explicitly calculate this trajectory within an effective-medium molecular dynamics simulation. A cusp in the acceptance region leads to a sqrt{T} prefactor for the activated rate of double-jumps. Theory and numerical results agree