515 research outputs found
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A probabilistic assessment of sea level variations within the Last Interglacial stage
No full textThe Last Interglacial (LIG) stage (ca. 130–115 ka) provides a relatively recent example of a world with both poles characterized by greater-than- Holocene temperatures similar to those expected later in this century under a range of greenhouse gas emission scenarios. Previous analyses inferred that LIG mean global sea level (GSL) peaked 6–9 m higher than today (Kopp et al. 2009; Dutton & Lambeck 2012). Here, we extend our earlier work to perform a probabilistic assessment of sea level variability within the LIG highstand. Using the terminology for probability employed in the Intergovernmental Panel on Climate Change (IPCC) assessment reports, we find it extremely likely (95% probability) that the paleo-sea level record allows resolution of at least two intra-LIG sea level peaks and likely (67% probability) that the magnitude of low-to-high swings exceeded 4 m. Moreover, it is likely that there was a period during the LIG in which GSL rose at a 1000-year average rate exceeding 3 m/ky, but unlikely (33% probability) that the rate exceeded 7 m/ky and extremely unlikely (5% probability) that it exceeded 11 m/ky. These rate estimates can provide insight into rates of Greenland and/or Antarctic melt under climate conditions partially analogous to those expected in the twenty- first century.This is the authors’ preprint version of the manuscript: 23 January 2013. Originally submitted 18 September 2012. Accepted for publication in Geophysical Journal International, published by Oxford University Press.Peer reviewe
How does fair trade, as practised by Trade Aid and MINKA, contribute to the aspirations of Quechua producers in Peru?
No full textAs part of a Master of Indigenous Studies from the University of Otago, Trade Aid staff member, Michelia Ward, conducted research throughout 2011 and 2012 on whether fair trade is able to contribute to the aspirations of indigenous producers. The research focused on fair trade as practiced by Trade Aid, New Zealand and one of its Peruvian partners, MINKA.Fair trade is a development mechanism that aims to support food and craft producers around the world to improve their lives through trade. Many indigenous communities are producers of craft or food products such as woven textiles and coffee, and have engaged in fair trade relationships selling mainly to Western consumers. Fair trade organisations have universal principles that provide guarantees to consumers about working conditions, fair payment and trading relations with producer groups. This research project focuses on whether a universal framework designed to bring development to disadvantaged and marginalized producers can work for unique indigenous cultures across multiple continents. This research focuses on Trade Aid in New Zealand and their partnership with a Peruvian fair trade organisation, MINKA, who works with Quechua producers in the Andes. Indigenous theorists place large value on local epistemes (knowledge systems) and local solutions to local problems. Is fair trade one of these local solutions, or just another solution imposed from the outside upon indigenous producers
Geographic Variability of Sea-Level Change
No full textLocal sea-level changes differ significantly from global-mean sea-level change as a result of (1) non-climatic, geological background processes; (2) atmosphere/ocean dy- namics; and (3) the gravitational, elastic, and rotational “fin- gerprint” effects of ice and ocean mass redistribution. Though the research communities working on these different effects each have a long history, the integration of all these different processes into interpretations of past changes and projections of future change is an active area of research. Fully character- izing the past contributions of these processes requires information from sources covering a range of timescales, including geological proxies, tide-gauge observations from the last ~3 centuries, and satellite-altimetry data from the last ~2 decades. Local sea-level rise projections must account for the different spatial patterns of different processes, as well as potential correlations between different drivers.Peer reviewe
Temperature-driven global sea-level variability in the Common Era
No full textWe assess the relationship between temperature and global sea-level (GSL) variability over the Common Era through a statistical metaanalysis of proxy relative sea-level reconstructions and tide-gauge data. GSL rose at 0.1 ± 0.1 mm/y (2σ) over 0–700 CE. A GSL fall of 0.2 ± 0.2 mm/y over 1000–1400 CE is associated with ∼0.2 °C global mean cooling. A significant GSL acceleration began in the 19th century and yielded a 20th century rise that is extremely likely (probability P≥0.95) faster than during any of the previous 27 centuries. A semiempirical model calibrated against the GSL reconstruction indicates that, in the absence of anthropogenic climate change, it is extremely likely (P=0.95) that 20th century GSL would have risen by less than 51% of the observed 13.8±1.5 cm. The new semiempirical model largely reconciles previous differences between semiempirical 21st century GSL projections and the process model-based projections summarized in the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.This article is available Open Access at the Link to published version: http://dx.doi.org/10.1016/j.emospa.2016.02.006Also available as related resources: Supporting Information (PDF), Dataset S1 (PDF), Dataset S2 (Excel), Dataset S3 (Excel).Peer reviewe
Tobias Smollett novelist
No full textTobias Smollett (1721-1771) was a man of letters in the fullest sense. He was not only a novelist but also a playwright, poet, journalist, historian, travel writer, critic, translator, and editor. Trained as a physician, he saw the world with acutely sensitive eyes, believing that what was externally visible signified and gave definition to what could be known about the private, interior life. His fiction is therefore distinguished by its intensely visual qualities. Tobias Smollett: Novelist goes beyond all previous critical studies in its attention to these qualities in Smollett's novels, reading them as exercises of a visual imagination. Jerry C. Beasley's book is both focused and broad in its range, crossing disciplines and genres as it seeks to demonstrate intersections between the graphic and verbal arts, always with an eye to how Smollett crafted his stories. Seventeen illustrations, many of them from works by Hogarth, complement the text. This book honors Smollett as an author who wrote in an unorthodox but compelling way and makes the complexities of his narratives more accessible than they have ever been before
Essays in econometrics and random matrix theory
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Economics, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references.This dissertation develops new econometric procedures for the analysis of high-dimensional datasets commonly encountered in finance, macroeconomics or industrial organization. First, I show that traditional approaches to the estimation of latent factors in financial data underestimate the number of risk factors. They are also biased towards a single market factor, the importance of which is overestimated in samples. In Chapter 3, I derive a new consistent procedure for the estimation of the number of latent factors by examining the effect of the idiosyncratic noise in a factor model. Furthermore, I show that the estimation of factor loadings by Principal Components Analysis is inconsistent for weak factors and suggest alternative Instrumental Variables procedures. Chapter 4 uses the theoretical results of the earlier chapters to estimate the stochastic dimension of the US economy and shows that global risk factors may obfuscate the relationship between inflation and unemployment. Chapter 5 (co-authored with Jerry Hausman) suggests a new procedure for the estimation of discrete choice models with random coe±cients and shows that ignoring individual taste heterogeneity can lead to misleading policy counterfactuals.by Matthew C. Harding.Ph.D
Probabilistic assessment of sea level during the last interglacial stage
No full textWith polar temperatures ∼3–5 °C warmer than today, the last interglacial stage (∼125 kyr ago) serves as a partial analogue for 1–2 °C global warming scenarios. Geological records from several sites indicate that local sea levels during the last interglacial were higher than today, but because local sea levels differ from global sea level, accurately reconstructing past global sea level requires an integrated analysis of globally distributed data sets. Here we present an extensive compilation of local sea level indicators and a statistical approach for estimating global sea level, local sea levels, ice sheet volumes and their associated uncertainties. We find a 95% probability that global sea level peaked at least 6.6 m higher than today during the last interglacial; it is likely (67% probability) to have exceeded 8.0 m but is unlikely (33% probability) to have exceeded 9.4 m. When global sea level was close to its current level (≥-10 m), the millennial average rate of global sea level rise is very likely to have exceeded 5.6 m kyr-1 but is unlikely to have exceeded 9.2 m kyr-1. Our analysis extends previous last interglacial sea level studies by integrating literature observations within a probabilistic framework that accounts for the physics of sea level change. The results highlight the long-term vulnerability of ice sheets to even relatively low levels of sustained global warming.This is a post-print version of an article published in Nature. The published version is available at http://www.nature.com/nature/journal/v462/n7275/full/nature08686.htmlPeer reviewe
Reconciling Past Changes in Earth Rotation with 20th Century Global Sea-Level Rise: Resolving Munk’s Enigma
No full textIn 2002, W. H. Munk defined an important enigma of 20th century global mean sea-level (GMSL) rise that has yet to be resolved. First, he listed three canonical observations related to Earth rotation – (1) the slowing of the Earth’s rotation rate over the last three millennia inferred from ancient eclipse observations, and changes in (2) the amplitude and (3) orientation of the Earth’s rotation vector over the last century estimated from geodetic and astronomic measurements – and argued that they could all be fit by a model of ongoing glacial isostatic adjustment (GIA) associated with the last ice age. Second, he demonstrated that prevailing estimates of the 20th century rate of GMSL rise (~1.5-2.0 mm/yr), after correction for the maximum signal from ocean thermal expansion, implied mass flux from ice sheets and glaciers at a level that would grossly misfit the residual, GIA-corrected observations of Earth rotation. We demonstrate that the combination of lower estimates of 20th century GMSL rise (up to 1990), improved modeling of the GIA process, and a correction of eclipse records for a signal due to angular momentum exchange between the fluid outer core and mantle reconciles all three Earth rotation observations. This resolution adds confidence to recent estimates of the individual contributions to 20th century sea-level change and to projections of GMSL rise to the end of the 21st century based upon them.Peer reviewe
Earth Rotation Changes Since -500 CE Driven by Ice Mass Variations
No full textWe predict the perturbation to the Earth’s length-of-day (LOD) over the Common Era using a recently derived estimate of global sea-level change for this time period. We use this estimate to derive a time series of “clock error”, defined as the difference in timing of two clocks, one based on a theoretically invariant time scale (terrestrial time) and one fixed to Earth rotation (universal time), and compare this time series to millennial scale variability in clock error inferred from ancient eclipse records. Under the assumption that global sea-level change over the Common Era is driven by ice mass flux alone, we find that this flux can reconcile a significant fraction of the discrepancies between clock error computed assuming constant slowing of Earth's rotation and that inferred from eclipse records since 700 CE. In contrast, ice mass flux cannot reconcile the temporal variability prior to 700 CE.Peer reviewe
Review of literature on the career transitions of performing artists pursuing career development
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