Imprecise probabilities of climate change: aggregation of fuzzy scenarios and model uncertainties

Whilst the majority of the climate research community is now set upon the objective of generating probabilistic predictions of climate change, disconcerting reservations persist. Attempts to construct probability distributions over socio-economic scenarios are doggedly resisted. Variation between published probability distributions of climate sensitivity attests to incomplete knowledge of the prior distributions of critical parameters and structural uncertainties in climate models. In this paper we address these concerns by adopting an imprecise probability approach. We think of socio-economic scenarios as fuzzy linguistic constructs. Any precise emissions trajectory (which is required for climate modelling) can be thought of as having a degree of membership in a fuzzy scenario. Next, it is demonstrated how fuzzy scenarios can be propagated through a low-dimensional climate model, MAGICC. Fuzzy scenario uncertainties and imprecise probabilistic representation of climate model uncertainties are combined using random set theory to generate lower and upper cumulative probability distributions for Global Mean Temperature anomaly. Finally we illustrate how non-additive measures provide a flexible framework for aggregation of scenarios, which can represent some of the semantics of socio-economic scenarios that defy conventional probabilistic representation.     

Precipitation interception in Australian tropical rainforests: II. Altitudinal gradients of cloud interception,stemflow, throughfall and interception

This article presents a comprehensive study of canopy interception in six rainforests in Australia's Wet Tropics for periods ranging between 2 and 3·5 years. Measurements of rainfall, throughfall, stemflow and cloud interception were made at sites characterized by different forest types, canopy structure, altitude, rainfall and exposure to prevailing winds. Throughfall at these sites ranged between 64 and 83% of total precipitation inputs, while stemflow ranged between 2 and 11%. At sites higher than 1000 m, cloud interception was found to contribute up to 66% of the monthly water input to the forest, more than twice the rainfall at these times. Over the entire study period, cloud interception accounted for between 4 and 30% of total precipitation inputs, and was related more to the exposure of sites to prevailing winds than to altitudinal differences alone. Over the duration of the study period, interception losses ranged between 22 and 29% of total water input (rainfall and cloud interception) at all sites except the highest altitude site on Bellenden Ker, where interception was 6% of total water input. This smaller interception loss was the result of extremely high rainfall, prolonged immersion in cloud and a sparser canopy. On a monthly basis, interception losses from the six sites varied between 10 and 88% of rainfall. All sites had much higher interception losses during the dry season than in the wet season because of the differences in storm size and rainfall intensity. The link between rainfall conditions and interception losses has important implications for how evaporative losses from forests may respond to altered rainfall regimes under climate change and/or large‐scale atmospheric circulation variations such as El Niño. Copyright © 2007 John Wiley & Sons, Ltd.     

Measurements of transpiration in four tropical rainforest types of north Queensland,Australia

Transpiration of four different rainforest types in north Queensland, Australia, was determined using the heat pulse technique for periods ranging between 391 and 657 days. Despite the complexity of the natural rainforest systems being studied, the relationship between sample tree size and daily water use was found to be strong, thus providing a robust means by which to scale transpiration from individual trees to the entire forest stand. Transpiration was shown to be dependent on solar radiation and atmospheric demand for moisture with little evidence of limitation by soil moisture supply. Total stand transpiration was controlled by forest characteristics such as stem density, size distribution and sapwood area. Annual transpiration for each of the four sites ranged between 353 mm for cloud forest and 591 mm for montane rainforest. In comparison with the international literature, transpiration from Australian rainforests is low; the reasons for this could be related to a combination of differences in forest structure, climatic conditions, canopy wetness duration and tree physiology. Copyright © 2007 John Wiley & Sons, Ltd.     

Avoiding the Ghetto through hope and fear: an analysis of immanent technology using ideal types

With over one hundred million smart-phone users in the world, mobile, spatially-aware devices are radically altering how individuals move through and experience both physical and social environments. This article presents a theoretical and methodological framework for engaging the emerging geoweb as part of a longer tradition of research into society and technology. A close reading of Microsoft’s Pedestrian Route Production patent, dubbed the “avoid ghetto GPS”, is used to construct two ideal type futures—one hopeful and one frightening. One where spatial technology ensures efficiency, safety, and new forms of coordination, while the other algorithmically sorts society by race and class. Despite not yet and potentially never existing, the patent offers a viable means through which potential futures are made real in the present. Through comparative analysis of these futures, their underlying commonalities are drawn out, revealing the relationship between technology and the delimitation of human experience. This analysis avoids grand narratives and teleological arguments, while making it possible to draw forth the unthought acceptance within each ideal type for the future: the continuing shift of human life itself towards a teleological, always already-calculated standing-reserve. The work on technology of Martin Heidegger and Herbert Marcuse (re)situate the geoweb within long-standing theoretical work on technology and its role in society, modernity, and capitalism.     

On the estimation of long-wave radiation flux from clear skies

Summary Data from measurements of long-wave radiation at Barcelona were used to test the validity of several methods for computing this component of the radiation balance in clear sky conditions.Two types of formulae, the analytically derived formulae of Swinbank and Brutsaert 1 and 2 and the empirically obtained formulae of Brunt, Idso and Jackson and Idso 1 and 2 were used in the test.Most of these methods are derived for a particular location and utilize local empirical coefficients. However, there are several which have been considered more universal.Estimates by the two methods give approximately the same value when the screen level air temperature is above 0°C.In addition, the test for temperatures below 0°C shows several discrepancies between the observed and estimated values of long-wave atmospheric radiation. This fact suggests that modifications may be needed for both analytical and empirical formulae. However, since we have few measurements in the temperature regime below 0°C, this statement cannot be justified as a conclusion of this study.

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Zusammenfassung Es werden Daten der langwelligen atmosphärischen Strahlung bei Barcelona herangezogen, um verschiedene Methoden zur Bestimmung dieser Komponente der Strahlungsbilanz bei klarem Himmel zu vergleichen. Dazu werden zwei unterschiedliche Formeltypen, die analytischen nach Swinbank und Brutsaert (1 und 2) und empirische nach Brunt, Idso und Jackson sowie Idso (1 und 2) benützt.Von diesen Methoden wurden die meisten für einen bestimmten Ort entwickelt und verwenden daher lokale empirische Koeffizienten. Allerdings gibt es einige, die als allgemein verwendbar angesehen werden.Für beide Typen der Abschätzung ergeben sich für Lufttemperaturen über 0°C im Hüttenniveau ähnliche Werte. Bei Lufttemperaturen unter 0°C zeigen sich jedoch einige Unterschiede zwischen den beobachteten und geschätzten Werten der langwelligen atmosphärischen Strahlung. Das legt nahe, die Koeffizienten sowohl für die analytischen als auch die empirischen Formeln anzupassen. Leider war das auf Grund des geringen Datenmaterials bei Temperaturen unter 0°C innerhalb dieser Untersuchung nicht möglich.

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With 2 Figures     

Probabilistic spatial risk assessment of heat impacts and adaptations for London

High temperatures and heatwaves can cause large societal impacts by increasing health risks, mortality rates, and personal discomfort. These impacts are exacerbated in cities because of the Urban Heat Island (UHI) effect, and the high and increasing concentrations of people, assets and economic activities. Risks from high temperatures are now widely recognised but motivation and implementation of proportionate policy responses is inhibited by inadequate quantification of the benefits of adaptation options, and associated uncertainties. This study utilises high spatial resolution probabilistic projections of urban temperatures along with projections of demographic change, to provide a probabilistic risk assessment of heat impacts on urban society. The study focuses on Greater London and the surrounding region, assessing mortality risk, thermal discomfort in residential buildings, and adaptation options within an integrated framework. Climate change is projected to increase future heat-related mortality and residential discomfort. However, adjusting the temperature response function by 1–2 °C, to simulate adaptation and acclimatisation, reduced annual heat related mortality by 32–69 % across the scenarios tested, relative to a no adaptation scenario. Similar benefits of adaptation were seen for residential discomfort. The study also highlights additional benefits in terms of reduced mortality and residential discomfort that mitigating the urban heat island, by reducing albedo and anthropogenic heat emissions, could have.     

The impact of pro‐glacial lakes on downstream sediment delivery in Norway

Glacier recessions caused by climate change may uncover pro‐glacial lakes that form important sedimentation basins regulating the downstream sediment delivery. The impact of modern pro‐glacial lakes on fluvial sediment transport from three different Norwegian glaciers: Nigardsbreen, Engabreen and Tunsbergdalsbreen, and their long‐term development has been studied. All of these lakes developed in modern times in overdeepened bedrock basins. The recession of Nigardsbreen uncovered a 1.8 km long and on average 15 m deep pro‐glacial lake basin during 1937 to 1968. Since then the glacier front has been situated entirely on land, and the sediment input and output of the lake has been measured. The suspended sediment transport into and out of the lake averaged 11 730 t yr^?1 and 2340 t yr^?1 respectively. Thus, 20% remained in suspension at the outlet. The measured mean annual bedload supplied to the lake was 11 800 t yr^?1, giving a total transport of 23 530 t yr^?1 which corresponds to a specific sediment yield of 561 t km^?2 yr^?1. A 1.9 km long and up to 90 m deep pro‐glacial lake basin downstream from Engabreen glacier was uncovered during 1890 to 1944. The average suspended sediment load delivered from the glacier during the years 1970–1981 amounted to 12 375 t yr^?1and the transport out of the lake was 2021 t yr^?1, giving an average of 16% remaining in suspension. The mean annual bedload was 8000 t yr^?1, thus the total transport was 20 375 t yr^?1, giving a specific sediment yield of 566 t km^?2 yr^?1. For Tunsbergdalsbreen glacier, measurements in the early 1970s indicated that the suspended sediment transport was on average 44 000 t yr^?1. From 1987 to 1993 the recession of the glacier uncovered a small pro‐glacial lake, 0.3 km long and around 9 m deep. Downstream from this, the suspended sediment load measured in 2009 was 28 000 t yr^?1, indicating that as much as 64% remained in suspension. Flow velocity, grain size of sediment, and morphology of the lake are important factors controlling the sedimentation rate in the pro‐glacial lakes. A survey of the sub‐glacial morphology of Tunsbergdalsbreen revealed that there are several overdeepened basins beneath the glacier. The largest is 4 km long and 100 m deep. When the glacier melts back they will become lakes and act as sedimentation basins. Despite an expected increase in sediment yield from the glacier, little sediment will pass these lakes and downstream sediment delivery will be reduced markedly. Beneath Nigardsbreen there was only a small depression that may form a lake and the sediment delivery will not be significantly affected. © 2014 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.