Quantifying uncertainty in the biospheric carbon flux for England and Wales

Summary.  A crucial issue in the current global warming debate is the effect of vegetation and soils on carbon dioxide (CO₂) concentrations in the atmosphere. Vegetation can extract CO₂ through photosynthesis, but respiration, decay of soil organic matter and disturbance effects such as fire return it to the atmosphere. The balance of these processes is the net carbon flux. To estimate the biospheric carbon flux for England and Wales, we address the statistical problem of inference for the sum of multiple outputs from a complex deterministic computer code whose input parameters are uncertain. The code is a process model which simulates the carbon dynamics of vegetation and soils, including the amount of carbon that is stored as a result of photosynthesis and the amount that is returned to the atmosphere through respiration. The aggregation of outputs corresponding to multiple sites and types of vegetation in a region gives an estimate of the total carbon flux for that region over a period of time. Expert prior opinions are elicited for marginal uncertainty about the relevant input parameters and for correlations of inputs between sites. A Gaussian process model is used to build emulators of the multiple code outputs and Bayesian uncertainty analysis is then used to propagate uncertainty in the input parameters through to uncertainty on the aggregated output. Numerical results are presented for England and Wales in the year 2000. It is estimated that vegetation and soils in England and Wales constituted a net sink of 7.55 Mt C (1 Mt C = 10¹² g of carbon) in 2000, with standard deviation 0.56 Mt C resulting from the sources of uncertainty that are considered.     

The use of a model in long term planning—A case history

Long term planning in companies can range from the partial simplistic approach to a structured time-consuming ritual. Either extreme can bring planning into disrepute, and both reflect the lack of the proper tools of the trade. Models, by themselves, are no panacea, but properly conceived, constructed, and developed they can transform the planning process. The key to effective and practical models is use, and this can be achieved through direct management involvement on the model's development, and by making sure the model is basically simple and flexible. This article describes how such a model was constructed using a modular approach, and how it was used effectively in long term planning.     

Land-use and environmental pressures resulting from current and future bioenergy crop expansion: A review

Recent energy and climate policies, particularly in the developed world, have increased demand for bioenergy² as an alternative, which has led to both direct and indirect land-use changes and an array of environmental and socio-economic concerns. A comprehensive understanding of the land-use dynamics of bioenergy crop production is essential for the development of sustainable bioenergy and land-use policies. In this paper, we review the patterns and dynamics of land-use change associated with bioenergy crops (hereafter referred to as ’bioenergy-driven land-use change’). The review focuses on four regions as the most prominent locations in which these patterns and changes occur: Brazil; Indonesia and Malaysia; the United States of America (U.S.A.); and the European Union (EU). The review confirms that bioenergy-driven land-use change has affected and will impact most severely on the ’land- and resource-abundant’ developing regions, such as Brazil, where economic development takes priority over sustainable land-use policies, and the enforcement capability is limited. Opportunities for more effective policy are available through the development of international climate change policy (e.g. REDD under the UNFCCC), and certification criteria for sustainable bioenergy products (e.g. EU RED). However, bioenergy produced from no and/or less land-using feedstocks (e.g. wastes and residues), and their associated technologies must be given higher priority to minimise bioenergy-driven land-use change and its negative impacts.     

Evaluating the impact of utility company billing plans on residential energy consumption

Many utility companies offer their customers the choice of participation in an average payment plan, which enables them to pay a fixed sum for their utility bill each month (with final settlement at the end of the billing year), instead of the conventional “pay as you go” billing procedure. Because customers on average payment plans are protected from paying large bills during peak energy-use seasons and because the information about monthly energy use and its cost is perhaps less salient to them, it was hypothesized that customers on the average payment plan would use more electricity than customers not on the plan. Using a nonequivalent control group design, the electricity consumption of a selection of customers of two utility companies (Ns = 475 and 74) was examined. The results showed that there was no evidence to support the hypothesis. Since the logic of hypothesis testing does not permit the ready acceptance of the null hypothesis, several procedural, methodological, and statistical points were made to buttress the conclusion that the average payment plans had no effect on electricity consumption.     

STOCHASTIC KINETIC MODELS: DYNAMIC INDEPENDENCE, MODULARITY AND GRAPHS

The dynamic properties and independence structure of stochastic kinetic models (SKMs) are analyzed. An SKM is a highly multivariate jump process used to model chemical reaction networks, particularly those in biochemical and cellular systems. We identify SKM subprocesses with the corresponding counting processes and propose a directed, cyclic graph (the kinetic independence graph or KIG) that encodes the local independence structure of their conditional intensities. Given a partition [A, D, B] of the vertices, the graphical separation A ⊥ B|D in the undirected KIG has an intuitive chemical interpretation and implies that A is locally independent of B given A ∪ D. It is proved that this separation also results in global independence of the internal histories of A and B conditional on a history of the jumps in D which, under conditions we derive, corresponds to the internal history of D. The results enable mathematical definition of a modularization of an SKM using its implied dynamics. Graphical decomposition methods are developed for the identification and efficient computation of nested modularizations. Application to an SKM of the red blood cell advances understanding of this biochemical system.     

Farmer participation in voluntary land diversion schemes: Some predictions from a survey

National and European agricultural policy schemes are now coming forward which rely on land diversion to achieve a variety of supply control, social and environmental policy goals. Operating on a voluntary basis, these will depend for their success on sufficient numbers of farmers agreeing to enrol land in sufficient quantities and in the right localities. Participation is thus a crucial variable in any assessment of land diversion policies. This paper draws on the results of a farm survey to make some predictions about the level and pattern of uptake of a range of such schemes, identifying the characteristics of resistors and adopters and exploring the motives of participants. It is concluded that land diversion will have most appeal to well-placed farmers who are able to justify the diversion of land out of an agricultural use in terms of forestry and conservation plans which have already been laid. The implication is that voluntary schemes may not be especially powerful instruments for bringing about land use changes on the large number of holdings in the U.K. which presently lack any history of conservation or forestry management, at least not without accompanying reductions in the level of market support for agriculture.     

A Bayesian Time Series Model of Multiple Structural Changes in Level,Trend, and Variance

We investigate whether seasonal-adjustment procedures are, at least approximately, linear data transformations. This question was initially addressed by Young and is important with respect to many issues including estimation of regression models with seasonally adjusted data. We focus on the X-11 program and rely on simulation evidence, involving linear unobserved component autoregressive integrated moving average models. We define a set of properties for the adequacy of a linear approximation to a seasonal-adjustment filter. These properties are examined through statistical tests. Next, we study the effect of X-11 seasonal adjustment on regression statistics assessing the statistical significance of the relationship between economic variables. Several empirical results involving economic data are also reported.     

Attitudes towards globalization and cosmopolitanism: cultural diversity, personal consumption and the national economy

One of the widely accepted consequences of globalization is the development of individual outlooks, behaviours and feelings that transcend local and national boundaries. This has encouraged a re-assessment of important assumptions about the nature of community, personal attachment and belonging in the face of unprecedented opportunities for culture, identities and politics to shape, and be shaped by, global events and processes. Recently, the upsurge of interest in the concept of cosmopolitanism has provided a promising new framework for understanding the nexus between cosmopolitan dispositions and global interconnectedness across cultural, political and economic realms. Using data from a representative social survey of Australians this paper investigates the negotiation of belonging under the conditions of globalization. The data tap into attitudes and behaviours associated with a broad gamut of cosmopolitan traits in the domains of culture, consumption, human rights, citizenship, and international governance. They show how cosmopolitan outlooks are shaped by social structural factors, and how forms of identification with humanity and the globe are fractured by boundaries of self and others, threats and opportunities, and the value of things global and local.