[Show abstract][Hide abstract] ABSTRACT: Het PBL-normenkader voor modellen maakt inzichtelijk of noodzakelijke procedures rond de ontwikkeling, het beheer en het gebruik van modellen correct doorlopen worden en is dus een praktisch regelgevend instrument voor kwaliteitszorg rond modellen. Aan de hand van de in het normenkader vastgestelde normen beoordeelt het PBL modellen op een uniforme manier. Het normenkader bestaat uit een serie vragen (normen) met toelichtingen en aandachtspunten. De antwoorden moeten altijd gemotiveerd worden. Bij de motivatie moet aangegeven worden in welke mate aan de aandachtspunten voldaan is.
[Show abstract][Hide abstract] ABSTRACT: In a recent approach, Baader and Distel proposed an algorithm to axiomatize all terminological knowledge that is valid in a given data set and is expressible in the description logic ELK. This approach is based on the mathematical theory of formal concept ...
[Show abstract][Hide abstract] ABSTRACT: Environmental computer models are considered essential tools in supporting environmental decision making, but their main value is that they allow a better understanding of our complex environment. Despite numerous attempts to promote good modelling practice, transparency of current environmental computer models is limited, which hinders progress in both science and policy making. An important cause is that the structure, meaning and context of environmental computer models is often not clear for other people than the model developers. In the proposed research project we would like to find out whether it is possible to increase the transparency of environmental computer models by making their underlying conceptual model explicit. In preliminary research we identified the following challenges: 1) many model developers are mainly focused on the computational instead of the descriptive aspects of computer models 2) many environmental modellers may not consider the lack of transparency a big problem nor do they see computer scientists as natural partners in cooperation. However, we think that both environmental and computer science could benefit from an interdisciplinary or even a totally integrated approach. We expect that experimenting with tools and methods from computer science could teach us important lessons on the practice of environmental modelling and hopefully guide us to this novel, integrated way of performing e-science.
[Show abstract][Hide abstract] ABSTRACT: Aim This paper presents a tool for long-term global change studies; it is an update of the History Database of the Global Environment (HYDE) with estimates of some of the underlying demographic and agricultural driving factors.
Methods Historical population, cropland and pasture statistics are combined with satellite information and specific allocation algorithms (which change over time) to create spatially explicit maps, which are fully consistent on a 5′ longitude/latitude grid resolution, and cover the period 10,000 bc to ad 2000.
Results Cropland occupied roughly less than 1% of the global ice-free land area for a long time until ad 1000, similar to the area used for pasture. In the centuries that followed, the share of global cropland increased to 2% in ad 1700 (c. 3 million km2) and 11% in ad 2000 (15 million km2), while the share of pasture area grew from 2% in ad 1700 to 24% in ad 2000 (34 million km2) These profound land-use changes have had, and will continue to have, quite considerable consequences for global biogeochemical cycles, and subsequently global climate change.
Main conclusions Some researchers suggest that humans have shifted from living in the Holocene (emergence of agriculture) into the Anthropocene (humans capable of changing the Earth's atmosphere) since the start of the Industrial Revolution. But in the light of the sheer size and magnitude of some historical land-use changes (e.g. as result of the depopulation of Europe due to the Black Death in the 14th century and the aftermath of the colonization of the Americas in the 16th century) we believe that this point might have occurred earlier in time. While there are still many uncertainties and gaps in our knowledge about the importance of land use (change) in the global biogeochemical cycle, we hope that this database can help global (climate) change modellers to close parts of this gap.
[Show abstract][Hide abstract] ABSTRACT: The environmentally persistent perfluorooctane sulfonate (PFOS) is a perfluoroalkylated acid (PFA), which has been found to accumulate and biomagnify through food webs all over the world. In the present investigation, the accumulation kinetics of PFOS was explored using the bioaccumulation model OMEGA. As accumulation behavior of PFOS may show similarities to fatty acids as well as to neutral organic compounds, different modeling approaches were used. Accumulation kinetics of PFOS was modeled similar to (1) moderately and (2) highly hydrophobic compounds, (3) metals and (4) as a combination of hydrophobic compounds and metals. Modeled elimination and uptake rate constants were compared to empirical rate constants from literature. Subsequently, model predictions were compared to field-based biota-suspended solids accumulation ratios (BSAF) in the estuarine food chain of the Western Scheldt, The Netherlands. Results show that uptake of PFOS is comparable to moderately hydrophobic compounds and elimination is best described by elimination kinetics of metals. These observations indicate that the accumulation behavior of PFOS is comparable to that of short and medium chained fatty acids.
[Show abstract][Hide abstract] ABSTRACT: Integrated assessment models are used to analyze global change issues and they allow a better understanding of our complex environment. It is crucial to be able to relate these models to their scientific basis, both for interpretation and validation purposes. Current model evaluation procedures focus on model behavior analysis; the conceptual knowledge and assumptions embedded in integrated assessment models are hardly tested. As such, current model evaluation procedures do not contribute to the understanding of the structure of the models and the selected mechanisms and assumptions. We submit that evaluation of the scientific basis of integrated assessment models should follow the standard procedures for evaluation of scientific theories, which implies that these models should be subjected to critical peer reviews. However, much knowledge is hidden in the source code and therefore not accessible to peers. In this paper we propose to use ontologies – explicit specifications of shared conceptual knowledge – to represent the knowledge encoded in integrated assessment models in a clear and transparent way. We show the proposed peer review evaluation procedure in a case study concerning a system-dynamics model on residential energy use in India. We found that the ontology helped peers to obtain more information on the model and to gain more insight in its structure. However, a better balance between different types of model documentation and explicit links between them are needed to improve the understanding by the peers. We believe that ontologies can be exploited further in a computational sense in order to achieve model transparency.
[Show abstract][Hide abstract] ABSTRACT: Spreadsheets are frequently used by scientists to store and analyze research data. To enable integration and reusability of scientific spreadsheet data it is important to explicate the underlying concepts and relations. In this paper we explore to which extent the conceptual model of a research project can be recognized in its spreadsheet implementation. We perform a manual analysis of spreadsheets of existing research from the domain of environmental science. We formally describe the semantics of the spreadsheets in an ontology and record our approach in heuristics. We interview the original developers of the spreadsheets to compare our findings with their views. Our reconstructed conceptual model does not conflict with the developer's views, but represents a different perspective, as the developers are primarily focussed on the calculation workflow.