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This chapter shows that all the regions considered can be classified as ‘marginal’. The marginality in most regions depicts some degree of sensitivity which can augment the endangerment of the regional ecosystem by any agricultural or gathering activity. There is a great regional variation in precipitation changes, both in sign and magnitude. In order to perform a pattern analysis of globally relevant interactions between nature and humankind, it is not possible to rely on a single best strategy, possibly based on a large set of data. ‘Generalized’ means that regionally specific processes and phenomena can be mapped onto one single symptom. Most prominent is the diffusion of greenhouse gases, in particular carbon dioxide, inducing a systemic global change of the atmosphere’s energy balance. Global Change is more than the pure addition or parallel occurrence of symptoms. It is the complex and sometimes highly inertial interaction between the symptoms which constitute the risks people are facing and have to handle.

An approach to considering changes in flooding probability in the integrated assessment of climate change is introduced. A reduced-form hydrological model for flood prediction and a downscaling approach suitable for integrated assessment modeling are presented. Based on these components, the fraction of world population living in river basins affected by changes in flooding probability in the course of climate change is determined. This is then used as a climate impact response function in order to derive emission corridors limiting the population affected. This approach illustrates the consideration of probabilistic impacts within the framework of the tolerable windows approach. Based on the change in global mean temperature, as calculated by the simple climate models used in integrated assessment, spatially resolved changes in climatic variables are determined using pattern scaling, while natural variability in these variables is considered using twentieth century deviations from the climatology. Driven by the spatially resolved climate change, the hydrological model then aggregates these changes to river basin scale. The hydrological model is subjected to a sensitivity analysis with regard to the water balance, and the uncertainty arising through the different projections of changes in mean climate by differing climate models is considered by presenting results based on different models. The results suggest that up to 20% of world population live in river basins that might inevitably be affected by increased flood events in the course of global warming, depending on the climate model used to estimate the regional distribution of changes in climate.

A qualitative model of smallholder agriculture with a few core variables and two allocation rules for labour and investment in agricultural resources was developed to cover spatial heterogeneity in Northeast Brazil. This region is characterised by large natural and socio-economic variance, recurrent droughts and widespread rural poverty. The resulting system dynamics essentially consists of a cycle of four qualitative states, each depicting a typical pattern of trends in smallholder agriculture. Municipal statistical data were used to identify the spatial distribution of these patterns for the 1990s and the internal transition likelihood between subsequent states. Additionally the influence of external perturbations like droughts and producer price shocks on the smallholder system was investigated.

A simple two-box model of the hemispheric thermohaline circulation (THC) is considered. The model parameterizes fluctuations in the freshwater forcing by a stochastic process. The dependence of the power spectral density and the lifetime of quasistationary states of the THC on the distance to the bifurcation point, where the THC collapses, is calculated analytically. It is shown that power spectral properties change as the system is moved closer to the bifurcation point. These changes allow an estimate of the distance to the bifurcation point.

The tolerable windows approach (TWA) allows the climate policyformulation process to be safeguarded in the following way. First,guardrails are defined in order to exclude intolerable climatechange impacts, on the one hand, and unacceptable socioeconomicconsequences of climate change mitigation measures, on the other.Second, a scientific analysis is conducted to investigate thefeatures of those emission paths that are compatible with theguardrail constraints. The fundamental methodology of the TWA isbest described in terms of the theory of differentialinclusions. This emerging mathematical theory already providesnumerical methods applicable as long as the underlying integratedassessment models are of limited complexity. In order to identifyemissions corridors, we propose a novel calculation schemeapplicable also for large-scale integrated assessment models.

An integrated assessment model (IAM) conceived in the vein ofthe inverse approach is introduced. The model is designed tohelp social actors in making informed judgments about climatechange impact targets, mitigation costs, and implementation mechanisms.Based on these normative decisions, the model verifies whetherthere exist long-term future emission paths that satisfy theuser-defined constraints. If they do, the model determines anemission corridor containing all permissible emission trajectories.An overview of the IAM is provided and short descriptions ofthe model components are presented. Forward and inverse modesof application are explained. Examples based on impacts of climatechange on aggregated potential crop production in Western Europeand South Asia illustrate how the model can be applied in differentmodes. The examples demonstrate how the inverse approach separatessocial judgments shaping climate policy from the model-basedanalysis of their implications. The examples also show the differencein climate change tolerance between developed regions in temperatezones and less developed regions in already warm climate zones.

A dynamic description of Global Change on an intermediate functional scale on the basis of approximately independent sub-models is elaborated. Sixteen of these sub-models are primarily identified as Hazardous Functional Patterns (HFPs) generating nonsustainable trajectories (Syndromes) of the civilisation/nature system. After an ‘‘idealistic deduction’’ of the main concepts an iterative procedure – formally based on Qualitative Differential Equations – is introduced which allows the systematic generalisation of case study based knowledge to obtain consistent HFPs on a coarser functional scale. The method is illustrated with the Sahel HFP.

(2002). Exploring Options for Global Climate Policy. A New Analytical Framework. Environment: Science and Policy for Sustainable Development: Vol. 44, No. 5, pp. 22-34.

We present a novel methodology to integrate qualitative knowledge from different case studies on Global Change related issues into a single framework. The method is based on the concept of qualitative differential equations (QDEs) which represents a mathematically well-defined approach to investigate classes of ordinary differential equations (ODEs) used in conventional modeling exercises. These classes are defined by common qualitative features, e.g., monotonicity, signs, etc. Using the QSIM-algorithm it is possible to derive the set of possible solutions of all ODEs in the class. By this one can formulate a common, qualitatively specified cause–effect scheme valid for all case studies. The scheme is validated by testing it against the actually observed histories in the study regions with respect to their reconstruction by the corresponding QDE. The method is outlined theoretically and exemplary applied to the problem of land-use changes due to smallholder agriculture in developing countries. It is shown that the seven case-studies used can be described by a single cause–effect scheme which thus constitutes a pattern of Global Change. As a generally valid prerequisite for sustainability of this kind of land-use the presence of wage labor is shown to represent a decisive factor.

A novel transdisciplinary approach to investigate Global Change (GC) is presented. The approach rests on the decomposition of the intrigue dynamics of GC into patterns of civilization–nature interactions (“syndromes”) by an iterative scientific process of observations, data and system theoretical analyses, and modelling attempts. We illustrate the approach by a detailed analysis of the Sahel Syndrome, which describes the rural poverty driven overuse of natural resources. The investigation is performed by (i) identifying relevant “symptoms” and interlinkages which are characteristics for this pattern, and (ii) a qualitative model representing the internal dynamics of the essential flywheel. The geographical patchwork of the regions affected by the syndrome which is obtained by global data analysis, proves the high global relevance of this pattern. The qualitative model is employed for an evaluation of basic policy strategies debated in the context of rural poverty driven environmental degradation. It turns out that a mixed policy of combating poverty and introducing soil preserving agricultural techniques and practices is most promising to tackle the syndrome dynamics.

The tolerable windows (TW) approach is presented as a novel scheme for integrated assessment of climate change. The TW approach is based on the specification of a set of guardrails for climate evolution which refer to various climate-related attributes. These constraints, which define what we call tolerable windows, can be purely systemic in nature – like critical thresholds for the North Atlantic Deep Water formation – or of a normative type – like minimum standards for per-capita food production worldwide. Starting from this catalogue of knock-out criteria and using appropriate modeling techniques, those policy strategies which are compatible with all the constraints specified are sought to be identified. In addition to the discussion of the basic elements and the general theory of the TW approach, a modeling exercise is carried out, based on simple models and assumptions adopted from the German Advisory Council on Global Change (WBGU). The analysis shows that if the global mean temperature is restricted to 2°C beyond the preindustrial level, the cumulative emissions of CO2 are asymptotically limited to about 1550 Gt C. Yet the temporal distribution of these emissions is also determined by the climate and socio-economic constraints: using, for example, a maximal tolerable rate of temperature change of 0.2°C/dec and a smoothly varying emissions profile, we obtain the maximal cumulative emissions, amounting to 370 Gt C in 2050 and 585 Gt C in 2100.

Starting from the basic assumption of the syndrome concept that essentially all of the present problematic civilization–nature interactions on the global scale can be subdivided into a limited number of typical patterns, the analysis of the response of these patterns (syndromes) to climate change can make a major contribution to climate impact research, surmounting the difficulties of more common sectoral “ceteris paribus” impact studies with respect to their systemic integration. In this paper we investigate in particular the influence of climate on the regional proneness or “disposition” towards one of the most important syndromes with respect to famines and malnutrition, the “Sahel Syndrome”. It describes the closely interlinked natural and socioeconomic aspects of rural poverty driven degradation of soil and vegetation on marginal sites. Two strategies of global climate impact assessment on a spatial 0.5°×0.5° grid were pursued: (a) As a measure for the climate sensitivity of the regional proneness, the absolute value of the gradient of the disposition with respect to the global field of 3} 12 monthy normals of temperature, irradiation and precipitation is calculated. (b) The disposition was evaluated for two different climate forecasts under doubled atmospheric CO2 concentration. For both strategies two new quantitative global models were incorporated in a fuzzy-logic-based algorithm for determining the disposition towards the Sahel Syndrome: a neural-net-based model for plant productivity and a waterbalance model which calculates surface runoff considering vertical and lateral fluxes, both driven by the set of 36 monthly climatological normals and designed to allow very fast global numerical evaluation.

The Tolerable Windows Approach (TWA) to Integrated Assessments (IA) of global warming is based on external normative specifications of tolerable sets of climate impacts as well as proposed emission quotas and policy instruments for implementation. In a subsequent step, the complete set of admissible climate protection strategies which are compatible with these normative inputs is determined by scientific analysis. In doing so, minimum requirements concerning global and national greenhouse gas emission paths can be determined. In this paper we present the basic methodological elements of TWA, discuss its relation to more conventional approaches to IA like cost–benefit analyses, and present some preliminary results obtained by a reduced-form climate model.

A simple model has been designed to describe the interaction of climate and biosphere. Carbon dioxide, understood as a major emitted gas, leads to a change of global climate. Economic interpretation of the model is based on the maximisation of the global CO2 cumulative emissions. The two most important profiles of emission have been obtained: optimal and multi-exponential suboptimal profiles, each displaying different characteristics.

Global Change as a recently emerging, multidimensional problematique shows a variety of world-wide core problems like soil erosion, water scarcity or development disparities that threaten humankind and its future. Sustainability as the encompassing issue for this future is endangered by negative trends and their reinforcements within the Earth System. The understanding of these trends and interactions driving Global Change is a difficult but necessary scientific task, demanding integrative, cross-sectoral research strategies. What are the key problems humankind is facing today? How do they interact? What options do we have for future development, regarding natural boundary conditions and socio-economic constraints? Which types of actual developments might lead to catastrophes? In this article an integrative, transdisciplinary approach to analyze Global Change is presented, which is supposed to provide a novel cognitive basis for politics and the general public to make decisions about the future management of planet Earth. Abstract & Keywords → p. 79

Publisher Summary Most environmental, ecological, and human processes exhibit characteristic scales, which are also called “grain.” A characteristic scale can be defined as the typical extent or duration over which a process has impacts. If the impact of processes is assessed at scales significantly smaller than their characteristic scale, then there is a very large danger of misinterpreting a system's behavior. One important general scale issue is the “scaling” issue—that is, the way variables and their values are translated from one scale to another. Some variables can be scaled in a very straightforward way. These variables are scale-independent, additive, or linearly scaled. The chapter discusses qualitative–quantitative scenarios that are considered by some to be the most powerful tool for communication between science and policy-making. This type of scenarios combines narration, in the form of storylines, with quantitative interpretations of the storylines that are mainly done by mathematical modeling. In scenario development, the term “large scale” means having a numerically greater extent or duration than something with a “small scale.”

This paper outlines the qualitative components (the storylines) of the Millennium Ecosystem Assessment (MA) scenarios. Drawing on a mixture of expert knowledge, experience, and published literature, we have explored plausible consequences of four trajectories for human development. The storylines have been designed to draw out both benefits and risks for ecosystems and human well-being in all four trajectories with enough richness of detail to allow readers to immerse themselves in the world of the scenario. Only a summarized version of the storylines is presented here; readers are encouraged to read the more detailed versions (MA 2005). Together with the quantitative models (Alcamo et al. 2005) the storylines provide a base from which others can consider implications for policy and practice in more depth, adding their own interpretations, experience, and imagination. This is the purpose of the following papers in this volume.

This paper provides an overview of what the Millennium Ecosystem Assessment (MA) calls "indirect and direct drivers" of change in ecosystem services at a global level. The MA definition of a driver is any natural or human-induced factor that directly or indirectly causes a change in an ecosystem. A direct driver unequivocally influences ecosystem processes. An indirect driver operates more diffusely by altering one or more direct drivers. Global driving forces are categorized as demographic, economic, sociopolitical, cultural and religious, scientific and technological, and physical and biological. Drivers in all categories other than physical and biological are considered indirect. Important direct drivers include changes in climate, plant nutrient use, land conversion, and diseases and invasive species. This paper does not discuss natural drivers such as climate variability, extreme weather events, or volcanic eruptions.

It is appropriate to consider water quantity and water quality as two facets of water resources. Both facets are intimately connected to the hydrological cycle, which itself is a component of the Earth’s climate System. Since human activities and health are so connected to water resources, it is essential to determine how far into the future we can predict the condition of the water resources of a region with a sufficient level of confidence. When predictions are not possible, resilience must be built into a water System so that human (and natural) needs are not negatively affected. Even when skillful predictions are possible, they are seldom completely accurate. Thus uncertainty needs to be included when scientific analyses and predictions are used for water resource planning and management, particularly for issues such as adaptation or risk management. The prediction of weather and climate are essential aspects of planning for water resources in changing environmental conditions.

Increasing concerns about the potential risks involved in anthropogenic climate change over the past ten years have boosted the intensity of research efforts on all aspects of the problem and motivated an integrated analysis of their results. This paper is intended to provide a short overview of modeling approaches to integrated assessments of climate change. It also presents an innovative concept, the Tolerable Windows Approach (TWA), as it is adopted in a new research project called Integrated Assessment of Climate Protection Strategies (ICLIPS) at PIK. The approach is based on an inverse modeling concept that derives climate stabilization objectives from perceived unacceptable impacts and produces complete sets of permitted emission paths satisfying the corresponding climate change constraints. Initial results show that the approach is a promising new direction in integrated modeling.

Scientists working in the field of global warming are subject to the increasing tension between soundly based scientific research and the political necessity for the formulation of adequate climate protection strategies. This narrow route between Scylla and Charybdis, which has to prevent science both from withdrawing into its traditional ivory tower and becoming lost in the maelstrom of unbased political claims, demands a well-defined borderline between normative settings and the strict analysis of the Earth System. The borderline is sketched in Article 2 of the Framework Convention on Climate Change (FCCC): “… stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened, and to enable economic development to proceed in a sustainable manner” (UN, 1992; emphasis added). It is the task of science to find out how this political constraint can be fulfilled. It is important, however, to keep in mind that — similar to Odysseus — the route outlined by Article 2 is subject to continuous corrections and thus has to be followed by fuzzy control. This is due both to the fact that norms, settings, and society itself are changing quite rapidly, and to the uncertainties in the knowledge of the mechanisms of the system.