On intrinsic uncertainties in earth system modelling

Various types of uncertainty plague climate change simulation, which is, in turn, a crucialelement of Earth System modelling. This fact was recognized for example in the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC, Houghton et al. (2001)), where the authors indicate that for the period between 1990 and 2100 an increase of the global mean temperature around 1.4-5.8°C is to be expected (Houghton et al. 2001). The width of this span as well as the fact that the authors did not give a number concerning the most probable value or a probability distribution shows clearly the large uncertainty. This uncertainty does not only arise due to the different scenarios of future development concerning greenhouse gas emissions for example, but follows to large degree from the wide range of results from different models as well. The chain of these uncertainties of imponderables in the analysis of the Earth System (Schellnhuber and Wenzel 1998), which includes the climate system as well as the anthroposphere, reaches from uncertainties about the existence of critical thresholds, to ignorance of the exact state of today's climate, and ultimately to a lack of knowledge concerning climate-relevant processes, some of which are visible as uncertainties in climate models. Many attempts have been made to reduce these uncertainties by gaining a conceptual understanding of processes, e.g. of El Ni~no / Southern Oscillation (ENSO) (Jin 1997, e.g.) or of the Atlantic overturning (Stommel 1961; Rahmstorf 1996, e.g.), by developing methods to identify critical thresholds in the climate system (Alley et al. 2003; Rial et al. 2004, e.g.), or by implementing an increasing number of processes in a model, resulting in high resolution general circulation models (GCMs), e.g. ECHAM5/MPI-OM (Jungclaus et al. 2006) or HadCM3 (Gordon et al. 2000) and many more. Nevertheless, the much larger part of uncertainties is inevitable in the process of modelling as well as in our understanding of the Earth System. In this thesis we will structure this conglomeration of uncertainties climate research is confronted with. We will address several types of uncertainty and apply methods of dynamical systems theory on a trendsetting field of climate research, i.e. the Indian monsoon ...thesi

REMIND-D: A Hybrid Energy-Economy Model of Germany

This paper presents a detailed documentation of the hybrid energy-economy model REMIND-D. REMIND-D is a Ramsey-type growth model for Germany that integrates a detailed bottom-up energy system module, coupled by a hard link. The model provides a quantitative framework for analyzing long-term domestic CO2 emission reduction scenarios. Due to its hybrid nature, REMIND-D facilitates an integrated analysis of the interplay between technological mitigation options in the different sectors of the energy system as well as overall macroeconomic dynamics. REMIND-D is an intertemporal optimization model, featuring optimal annual mitigation effort and technology deployment as a model output. In order to provide transparency on model assumptions, this paper gives an overview of the model structure, the input data used to calibrate REMIND-D to the Federal Republic of Germany, as well as the techno-economic parameters of the technologies considered in the energy system module.Hybrid Model, Germany, Energy System, Domestic Mitigation

Benefits and pitfalls of an EU emissions budget approach

Following the conclusion of the 'Fit for 55' package, European Union (EU) climate policy will enter its next phase. One of the most important decisions will be how to set the economy-wide emissions reduction target for 2040, which will form the starting point for the next round of revisions of all EU climate policy legislation. The European Climate Law stipulates that the European Commission shall propose a 2040 target that is based, among other things, on a "projected indicative Union greenhouse gas budget for the 2030-2050 period", informed by a report of the newly established European Scientific Advisory Board on Climate Change. While cumulating emissions resulting from different future trajectories can help to assess ambition levels, strictly deriving a 'science-based' EU emissions budget from the global carbon budget has several pitfalls. The debate on the design of EU climate policy after 2030 should not put too much focus on the 'appropriate' target for 2040 but on how to further develop the governance architecture, strengthen policy instruments, and bolster public support. (author's abstract

The implications of initiating immediate climate change mitigation - A potential for co-benefits?

Fragmented climate policies across parties of the United Nations Framework on Climate Change have led to the question of whether initiating significant and immediate climate change mitigation can support the achievement of other non-climate objectives. We analyze such potential co-benefits in connection with a range of mitigation efforts using results from eleven integrated assessment models. These model results suggest that an immediate mitigation of climate change coincide for Europe with an increase in energy security and a higher utilization of non-biomass renewable energy technologies. In addition, the importance of phasing out coal is highlighted with external cost estimates showing substantial health benefits consistent with the range of mitigation efforts

Weltklimagipfel in Kopenhagen: Welche Erfolgsaussichten hat ein globales Klimaabkommen?

Auf dem Weltklimagipfel in Kopenhagen im Dezember 2009 wird ein globales Klimaabkommen verhandelt. Können dort Strukturen geschaffen werden, die einen effizienten und kostengünstigen Klimaschutz ermöglichen? Entscheidend sei es, nach Meinung von Hubertus Bardt, Institut der deutschen Wirtschaft Köln, die Klimaschutzziele mit möglichst geringem Kostenaufwand zu erreichen. Möchte man international einen möglichst effizienten Klimaschutz betreiben, müssten die Maßnahmen zur Vermeidung von Treibhausgasemissionen an den Orten vorgenommen werden, wo dies je vermiedener Einheit am billigsten sei. Oftmals dürften diese Möglichkeiten in den Entwicklungs- und Schwellenländern liegen, während in den klimapolitisch aktiven Industrieländern preiswerte Vermeidungspotentiale bereits zu einem guten Teil ausgeschöpft seien. Ein neues internationales Klimaabkommen müsse also dazu beitragen, dass die global günstigsten Vermeidungspotentiale realisiert werden. Ottmar Edenhofer, Brigitte Knopf und Gunnar Luderer, Potsdam-Institut für Klimafolgengforschung, sehen eine sinnvolle Architektur der Klimapolitik hauptsächlich in drei Maßnahmen: 1) in einer Einigung über die Kohlenstoffmenge, die noch bis zum Ende des Jahrhunderts in der Atmosphäre abgelagert werden darf, 2) in der Verteilung der Emissionsrechte nach einem gerechten Schlüssel auf alle Nationen und 3) in der Schaffung der institutionellen Voraussetzungen für einen globalen Emissionshandel. Für Sabine Schlacke, Universität Bremen, scheint das "Ob" und "Wie" eines Post-Kyoto-Abkommens "derzeit mehr als ungewiss". Ein Scheitern der internationalen Verhandlungen könne aber durchaus auch die Möglichkeit eröffnen, über einen Systemwandel bei der internationalen Architektur des Klimaschutzes nachzudenken.Umweltabkommen, Internationale Umweltpolitik, Klimaschutz, Finanzierung, Welt

From Targets to Action : Rolling up our Sleeves after Paris

At the United Nations Climate Change Conference in Paris in 2015 ambitious targets for responding to the threat of climate change have been set: limiting global temperature increase to “well below 2 °C […] and to pursue efforts to limit the temperature increase to 1.5 °C”. However, calculating the CO2 budget for 1.5 °C, it becomes clear that there is nearly no room left for future emissions. Scenarios suggest that negative emission technologies will play an even more important role for 1.5 °C than they already play for 2 °C. Especially against this background the feasibility of the target(s) is hotly debated, but this debate does not initiate the next steps that are urgently needed. Already the negotiations have featured the move from targets to implementation which is needed in the coming decade. Most importantly, there is an urgent need to develop and implement instruments that incentivize the rapid decarbonization. Moreover, it needs to be worked out how to link the climate and development agenda and prevent a buildup of coal power causing lock-in effects. Short term entry points into climate policy should now be in the focus instead of the fruitless debate on the feasibility of targets

Der Emissionsbudget-Ansatz in der EU-Klimapolitik

Nach dem Abschluss des Fit for 55-Pakets wird die Klimapolitik der Europäischen Union (EU) in ihre nächste Phase eintreten. Eine der wichtigsten Entscheidungen wird sein, das übergreifende Emissionsreduktionsziel für 2040 festzulegen, das den Ausgangspunkt für die nächste Runde der Überarbeitung aller klimapolitischen Rechtsvorschriften der EU bilden wird. Das Europäische Klimagesetz sieht vor, dass die Europäische Kommission ein Ziel für 2040 vorschlägt, das unter anderem auf einem "projizierte[n] indikative[n] Treibhausgasbudget der Union für den Zeitraum von 2030 bis 2050" basiert. Dieses Budget wiederum stützt sich auf einen Bericht des mit dem EU-Klimagesetz neu geschaffenen Europäischen wissenschaftlichen Beirats zum Klimawandel. Das Kumulieren von Emissionen, die sich aus verschiedenen Minderungsszenarien ergeben, kann bei der Bewertung der jeweiligen Ambitionsniveaus helfen; dagegen birgt die strikte Ableitung eines EU-Emissionsbudgets aus dem globalen CO2-Budget mehrere Fallstricke. Die Debatte über die Gestaltung der EU-Klimapolitik nach 2030 sollte sich indes nicht zu sehr auf ein »wissenschaftlich angemessenes« Niveau des Ziels für 2040 konzentrieren, sondern darauf, wie die Governance-Architektur weiterentwickelt, die politischen Instrumente gestärkt und die öffentliche Unterstützung für eine ehrgeizige Klimapolitik befördert werden kann. (Autorenreferat

CCS: CO2-Sequestrierung: Ein wirksamer Beitrag zum Klimaschutz?

Die Abscheidung und Lagerung von CO2 wird zunehmend als Option im Rahmen einer Klimaschutzstrategie diskutiert. Wie sicher und wie wirksam ist diese Methode? Ottmar Edenhofer, Brigitte Knopf und Matthias Kalkuhl, Potsdam-Institut für Klimafolgenforschung, Berlin, machen deutlich, dass die Klimapolitik nur dann erfolgreich ist, wenn es gelingt, den Großteil des Bestandes fossiler Ressourcen nicht in die Atmosphäre gelangen zu lassen. Deshalb kann CCS auch nur dann eine Option für den Klimaschutz sein, wenn es einen ambitionierten Klimaschutz gibt. CCS schaffe einen zeitlichen Spielraum, um einen globalen Emissionshandel aufzubauen und in die erneuerbaren Energien zu investieren. Für Bernhard Fischer, E.ON Energie AG, München, bietet die CO2-Abtrennung und Speicherung erfolgversprechende Ansätze. Die damit verbundenen Kosten und das Risiko, diese Technologien marktreif zu machen, seien allerdings erheblich. Deshalb solle die öffentliche Hand finanzielle Unterstützung bei den ersten Demonstrationsprojekten leisten. Manfred Treber und Christoph Bals, Germanwatch e.V., Bonn, unterstreichen, dass »zwar die einzelnen Bestandteile, jedoch noch nicht CCS als Gesamtkonzept den Test bestanden hat, dass es in industriellem Maßstab sicher einsatzfähig ist«. Es müsse vor allem sichergestellt werden, dass die abgetrennten CO2-Mengen dauerhaft sicher in tiefen geologischen Formationen gelagert werden können. Dann erst könne entschieden werden, ob CCS zum Erreichen der Klimaziele beitragen werde. Hans-Jochen Luhmann, Wuppertal Institut für Klima, Umwelt, Energie, setzt sich vornehmlich mit CCS bei Kohlekraftwerken auseinander, die seiner Meinung nur »ein begrenztes und vor allem nur ein zeitlich befristetes Element einer Lösung des Klimaproblems« sind.Klimaschutz, Fossiler Energieträger, Kohle, Emissionshandel, Umweltpolitik

On the Economics of Renewable Energy Sources

With the global expansion of renewable energy (RE) technologies, the provision of optimal RE policy packages becomes an important task. We review pivotal aspects regarding the economics of renewables that are relevant to the design of an optimal RE policy, many of which are to date unresolved. We do so from three interrelated perspectives that a meaningful public policy framework for inquiry must take into account. First, we explore different social objectives justifying the deployment of RE technologies, including potential co-benefits of RE deployment, and review modelbased estimates of the economic potential of RE technologies, i.e. their socially optimal deployment level. Second, we address pivotal market failures that arise in the course of implementing the economic potential of RE sources in decentralized markets. Third, we discuss multiple policy instruments curing these market failures. Our framework reveals the requirements for an assessment of the relevant options for real-world decision makers in the field of RE policies. This review makes it clear that there are remaining white areas on the knowledge map concerning consistent and socially optimal RE policies

Scientific assessments to facilitate deliberative policy learning

Putting the recently adopted global Sustainable Development Goals or the Paris Agreement on international climate policy into action will require careful policy choices. Appropriately informing decision-makers about longer-term, wicked policy issues remains a considerable challenge for the scientific community. Typically, these vital policy issues are highly uncertain, value-laden and disputed, and affect multiple temporal and spatial scales, governance levels, policy fields, and socioeconomic contexts simultaneously. In light of this, science-policy interfaces should help facilitate learning processes and open deliberation among all actors involved about potentially acceptable policy pathways. For this purpose, science-policy interfaces must strive to foster some enabling conditions: (1) “representation” in terms of engaging with diverse stakeholders (including experts) and acknowledging divergent viewpoints; (2) “empowerment” of underrepresented societal groups by co-developing and integrating policy scenarios that reflect their specific knowledge systems and worldviews; (3) “capacity building” regarding methods and skills for integration and synthesis, as well as through the provision of knowledge synthesis about the policy solution space; and (4) “spaces for deliberation”, facilitating direct interaction between different stakeholders, including governments and scientists. We argue that integrated, multi-stakeholder, scientific assessment processes—particularly the collaborative assessments of policy alternatives and their various implications—offer potential advantages in this regard, compared with alternatives for bridging scientific expertise and public policy. This article is part of a collection on scientific advice to governments