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Office of Technology Assessment at the German Bundestag Office of Technology Assessment at the German Bundestag

Information on the project


Geoengineering (or climate engineering) is a general term for deliberate large-scale interventions in (bio-)geochemical processes of the Earth in order to counteract a possible global warming. In addition to efforts made to reduce greenhouse gas emissions (mitigation strategies) and to adapt to the climate change (adaptation strategies), proponents propagate geoengineering interventions as a third complementary or alternative climate protection strategy or as one that is to be applied in case of an emergency. Already in the 1970s, it has been suggested to inject sulfur aerosols in high atmospheric layers in order to achieve a cooling effect on the climate. Meanwhile, a whole series of most different ideas and concepts has been presented which recently gave cause for intensified debates among experts and in the public.

Background and central aspects of the topic

The proposed concepts can be divided in two large groups: On the one hand, the idea is to influence the global radiation budget (Solar Radiation Management, SRM) in such a way that either less solar radiation strikes the Earth (e.g. shading by sun shades orbiting around the Earth) or that a larger part of the impinging radiation is reflected (e.g. by delivering sulfur aerosols or aluminum nanoparticles into the stratosphere or by artificial cloud stimulation).

On the other hand, interventions in the CO2 cycle are conceivable in order to decrease the atmospheric content of carbon dioxide and thus to mitigate the greenhouse effect. Those are e.g. concepts regarding large-scale fertilization of oceans (e.g. with iron) in order to stimulate phytoplankton growth and thus the absorption of carbon dioxide or to convert biomass into stable carbon compounds (»biochar«) which are applied on a large scale in order to ameliorate degraded and low-fertility soils and which thus might contribute to reduce the concentration of carbon dioxide in the atmosphere. The direct technical removal of carbon dioxide from the atmosphere by means of »artificial trees« (air capture) is another example.

An intervention in global cycles which determine our climate will necessarily involve profound impacts and might entail long-term consequences for ecological and socio-economic systems which are difficult to foresee and can hardly be controlled. Up to now, geoengineering concepts have been discussed focusing mainly on technology and natural sciences (feasibility, climatic impact, environmental risks and consequences etc.), whereas less attention has been paid to aspects regarding ethics, socio-economics, (international) law, politics etc. In view of profound and possibly unintended consequences, several questions of social relevance arise which have to be answered before concretely implementing interventions in the Earth's CO2 cycle or radiation budget.

Science has only just started to deal with these and other questions so that there is still a considerable lack of knowledge. However, these issues have already been the subject of first political debates (e.g. in a series of hearings in the British Parliament as well as in the US Congress since autumn 2009), because the political pressure to decide is rising tangibly. Against this background, TAB has been commissioned by the Committee on Education, Research and Technology Assessment of the German Bundestag to carry out a TA project with regard to the topic of »Geoengineering«.

Objective and procedure

On the one hand, the objective of the TAB project is to give a comprehensive overview of the current state of knowledge with regard to technological and natural scientific aspects of the different geoengineering concepts proposed. On the other hand, the objective is to discuss the facets of these concepts in terms of (international) law, ethics, socio-economics and politics.

The project is divided into three parts:

Interventions in the CO2 cycle

This work package deals with concepts and technologies enabling interventions in the CO2 cycle. Besides new technologies such as »artificial trees«, also potential methods and procedures from the fields of land use, agriculture and forestry are discussed, some of which are already applied in niche areas. The effectiveness regarding CO2 mitigation as well as the costs, risks and environmental impacts of the different technologies and procedures will be described and the need for further research will be identified. This work package will be complemented by a classification of the possibilities of using the carbon dioxide gained from the atmosphere or from flue gases of industrial plants for reasonable products and applications in order to contribute to CO2 mitigation.

For this work package, it is possible to refer to comprehensive preliminary work within the framework of the currently ongoing TAB project Technical options for managing the CO2 cycle, the results of which should be integrated into this project with regard to a consistent reporting.

Manipulating the global radiation budget

Within the framework of this work package, the procedures and concept proposals for manipulating the global radiation budget will be examined. With regard to the different technologies, the objective is to evaluate their potential of lowering the global temperature as well as to identify the costs, risks and environmental impacts involved. As many of these technologies currently are only existing as a mere idea or still are at the stage of basic research, another focus of the work package is to identify gaps of knowledge as well as the need for research involved.

Regulation, evaluation and public discourse on geoengineering interventions

The objective of this work step is to identify and to discuss the relevant ethical, legal and political issues arising in the context of a large-scale research on and implementation of geoengineering measures. Here, particular attention will be paid to an interdisciplinary and internationally comparative perspective.

In detail, the objectives within the framework of this work package are

  • to analyze the existing situation in terms of (international) law,
  • to identify possible needs and options for regulation,
  • to broach issues of risk assessment and communication,
  • to discuss potential evaluation approaches and decision criteria as well as
  • to describe the debate concerning geoengineering in the media, in the public and in politics.