An Assessment of Radiation Modification from a European Perspective
Abstract:The European Transdisciplinary Assessment of Climate Engineering (EuTRACE) project (2012-2014) is funded by the European Commission (EC). In EuTRACE, researchers from the natural sciences, social sciences and the humanities have joined forces to assess various proposed geoengineering techniques concerning their radiative forcing potential and side effects, ethical aspects, economics aspects, as well as governance and regulation aspects. A comprehensive assessment report will be submitted to the EC in autumn 2014.
We will present some highlights of the part of the EuTRACE assessment that deals with the natural science aspects of proposed Radiation Modification (RM) techniques. The techniques considered are: a) Stratospheric Sulfur Injections; b) Marine Cloud Brightening; c) Desert Brightening; d) Vegetation Brightening; and e) Cirrus Cloud Thinning. A large number of publications in the scientific literature has been considered, as well as recently published assessment reports by the Royal Society in the UK and the German Federal Ministry of Education and Research.
Some of the findings of the assessment are:
- Globally averaged, the current anthropogenic radiative forcing could conceivably be offset by the RM techniques considered. The RM techniques could have a significant global effect already after 1 year or less.
- Model simulations consistently show that Solar RM leads to regional imbalances due to different spatial footprints of solar and carbon dioxide radiative forcings. This may have significant consequences for precipitation patterns and the hydrological cycle.
- Very rapid warming is virtually certain if RM were to be stopped abruptly or over a period of one to a few years.
- Model studies of RM usually assume that the techniques are technologically feasible. In fact, the technological challenges are poorly known, and in many cases the physical processes involved are poorly understood.
We will end by discussing key research questions and knowledge gaps.