Ambivalence in calculating the future: the case of re-engineering the world

Recently, climate engineering and particularly sulphur aerosol injection (SAI) have entered the arena of international climate change politics. The idea behind SAI is very simple: to reflect sunlight and heat back into space by injecting particles into the stratosphere. SAI has the theoretical potential to moderate anthropogenic climate change in a timely fashion and at very low costs but may also cause major environmental harm. Determining the future of SAI will entail dealing with many major uncertainties such as assessing risks, costs and benefits. This paper critically investigates scientific knowledge production under conditions of major uncertainty. It discusses how uncertainty, ethics and social considerations are treated in the SAI literature, which applies techno-economic models. In the simplest studies, important uncertainties are excluded from the models, but the more complex studies include many uncertainties, which may have considerable influence on the results and recommendations. In some cases the modelled results are overshadowed or strengthened by ethical discussions or methodological reflexivity that emphasize uncertainties and model limitations. There seems to be ambivalence between constructing certainty, on one hand, and an awareness of methodological limitations, on the other. Finally, the value of these papers for decision-makers and other concerned groups is discussed.