# The Buying Time Argument within the Solar Radiation Management Discourse
## 4 A Case Study of a BTA Instance  
Due to the generic status of the argument given in the previous section, there are placeholders involved in order to discuss the specific requirements and their fulfillment. As encouraged in the previous section, we will have a closer look on one SAI scenario which counts as an instantiation for the placeholder O (or, to be more precise, for a climate engineering strategy within policy option O). There are, of course, many SAI scenarios to be found in the literature (overview in [37]). We select and focus one specific scenario, since it is specifically shaped to showcase a buying time instantiation of option O (though not under this nomenclature). This scenario has been proposed by [PERSON] and [PERSON] and their colleagues [38; 39]. These authors incorporate the idea of arguing on a case-by-case basis, stating that \"One cannot meaningfully evaluate solar geoengineering without a scenario for its implementation.\" [39] (p. 201). This scenario resonates perfectly with our analysis which asks for a case specific inquiry of the empirical premises of the BT argument. Thus, the SAI scenario of [PERSON] and his colleagues will function as paradigm case study for the further evaluation of the BTA. In their proposal, SAI is used in order to reduce the rate of global temperature change for a given emission trajectory, rather than stop the temperature increase altogether. This scenario is an excellent example for the BTA, for it is designed specifically in accordance with the buying time and peak-shaving approach: \"At a minimum, introducing [the proposed SAI scenario] would increase the amount of time to both learn and adapt; by reducing the needed rate for adaptation, it could reduce costs of adaptation\" [38] (p. 2). Here, the cost-reduction perspective (\"least cost planning\") is evident and specified in terms of adaptation (in a broader sense, as we suppose). The temperature increase in the 21 st century will have, even under optimistic mitigation assumptions, a severe influence on life on earth. It is not only the absolute change in global mean temperature, which catalyzes dangerous climate events, but also the rate of warming. The frequency and strength of some climate events are determined by the warming rate. A speedy temperature increase will make adaptation even more difficult [38]. SAI could limit the rate of global temperature rise. This way, the authors argue that SAI could buy time for adaptation measures, writing that, \"In particular, using SRM to limit the rate of temperature change would provide more time for both ecosystems and human systems to adapt to climate changes [38] (p. 11). Buying time now points to adaptation capabilities, broadly conceived. The scenario is designed to meet specific criteria: It has to be temporary, moderate and responsive. These are the normative requirements that guide the scenario setup. They correspond with the requirements being adopted in the previous sections. The technology envisaged by the authors is SAI. Authors assume the radiative forcing of one million tons of sulfur (MTS) to be 0.6-0.8 Wm-2. For a given RCP, the scenario targets at cutting the rate of change of the respective radiative forcing in half. This suggests that the choice of a certain RCP is decisive for the scenario. \"The choice of emissions trajectory has a profound influence over the magnitude and duration of geoengineering required to limit the rate of change of global mean temperature\" [38] (p. 5). For the main part of their investigation and for illustrative purpose, the authors assume RCP4.5 and they calculate the amount of injected sulfur accordingly. In the RCP4.5 pathway, injection would start with 0.035 MtS per year and would increase steadily in the first decade by the same amount. After 10 years, the yearly injection would amount to 0.35 MtS. The rate of injection would be adjusted in order to steady the rate of temperature change (see picture below, second panel).