5. Conclusion
This paper has provided a detailed analysis of the SAI double catastrophe scenario, in which a catastrophic societal collapse induces SAI intermittency. The severity of this scenario depends jointly on the severity of the collapse and the severity of the intermittency. Great uncertainty exists throughout this scenario, especially regarding how effectively collapse survivors could cope with the rapidly rising temperatures of intermittency. However, it is plausible that the double catastrophe could be so severe as to cause permanent destruction of advanced technological civilization or even human extinction. For this reason in particular, avoiding the double catastrophe is an important goal for decision making about greenhouse gas emissions, geoengineering, and global catastrophic risk reduction in general.
One safe conclusion from the SAI double catastrophe scenario is that greenhouse gas emissions reductions would help reduce global catastrophic risk. In the absence of SAI or other geoengineering, emissions reductions help avoid catastrophic climate change impacts (as in Sherwood and Huber 2010). If SAI is implemented, emissions reductions reduce the severity of any possible intermittency. And in either case, emissions reductions help with ocean acidification, which lurks as another possible cause of global catastrophe. On the other hand, it is possible for emissions reductions to increase global catastrophic risk. Perhaps emissions reductions would cause economic decline, leaving society more vulnerable to other shocks. Future research is needed to clarify these possibilities. For now, it appears that emissions reductions would cause a net decrease in global catastrophic risk...
...A more general conclusion that can be reached from this paper is on the importance of considering multiple global catastrophic risks at once. Global catastrophes can have important interaction effects, such as with a catastrophic societal collapse causing SAI intermittency. More importantly, actions we can take now can impact multiple global catastrophic risks, such as efforts to build communities that could be self-sufficient during a variety of catastrophe scenarios. An integrative, systems-based approach to global catastrophic risk analysis is needed to understand these various interactions and how best to reduce the overall risk of global catastrophe.