Can Geoengineering be a Plan B (or C or Z) for Climate?

The recent climate summit in Baku has been deemed a failure by many and coupled with our recent crossing the 1.5C temperature target laid out in the Paris Agreement has amplified concerns that we won’t be able to cut greenhouse gas emissions sufficiently quickly to prevent catastrophic climate change. As a result, there has been increased interest in ‘geoengineering’ or ways to cool the planet more rapidly, which may help buy us some time to shift away from fossil fuels. The definition of geoengineering is contested but in the first place it usually refers to directly engineering the planet such as by reflecting more sunlight away from the planet so less heat is absorbed in the first place such as by firing sulphate aerosols into the upper atmosphere. More broadly, the term can also include planetary-scale greenhouse gas removals whether by enhancing ocean sinks, capturing CO2 directly from the air or planting many billions more trees. However, the mere possibility that there are geoengineering options available that would one day avoid the need to take meaningful action on reducing emissions may discourage individuals and firms from taking action, what some term a ‘moral hazard’ or more simply mitigation deterrence. Others object to describing geoengineering as a moral hazard. Partly for moral hazard reasons, some scholars oppose even conducting research into geoengineering. By contrast, the new UK research agency ARIA has begun to develop a world-leading programme exploring different geoengineering options.

How important is problem definition in this case? What do you see as the biggest dangers (and benefits) of beginning to investigate geoengineering? What about small-scale deployment? large-scale deployment? Are there ever legitimate reasons for not carrying out research?