On Thin Ice: Solar Geoengineering to Manage Tipping Element Risks in the Cryosphere by 2040

Tipping elements are features of the climate system that can display self-reinforcing and non-linear responses if pushed beyond a certain threshold (the "tipping point"). Models suggest that we may surpass several of these tipping points in the next few decades, irrespective of which emissions pathway humanity follows. Some tipping elements reside in the Arctic and Antarctic and could potentially be avoided or arrested via a stratospheric aerosol injection (SAI) program applied only at the poles. This paper considers the utility of proactively developing the capacity to respond to emergent tipping element threats at the poles as a matter of risk management. It then examines both the air and ground infrastructure that would be required to operationalize such capability by 2040 and finds that this would require a funded launch decision by a financially credible actor by roughly 2030. Stratospheric aerosol injection is a solar geoengineering method by which tiny particles cast into the stratosphere reflect a portion of incoming sunlight away from Earth. Recent work has demonstrated that SAI may be effective in preventing components of the climate system known as "tipping elements" from collapsing by cooling the atmosphere and thereby preventing the crossing of dangerous temperature thresholds. In particular, many of the highest risk tipping elements reside in the cryosphere and their minimum temperature thresholds are estimated to be passed in coming decades regardless of global mitigation pathways. An SAI program at high latitudes could effectively manage some of the associated risks by cooling the Arctic and Antarctic, thereby preventing tipping elements from collapsing. This paper investigates the ground and air infrastructure that would be required to operate such a solar geoengineering program by the year 2040. We first describe the logistics of such a program, including airport base location choice, plane procurement and modification strategies, and projected costs. We find that infrastructure development for a polar solar geoengineering program would need to commence by 2030 or sooner in order to successfully safeguard cryospheric tipping elements, suggesting that research and decision-making processes for a stratospheric aerosol injection program should be approached with urgency. We risk crossing tipping thresholds in mid-century that mitigation could not prevent, though geoengineering could rescue the situation A polar solar geoengineering program potentially delay or avoid crossing tipping thresholds Polar solar geoengineering capability by 2040 would require a funded program launch by or before roughly 2030