A Planetary Cooling Hose

Abstract

Geoengineering may offer a way to pause global warming, providing the time for more permanent solutions to become effective. Erection of a high-altitude hose offers an affordable and near-term approach to deliver sulfur-bearing fluids to the stratosphere in order to perform geoengineering via solar radiation management. We discuss the design of a hose extending to an altitude of 20 km and sized to deliver 100 ktons of sulfur per year. The sulfur, in the form of H$_2$S, is pushed up the hose by a pump on the ground and then sprayed out at the top, forming H$_2$SO$_4$ aerosols which scatter enough sunlight to perform geoengineering. Because the hose operates continuously, it only has to deliver about 50 gallons/minute (little more than a garden hose). The flux from a single hose is not sufficient to stop global warming by itself, but is enough to test the effect of the aerosols, and, once replicated to about 20 sites across the planet, can offset all the warming caused by atmospheric CO$_2$. Two varieties of hose are presented here, one delivering H$_2$S as a liquid and the other as a gas. Pumping liquid H$_2$S through a narrow 20 km hose requires high pressure, which can be handled by strong and lightweight hose walls or by placing intermediate pumps along the hose. The hose is held up by a suite of balloons, either all at its top, or with some placed along its length as well. The greatest challenge in suspending such a hose is wind, which if not dealt with properly (by streamlining both the balloons and the hose) will collapse the hose. The wide hoses needed to deliver gaseous H$_2$S are particularly susceptible to wind, so must be enclosed within lightweight aero-shrouds to reduce wind forces. After treating the design of these two hoses, we lay out the steps needed to develop and fabricate them, and conclude with some thoughts on how the hoses might be fielded.