Could a Global Atmospheric Spraying Program Really Work?

These are the main conclusions of the new research published today in Letters of research on the environment, which examined the capabilities and costs of different sulphate supply methods in the lower stratosphere, known as stratospheric aerosol injection (SAI).

Researchers examined the costs and practicalities of a large-scale hypothetical "solar geo-engineering" project, starting in 15 years. Its goal would be to halve the increase in anthropogenic radiative forcing by deploying materials at an altitude of about 20 kilometers.

They also discussed the possibility of keeping such an idealized program.

Dr. Gernot Wagner, of the John A. Paulson School of Engineering and Applied Science at Harvard University, is co-author of the study. He said: "Solar geoengineering is often described as" fast, cheap and imperfect ".

"Although we do not doubt the opportunity of the ISC, we show that a hypothetical deployment program in 15 years, while being very uncertain and ambitious, would be technically possible strictly to the point of Engineering view: remarkably cheap, with an average of about 2 to 2.5 billion dollars a year over the first 15 years. "

Researchers confirm previous studies of the low direct costs of a potential intervention in stratospheric aerosol geoengineering, but they arrive at these numbers with direct assistance from aerospace engineering companies by specifying what the paper calls "SAI Lofter ( SAIL). "

Wake Smith, co-author of the study, is a lecturer at Yale College. He previously held the positions of CEO of Pemco World Air Services (Senior Aircraft Modification Company), Operations Manager of Atlas Air Worldwide Holdings (Global Freight Company), and Chairman of the Airline Training Division. Boeing flying. "I became intrigued by the technical issues surrounding SAI and by the many studies that claim to show that modified existing aircraft could do the trick." It turns out that it is not the case. In fact, an entirely new design of the aircraft would be necessary to make SAI reasonable, albeit quite hypothetical, parameters and no existing aircraft requires the combination of altitude and the required payload capacity. "

Mr. Smith said: "We have developed SAIL's specifications with the direct contribution of several companies in the aerospace and power industry, and its weight is equivalent to that of a large aircraft in the United States. narrow-body passengers, but to ensure a level flight of 20 km, you need to roughly double the wing of an airliner of equivalent size, and double the thrust, with four engines instead of two.

"At the same time, its fuselage would be stocky and narrow, and sized to accommodate a heavy but dense mass of molten sulfur rather than the large volume of space and air required for passengers."

The team estimated that total development costs would be less than $ 2 billion for the cell and an additional $ 350 million for the modification of existing low-bypass engines.

The new aircraft would include a fleet of eight vehicles in the first year and a little under 100 vehicles in the next 15 years. The fleet would do just over 4,000 missions a year in the first year, reaching just over 60,000 missions a year in the 15th year.

Mr. Wagner said: "Given the potential benefits of halving the predicted average increases in radiative forcing from a given date, these numbers evoke" the incredible economics "of geoengineering dozens of countries could fund such a program, not particularly exotic. "

However, according to the authors, this should not reinforce the often-held fear that a rogue country or operator may launch a clandestine ISC program in an unsuspecting world.

Mr. Smith said: "No comprehensive program of SAIs of the magnitude and nature discussed here could reasonably be expected to maintain secrecy.Even our hypothetical deployment schedule for the first year provides for 4,000 flights at an unusually high altitude, in multiple flight corridors in both hemispheres.That is far too much aerial activity to remain undetected and, once detected, such a program could be deterred. "

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More information:
Tactics and aerosol injection costs in the stratosphere during the first 15 years of deployment, Letters of research on the environment (2018). DOI: 10.1088 / 1748-9326 / aae98d