Scientists Model Costs of Geoengineering Effort to Dim the Sun

Geoengineering — the deliberate effort to manipulate the Earth’s climate in an attempt to offset, delay, or slow global warming — has slowly transformed from a pie-in-the-sky idea to a serious concept that may well be attempted one day. A wide variety of schemes have been proposed for how we might cool the Earth, but many of these would require the development of technologies far beyond our current capability. Nobody thinks we’ll be deploying solar shades to reduce incoming solar radiation any time soon, for example. On the other hand, the idea of seeding sulfur into the atmosphere is well within our technological grasp today, even if the tools and infrastructure for carrying out this process on an ongoing and planet-wide basis do not currently exist.

Wake Smith, a lecturer at Yale, and Gernot Wagner, a lecturer at Harvard, set out to calculate what it would cost to launch a planet-wide Stratospheric Aerosol Injection (SAI) program, using current best-available data for expected R&D and operational costs. One of their major findings is that early work in this field has been incorrect. It’s been assumed that existing aircraft could be modified to perform the injection role without a need for a new vehicle, but Smith and Wagner communicated directly with aircraft manufacturers and confirmed this isn’t true. No current aircraft meets the combined altitude and payload requirements to disperse the aerosols at ~20km (63,360 feet). They propose the development of the SAI Loader, or SAIL.

The report then steps through the assumed requirements for any geoengineering effort (distribution would be done at four locations north and south of the equator), the development costs associated with various lifting bodies/distribution methods, and the total number of aircraft estimated to be needed to carry out the venture long-term. That’s one of the clear downsides to geoengineering via this method — once we start, we won’t be able to stop unless the conditions on the ground change in such a way as to make the intervention less necessary.

Here’s the team’s conclusion:

Solar geoengineering is often described as ‘fast, cheap, and imperfect. The deployment scenario laid out here assumes the first, though it clarifies that ‘fast’ in this context refers to the immediacy of the impact that would derive from deployment… This paper further confirms ‘cheap,’ but says nothing about ‘imperfect.’ We here make no judgment about the desirability of SAI. We simply show that a hypothetical deployment program commencing 15 years hence, while both highly uncertain and ambitious, would indeed be technically possible from an engineering perspective. It would also be remarkably inexpensive.

Total pre-start costs to launch a hypothetical SAI effort 15 years from now are ~$3.5 billion in 2018 US dollars. A program that would deploy 0.2 Mt of SO2 in year 1 and ramp up linearly thereafter at 0.2 Mt SO2/yr would require average annual operating costs of ~$2.25 billion/yr over 15 years. While these figures include all development and direct operating costs, they do not include any indirect costs such as for monitoring and measuring the impacts of SAI deployment… Estimating such numbers is highly speculative.

The Astronomical Cost of Doing Nothing

On Friday, November 23, 13 federal agencies released Volume II of the National Climate Assessment, a report mandated by law and issued every four years. The 1,656-page report examines climate trends by US geographical regions and evaluates how well existing agricultural and resource management approaches are working. The bottom-line impact of the report is that the cumulative and combined impacts of climate change could collectively slash US GDP by 10 percent by 2100. That’s double the impact of the Great Recession. In 2018 terms, it works out to $1.939T in lost economic productivity.

Numbers like that are why geoengineering is likely to be implemented. As the costs of failing to act continue to climb, the temptation to try measures to cool the planet will only rise. This study demonstrates that the plan is surprisingly feasible, at least as far as costs are concerned, though it takes no position on whether geoengineering should be done. That’ll come later. Don’t be surprised if the eventual answer is yes, despite the risks, costs, and uncertainties.

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