Reflective Publishes Road Map for Stratospheric Aerosol Injection Research

The organization released its SAI Research Roadmap. Dakota Gruener, Reflective's cofounder and chief executive, said, "Our mission is to equip the world with the data and tools required for informed decision-making about sunlight reflection fast enough to matter." Gruener added, "Our sense is the world may need to make very consequential decisions on timelines far shorter than our research system is prepared for." Gruener said the exercise is intended to guide scientific efforts and encourage philanthropies or government agencies to fund high-priority work and responsibly accelerate research.

The report estimates that if all the work is done in a coordinated way, it would take about a decade and cost around $370 million. If it is not coordinated, it would require roughly 20 years and nearly $1.4 billion.

Scientists have spent decades exploring whether releasing reflective particles into the stratosphere could counteract climate change by mimicking the cooling effects of volcanic eruptions. The approach is known as stratospheric aerosol injection. While at least hundreds of studies have examined it, major gaps remain in understanding how well it would work and what else it might do.

Gruener stresses that Reflective does not advocate using this form of solar geoengineering. The report does make the case for conducting outdoor experiments, which would release successively larger amounts of sulfur dioxide, or materials that would convert into it, in the stratosphere to observe what happens.

That position is controversial. Since 2002, hundreds of academics have signed an open letter calling for a ban on outdoor experiments and an international non-use agreement, arguing that such a powerful technology could never be governed in a globally equitable way. Some signatories argue that more studies can never address one of the biggest questions about using solar geoengineering: who gets to do it. Aarti Gupta, co-initiator of the non-use initiative and professor of global environmental governance at Wageningen University in the Netherlands, said, "The first-order questions, from my perspective, are not technical. The core question is: Who would control a planet-altering technology like stratospheric aerosol injection? Who would develop it, and who would deploy it, and to what end? To serve what purposes, and whose purposes? Those questions are very fundamental, because this planet-altering technology will have winners and losers."

Reflective was incorporated in late 2023 and has quickly become an important player in solar geoengineering research. It has raised more than $20 million from prominent charities and individuals and provided around $4 million to several dozen research groups. It has also developed an open-source solar geoengineering simulator and an online hub for collaborative research. Earlier this year, Reflective released its SAI Uncertainties database, identifying scientific unknowns and engineering obstacles that would need to be addressed before even a small-scale solar geoengineering effort could move ahead. Among the biggest uncertainties are what gas or particles would make the most sense to use and what would happen once they were released in the dry stratosphere. It is not clear, for example, whether they would spread out in a way that maximizes reflectivity or clump together and quickly fall out into the troposphere, the lowest layer of Earth's atmosphere.

The road map builds upon the database and highlights a path to addressing most of those questions. Its initial phase, labeled "foundational knowledge," includes additional computer simulation studies and lab experiments designed to shed light on potential impacts on different regions, ecosystems, and phenomena, including ocean circulation patterns, ice sheets, and crop yields. The report also notes the need to begin developing more observational tools during this phase to improve understanding of the baseline conditions of the stratosphere and, in turn, the ability to assess any effects from the eventual release of materials. This first stage would last two to three years and cost $30 million to $75 million.