New Road Map Charts the Research Needed Before Any Decision on Solar Geoengineering

Reflective, a San Francisco-based nonprofit that funds research into solar geoengineering, has published a detailed road map of the experiments, studies and infrastructure it says would be needed to make informed decisions about the technology. Scientists have spent half a century exploring whether releasing reflective particles into the stratosphere, mimicking the cooling effect of volcanic eruptions, could help counteract climate change. The approach is known as stratospheric aerosol injection (SAI).

"Our mission is to equip the world with the data and tools required for informed decision-making about sunlight reflection fast enough to matter," said Dakota Gruener, Reflective's cofounder and chief executive. If the research were done in a coordinated way, the road map estimates it would take about a decade and cost around $370 million. Done without coordination, it says the same work would take roughly 20 years and cost nearly $1.4 billion.

The idea remains controversial. Since 2002, hundreds of academics have signed an open letter calling for a ban on outdoor solar geoengineering experiments and an international non-use agreement. "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?" said Aarti Gupta, a co-initiator of the non-use campaign and professor of global environmental governance at Wageningen University in the Netherlands.

The road map's first phase, called foundational knowledge, calls for computer simulations and lab experiments on how the technique could affect regions, ecosystems, ocean circulation, ice sheets and crop yields. This stage would last two to three years and cost $30 million to $75 million, the report says.

The next phase proposes using modified aircraft to release 10 metric tons of sulfur dioxide into the stratosphere, four times over two seasons, in a stage lasting four to eight years and costing $70 million to $150 million. Reflective, incorporated in late 2023, has already raised more than $20 million and funded several dozen research groups.