Interest in governing experiments to alter Earth’s climate is growing as scientists increasingly look at geoengineering to slow global warming.

From cooling the atmosphere with special aerosols to sucking carbon dioxide out of the air, scientists have proposed a number of technologies that could potentially alter the climate system and reverse temperature increases.

For now, they’re mostly theoretical. But with scientific interest quickly growing, and some high-profile experiments planned in the near future, some experts say the possibility of large-scale geoengineering projects is no longer a fantasy.

Because of their potential global impact—and the risks if something should go wrong—world leaders may be long overdue for a talk about how the international community should regulate geoengineering.

Some organizations are trying to get the ball rolling immediately. Yesterday, the Carnegie Climate Geoengineering Governance Initiative (C2G2)—a project of the Carnegie Council for Ethics in International Affairs—presented a briefing to the U.N. Environment Programme’s Committee of Permanent Representatives. It outlined the need for international agreements on geoengineering technology.

Then, this morning, the group hosted an extra workshop exploring different ways that geoengineering projects might be governed, and the factors that should be taken into account when considering them.

According to David Keith, a Harvard University engineer and a member of C2G2’s advisory group, these types of conversations would have been timely a decade ago.

“We don’t make decisions well in crisis, in general,” he told E&E News. While it may be decades before global-scale geoengineering projects become a major possibility, “it takes a long time to have these conversations,” he said.

Questions for the globe

There are two major categories of global climate geoengineering, each with different regulatory concerns.

The first is carbon removal, the use of special technology to suck carbon dioxide out of the atmosphere, lowering global temperatures in the process. The most discussed method involves using huge tree plantations to naturally suck up carbon dioxide, then harvesting the trees for energy and collecting their carbon emissions with carbon-capture technology—making the whole process carbon negative.

Many of the uncertainties around carbon removal center on the sheer amount of land, water and other natural resources the process would require at a large scale. These are important concerns—but because these types of resource issues are typically handled at the country level, the regulation of carbon removal technology may mainly be an issue for national governments to resolve on an individual basis.

On the other hand, solar geoengineering—the other major category—may present some big questions for the international community to address together. Solar geoengineering would use technology to reduce the amount of sunlight that reaches the Earth’s surface, thus cooling the planet. Some of the most commonly proposed strategies involve spraying reflective aerosols high into the atmosphere, where they would reflect sunlight away from the Earth.

Some scientists are concerned that there could risks associated with solar geoengineering—unintended effects on the weather, for instance, or damage to the planet’s protective ozone layer. Because most research on solar geoengineering has been restricted to modeling studies, there’s disagreement among experts about the possibility, or seriousness, of these potential side effects.

Keith, himself a specialist on solar geoengineering, believes the science so far suggests these risks are “small.” He and other Harvard scientists, including atmospheric chemistry expert Frank Keutsch, are planning a series of small-scale field experiments. It’s the first of their kind, and the researchers hope they will provide more information on the physical behavior of aerosols in the atmosphere.

These experiments may have sparked some of the discussion around the need for geoengineering governance. While small-scale tests likely carry little risk, they’ve introduced the idea that solar geoengineering may be moving from theory to reality.

Another, perhaps bigger, concern about solar geoengineering revolves around what might happen if we start doing it—and then stop. Aerosols don’t last forever in the atmosphere, and nations would have to periodically spray them into the air to maintain the reflective layer. In theory, if they stopped doing it, the aerosols could fall out of the atmosphere, and global temperatures would begin to rise again. It might happen quickly, posing serious consequences for communities and ecosystems that don’t have time to adjust.

Discussing these risks, and having a plan in place to manage them, would be one major function of an international dialogue on geoengineering, C2G2 suggests.

More generally, “there’s also the question of what if countries really disagree about the extent to which these technologies should be used,” Keith pointed out. If a global agreement is the goal, it could take years to hammer out an agreement. So it’s better to begin now, Keith said, before the technology reaches a point where it could be deployed unregulated.

Pushing for an agreement

Reaching an international agreement is C2G2’s priority at the moment. Regarding solar geoengineering, in particular, its formal approach, presented yesterday to the U.N. Environment Programme, calls for “international agreements to help prevent the deployment of solar geoengineering unless (i) the risks and potential benefits are sufficiently understood, and (ii) international governance frameworks are agreed.”

The U.N. Environment Assembly, it says, could produce a resolution to this effect by next year.

Keith, for his part, is skeptical of the need for a specific international protocol for geoengineering research. He argues that it’s important not to stifle science in up-and-coming areas, as long as it’s safe and ethical.

“I think it’s really important that research be, as much as possible, more open—that there be a high level of transparency about research funding, about research goals, that it not be militarized,” he said. "I’d love to see more international cooperation, including through climate agencies like the WMO [World Meteorological Organization] that coordinate international research on climate. That, I think, is really useful.”

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at