New research shows that methods for slowing climate change — from planting forests to fertilizing the oceans with iron – bring dangerous risk tradeoffs

To slow down the accelerating pace of climate change, scientists are working on radical geoengineering technologies like space mirrors, ocean iron fertilization, and cirrus cloud thinning to tweak the earth’s climate system. But a new study published in the journal Risk Analysis finds that none of these human interventions are risk free. Instead, “they merely shift risk or redistribute it,” says lead author Benjamin Sovacool, professor of energy policy at the University of Sussex Business School and a professor at Aarhus University and Boston University. “These risk tradeoffs must be evaluated if some of the more radical geoengineering technologies are to be deployed.” 

In an analysis of original interviews with 125 experts in 21 countries, Sovacool and his team identified the risks of deploying 20 different climate geoengineering options. Half of those options focus on removing carbon dioxide or greenhouse gasses from the atmosphere (sometimes termed “carbon removal”); the other half focus on solar radiation management (limiting the amount of sunlight reaching Earth and reflecting it back into space). Some of the methods are already being implemented around the world (soil management, ecosystem restoration, and afforestation). Others are in the midst of being scaled up (direct air capture, enhanced weathering, and bioenergy with carbon capture and storage).

All of the experts interviewed between May and August 2021 had published peer-reviewed research or related patents and intellectual property on climate geoengineering technologies within the past 10 years. They included both advocates and critics of the technologies. Among other questions, experts were asked: What risks do the deployment of these options entail? What types of tradeoffs may emerge through their deployment? The final data set consisted of a structured coding of the interview data, along with numerical information such as how many participants touched on a particular theme or technology, or how often such a theme or technology was discussed in total.

An analysis of the results showed that “every climate geoengineering option has one type of risk that it trades off with,” says Sovacool, who is also an author of the latest (2022) report from the Intergovernmental Panel on Climate Change (IPCC). For example, options like high-altitude sunshades or stratospheric aerosol injection balance the risks of capacity building with weaponization. “The more you distribute capacity and infrastructure, the more it might lead to weaponization risks or security threats,” says Sovacool. One expert stated that “options like these” depend upon the expansion of an aerospace or space industry are a security risk, as you are bringing high-tech space industries into countries that don’t normally have them.  Players gain new capabilities that they didn’t have before, and these could spill-over into an arms race or new technology in the hands of new actors could become military or hostile.”

The study includes dozens of qualitative quotes from the experts interviewed – addressing specific risk-risk tradeoffs within each category. Even low-cost carbon storage options like afforestation or ecosystem restoration balance carbon storage potential vs. ecosystem health and functionality. As one participant put it, afforestation and ecosystem options “need far more land and irrigation if you do it naturally without fertilizers, making it better for local ecosystems, but if you want to double or triple yields, you have to introduce nitrogen fertilizers, which are bad for the environment.”

Sovacool and his colleagues created a framework that clusters the risk-risk tradeoffs into three categories: institutional and governance, technological and environmental risk, and behavioral and temporal. “Our results illustrate a complex and interlocking number of risks,” says Sovacool. Under the institutional and governance category, they identify a risk-risk tradeoff of urgency vs. safety. The authors write that “the urgency and immediacy of addressing climate change could generate a powerful incentive to deploy geoengineering options as soon as possible—but this also means there will be fewer tests, possibly less stringent safety protocols, and greater uncertainty about their impacts.”

The study identifies a total of 12 risk-risk tradeoffs in climate geoengineering that must be weighed against the risks of climate change itself — particularly if some of the more radical options are to be employed. “It will be very hard to manage some of these tradeoffs — for example, weaponization or social backlash,” says Sovacool. “This may make some options unmanageable.” Still, the authors argue, “While these approaches pose risks of their own across different types of populations and ecosystems, they also have the (greater) potential to significantly reduce the pending impacts of climate change to humans.” 

The bottom line, says Sovacool, is that “there is no such thing as zero-risk climate protection.”


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