Ignorance Is Not an Option: Why NRDC Is Engaging on Solar Geoengineering
The climate crisis may be moving faster than our ability to respond. One controversial tool could potentially buy us time—if we’re ready.
Efforts to reduce greenhouse gas emissions are falling far short of what is needed, making it almost certain that the world will exceed the Paris Agreement goal to limit global temperature rise to 1.5 degrees Celsius above preindustrial levels—potentially within the next five years.
We thus find ourselves on the cusp of the “overshoot era,” a period when global temperatures consistently exceed that 1.5-degree Celsius threshold before hopefully being brought back down through concerted and sustained action. Every additional fraction of a degree we overshoot—and every year we stay there—deepens the damage. That makes it all the more urgent to pursue every viable tool and pathway back to climate stability.
Rapidly and aggressively cutting all greenhouse gas emissions remains the bedrock of any serious climate strategy. Efforts to cut carbon dioxide emissions should be paired with urgent action on short-lived climate pollutants like methane and hydrofluorocarbons, which break down relatively quickly and thus can provide meaningful near-term cooling relief.
But mitigation alone is no longer enough because, even if we stopped all emissions today, the carbon dioxide released to date would continue warming the planet for generations. Carbon dioxide removal—through a combination of natural approaches like ecosystem restoration or technological ones like direct air capture—is essential to forging a path back below 1.5 degrees Celsius.
In addition, we must build resilience. Extreme heat, flooding, wildfires, and other climate impacts are already displacing people, harming public health, and deepening racial and social inequalities. Anticipating those impacts and investing in adaptation is no longer a last resort—it’s a necessity.
Each of those efforts deserves its own serious treatment, and NRDC is committed to all of them. But one piece of the overshoot puzzle has received far less attention than it deserves. That’s solar radiation management (SRM), which NRDC believes deserves careful research and governance.
What is solar radiation management and why does it matter now?
SRM refers to a set of approaches designed to reflect a small fraction of incoming sunlight back into space, temporarily reducing global average surface temperatures. The most prominent of these approaches is stratospheric aerosol injection, which would disperse reflective particles in the upper atmosphere—thereby mimicking the temporary cooling seen after large volcanic eruptions like that of Mount Pinatubo in 1991.
Importantly, SRM is not a cure-all. It does not reduce carbon dioxide or other greenhouse gas levels in the atmosphere and abruptly stopping it without large reductions in greenhouse gas emissions could trigger “termination shock”—a rapid warming as the cooling effect disappears while greenhouse gas concentrations remain high. But if thoroughly researched and carefully governed, SRM could help to keep climate harms in check and buy us valuable time as the world drives toward genuine climate stability. That possibility is worth taking seriously.
Solar radiation management—also known as solar geoengineering—encompasses several distinct approaches to reflecting sunlight, with the most well known being stratospheric aerosol injection and marine cloud brightening.
The real comparison: SRM vs. unchecked warming
Assessing SRM requires honest risk-risk thinking. The relevant question is not whether SRM carries risks—it does—but how those risks compare to the consequences of continued warming. Answering that question requires much more research to understand how SRM might work in practice and what trade-offs it might entail.
NRDC’s position: Yes to research and governance; no to deployment
That research is already underway, supported by government and private sector funding, but it needs to go further and faster. NRDC has been supportive of SRM research for more than a decade, but we oppose any consideration of deployment at this time; the science is too uncertain, and the governance infrastructure is too nascent. That is precisely why now is the moment to invest in both. We need to understand whether SRM is a viable option—and what its real risks and benefits are—before the climate crisis reaches a point where the pressure to deploy it outpaces our ability to make that decision wisely.
We also need governance frameworks to ensure that research is conducted with transparency, appropriate guardrails, and equitable representation. Without that foundation, even well-intentioned research can erode public trust—and lost trust could trigger a backlash that shuts down research before we have the understanding we may urgently need.
It’s for that reason that NRDC recently helped colaunch the Solar Geoengineering Research Governance (SGRG) platform alongside the American Geophysical Union; the Council on Energy, Environment and Water; and the Alliance for Just Deliberation on Solar Geoengineering. SGRG will provide practical tools and support to help institutions conduct SRM research responsibly and in accordance with widely accepted governance principles.
When governance keeps pace with science, research earns the public trust that any legitimate deployment decision would ultimately require. Good governance is not a brake on science. It’s what makes science credible.
Why engagement matters
Some will argue that engaging with SRM is a distraction from mitigation—or worse, that it could give polluters license to keep polluting. We take that concern seriously, and we are unequivocal that SRM is not an alternative to cutting emissions. But avoiding the issue will just increase the potential for decisions about SRM to be made without the voices that have long advocated for science in the public interest and equitable outcomes. The responsible course is to advocate for rigorous and transparent research with strong governance, so that decisions about whether and how SRM might ever be used are informed by the best available science—not left to those with the resources to fund it on their own terms. (And it’s pretty cheap, increasing the likelihood that someone may try.)
Ignorance is not bliss. When the stakes are this high, failing to understand a potentially critical tool is a risk we cannot afford to take.
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