I write this from a smoke-filled Northern California apartment, breathing thick, ashy, overheated air as heat waves shatter records and glaciers collapse against the backdrop of a rapidly changing climate. With emotions and particulates burning in my chest, it feels darkly ironic that my current line of work involves injecting the (computer-simulated) atmosphere with even more particles to avert climate disaster.  

I work (now remotely) in Harvard’s Solar Geoengineering Research Program, investigating the effects of aerosol-based marine cloud brightening on weather and climate dynamics. Solar geoengineering, also called solar radiation management (SRM), refers to deliberate alteration of Earth’s upper atmosphere and clouds by adding particles that reflect a small fraction of sunlight to offset warming from greenhouse gases. Though strictly theoretical, this research naturally draws controversy: lofting particles into the atmosphere as a last-ditch effort to cool the planet is a deeply unsettling concept. 

To be abundantly clear about this research in the context of the climate crisis, cutting emissions is indisputably first priority. SRM is not a solution to climate change ― if anything, it is an emergency band-aid. Ending the fossil fuel economy and decarbonizing energy are immediately necessary (read: several decades overdue). But since excess greenhouse gases have accumulated in the atmosphere, even if emissions miraculously reach zero today, current and future generations will not be spared the consequences of inheriting an unstable climate.

It is this daunting reality ― that the best-case scenario still poses major hazard for generations to come ― that has drawn me to study solar geoengineering.

Intersectional climate activism centers the fact that climate justice and environmental, social, and racial justice are deeply intertwined. Intersectionality refers to the compounding effects of social identities on the experiences of individuals and groups. Inequalities directly tied to racism, for example, overwhelmingly put communities of color at the highest risk from environmental hazards: racial redlining of cities in the United States has historically forced Black Americans to live in neighborhoods burdened with higher levels of air and water pollution than in predominantly white neighborhoods. The growing impacts of climate change ― extreme heat, intensified storms and flooding ― also disproportionately affect these neighborhoods, deepening racial inequality. 

Since Hurricane Laura, a storm intensified by warmer sea surface temperatures, struck the southeast US last week, people living near industrial factories in Louisiana ― predominantly low-income, minority residents ― have suffered high exposure to toxic chemicals from the damage. In California, minimum-wage migrant farm workers labor tirelessly through heavy wildfire smoke and extreme heat, risking their health in order to make ends meet while facing additional risks from COVID-19. Racial disparities and lasting repercussions of colonialism similarly exacerbate the adverse impacts of climate change on marginalized communities worldwide. 

Those experiencing the most devastating and immediate impacts of the climate crisis are least responsible for its causes: per-capita emissions are much higher for the rich, and climate resilience also depends largely on wealth. Communities severely imperiled by climate change ― Pacific Island nations disappearing under rising seas, farmers forced to migrate due to crop failure, Indigenous Arctic communities losing homelands as sea ice melts away ― lack resources to cope with direct threats to their livelihoods, while wealthy consumers can simply buy their way out of experiencing the consequences of climate change, often amassing huge carbon footprints with impunity. 

Dismantling power structures that have willfully rendered droves of the population profoundly vulnerable through the violent extraction of land, resources and labor is as urgent as confronting the atmospheric drivers of climate change. Addressing environmental racism and colonialism demands reparative justice for populations long burdened by inequality: for example, returning stolen land to Indigenous communities and issuing monetary compensation to descendants of slaves for generations of unpaid forced labor.

Solar geoengineering would not correct the injustices driving unequal impacts of climate change. However, it could directly address the rising global temperatures drastically intensifying disparity.

In fact, SRM is the only known strategy that could limit global temperature rise this century.

By reflecting sunlight, SRM has the unique capacity to cool global temperatures within 1-2 years of deployment. Comparatively, even if greenhouse gas emissions cease today, accumulated atmospheric carbon dioxide (CO2) will persist for at least several centuries, continuing to warm the climate. Without SRM, limiting future global temperature rise depends heavily on negative emissions to remove excess CO2.   

Meanwhile, warmer temperatures are seriously compromising the efficacy and permanence of natural CO2 sinks, while threatening reservoirs like melting Arctic permafrost to release massive amounts of stored carbon. Reducing CO2 concentrations by even a small fraction of their excess this century requires miraculous technological breakthroughs yet to be seen in artificial carbon capture: current technologies remain very early-stage and high in energy use, land use, and cost. Even if CO2 concentrations rapidly decrease, thermal inertia of significantly warmed oceans will keep Earth warmer for a while.

Critically, SRM could ameliorate catastrophic climate damages while slower-acting mitigation takes effect. Though much remains unknown about potential risks of SRM, when compared against continued warming ― and potentially soon crossing irreversible climate tipping points ― the relative risks may be small.

The risk that solar geoengineering unintentionally causes harm (for example, by inducing unexpected and potentially destructive changes to regional climates) presents a serious moral hazard. However, a future without SRM may carry substantially higher risks and uncertainties than with SRM, particularly for climate-vulnerable communities. Research is also essential for identifying, understanding, and addressing as-yet unknown risks. Delaying or dismissing research eliminates any possibility that a well-informed SRM implementation could significantly reduce harm by limiting warming sooner than would otherwise be achievable. 

Nevertheless, climate-denying chemtrail conspiracy theorists and well-respected environmental activists denounce SRM research as a malicious plot to control the climate and weather for the benefit of specific interests. In the latter case, concerns about power and interest are absolutely warranted: ethical international governance and decision-making ― regarding research as well as implementation ― demands that distribution of resources and political power favor vulnerable and developing nations. This calls for thoughtful and inclusive discourse on restructuring global power dynamics to create radically equitable international governance systems ― a key priority in the social and political science spheres of interdisciplinary SRM research.

Concerns about detracting from greenhouse-gas mitigation efforts have also understandably turned many environmental advocates away from discussing or supporting the study of SRM. The concept of studying or investing in climate change adaptation used to draw concern for the same reasons; now, adaptation strategies are acknowledged as essential for saving lives and managing risk in the face of an overwhelming crisis.  

SRM research may sound reckless and crazy; the stakes are indeed soberingly high. But committing to the dangers of unchecked temperature rise may be even crazier. In the work toward intersectional climate justice, SRM research is increasingly urgent: a portfolio of climate risk management strategies combining mitigation, adaptation, and solar geoengineering may be our most effective ― and only ― shot at abating some of the most threatening and unjust impacts of climate change before it’s too late.

Marissa is a research fellow in the Keith group studying the effects of marine cloud brightening on regional weather and climate. She graduated from Harvard College ’19 with a degree in environmental engineering and a secondary in environmental policy and plans to pursue a PhD in climate and atmospheric sciences.