Research indicates that an abrupt halt to solar geoengineering may lead to a “termination shock,” causing a rapid temperature rise that could make the initiative more expensive than continuing without intervention.

With greenhouse gas emissions on the rise, there’s increasing attention on solar radiation management (SRM), which cools the planet by dispersing sulfur dioxide aerosols into the stratosphere to reflect sunlight.

However, sustained solar geoengineering is crucial for centuries; otherwise, the hidden warming could quickly reemerge. This rebound, referred to as termination shock, leaves little time for adaptation and could catalyze critical climate events such as ice sheet collapses.

According to Francisco Estrada, researchers from the National Autonomous University of Mexico assessed the risk of inaction on climate change compared to solar geoengineering approaches.

Projections suggest that if emissions aren’t curtailed, temperatures may soar by an average of 4.5 degrees Celsius above pre-industrial levels by 2100, leading to approximately $868 billion in economic damages. In contrast, a hypothetical stratospheric aerosol injection program initiated in 2020 could limit warming to around 2.8°C, potentially reducing these costs by half.

Nevertheless, if the aerosol program ends abruptly in 2030, resulting in a temperature rebound of 0.6 degrees Celsius over eight years, economic damages could surpass $1 trillion by century’s end. While estimations vary, Estrada states, “The principle remains consistent: the termination shock will be significantly worse than inaction.”

Estrada’s research innovatively gauges damage not only by global warming levels but also by the speed at which temperatures rise, according to Gernot Wagner from Columbia University.

Wagner warns that solar geoengineering may be riskier than it appears. “This highlights a critical concern,” he notes.

Make Sunsets, a Silicon Valley startup, has already launched over 200 sulfur dioxide-filled balloons into the stratosphere and offers emission offsets for sale. A recent launch in Mexico prompted governmental threats to ban geoengineering activities.

Israel’s Stardust Co., Ltd. has secured $75 million in funding and is lobbying the U.S. government to explore solar geoengineering options. A recent survey revealed that two-thirds of scientists anticipate large-scale SRM could occur this century, as reported by New Scientist.

According to studies, it would take at least 100 aircraft to cool the Earth by 1°C through aerosol injection, releasing millions of tons of sulfur dioxide annually, unimpeded by geopolitical conflicts or unforeseen events.

Presently, major nations like the United States are undermining global climate cooperation, but researchers highlight that such collaboration is essential to prevent termination shock and potentially realize the benefits of SRM.

Analysis of varying parameters suggests that aerosol injections could mitigate climate damage only if the annual probability of cessation is extremely low. In scenarios allowing for a gradual stop over 15 years, SRM might be viable.

If countries successfully reduce emissions, only minimal geoengineering cooling may be necessary, rendering aerosol injection beneficial with a maximum outage probability of 10%. This indicates a potential 99.9% chance of failure over a century, but manageable temperature recovery remains plausible in low emissions scenarios.

This need for international cooperation reveals what Estrada describes as the “governance paradox” of solar geoengineering: “We must ensure extremely low failure rates and possess effective governance to mitigate adverse outcomes.” However, he adds, “If we effectively reduce greenhouse gases, the need for SRM diminishes.”

These findings challenge the notion that solar geoengineering might lead to irresponsible development, as some have suggested, according to Chad Baum from Aarhus University. Funding for this new research was provided by the Degrees Initiative, aimed at supporting geoengineering studies in vulnerable low-income nations.

Baum stated, “We intend to complete all stages of this study, incorporating feedback from impacted communities.”

Despite this, Wagner emphasizes the imperative for further exploration into geoengineering’s trade-offs given the rise in emissions and their consequences: “We are approaching a critical juncture.”