Even aggressive climate intervention strategies like SAI may fail to save our planet's coffee fields. (Credit: Alf Ribeiro on Shutterstock)
In A Nutshell
- Cooling from SAI does not reliably help wine, coffee, or cacao across most major regions; results vary widely by year and place.
- Only six of 18 regions show uniform outcomes under the stronger SAI scenario, highlighting how natural variability drives results.
- Spain’s grape growers often benefit; Cameroon’s cacao shows consistent gains. Coffee in eastern Brazil trends negative later on.
- Revenue estimates use a strict “no suitable year, no export revenue” rule, so they are upper bounds rather than forecasts.
Stratospheric aerosol injection, or SAI, seems more like science fiction than climate science. Characterized by spraying reflective particles into the upper atmosphere to cool the planet by blocking sunlight, SAI is considered one of the most controversial climate intervention strategies.
It may sound like a movie, but would SAI actually help? Research tells us only six out of 18 major wine, coffee, and cacao-producing regions would see uniform outcomes, whether positive or negative, if scientists deployed the most aggressive version of SAI. This finding underscores massive uncertainty about geoengineering’s agricultural effects.
Per research published in Environmental Research Letters, while SAI successfully reduced temperatures in computer simulations, it failed to produce consistent results for growing grapes, coffee, and cacao in most major production areas.
Researchers from Colorado State University crunched the numbers on 18 top-producing countries and states from 2036 to 2045, comparing two different SAI scenarios against a future without intervention. Previous studies looked at cereal crops like rice and wheat, but few examined luxury crops, and few considered how unpredictable year-to-year weather could scramble the results.
The Climate Lottery
Led by Ariel Morrison, the research team analyzed multiple computer simulations of possible futures. Even under identical intervention strategies, some scenarios showed dramatically better growing conditions while others got worse.
Take France, one of the world’s top wine exporters. When comparing the SAI scenario against a future without intervention, the range of potential revenue outcomes across different climate simulations spanned nearly $60 billion over a decade. That enormous spread comes from year-to-year variations in precipitation and humidity that SAI doesn’t control.
Southern Spain was one of the few bright spots. At least 80% of the climate simulations showed consistent improvement there. Cooler temperatures helped grapevines meet their chilling requirements, those cold hours needed for vines to break dormancy and produce fruit.
SAI Solves One Problem, Creates Another
SAI reduces some agricultural risks while potentially increasing others. Cooler temperatures might prevent heat stress, but shifting precipitation patterns and higher humidity can trigger disease outbreaks that devastate crops.
For coffee growers in eastern Brazil, SAI brought more rainfall in some scenarios, helping with water supply. But in later decades, the same region shifted to experiencing negative impacts under SAI, particularly under the more aggressive cooling scenario.
Brazil is the world’s largest coffee producer by exports. An extended period of poor growing conditions there would ripple through global prices, affecting coffee drinkers everywhere.
West African cacao showed similar instability. Cameroon was the only cacao region with consistently positive results under the stronger SAI scenario. Elsewhere, the risk of black pod rot disease varied wildly between different climate possibilities.
The researchers tracked whether environmental conditions stayed within acceptable ranges for each crop. For grapes, eight different factors from spring frosts to fungal diseases. Coffee faced ten threats including frost and multiple pests. Cacao battled six concerns including witches’ broom disease and frosty pod rot.
Any year where conditions fell outside acceptable ranges meant no quality harvest and zero revenue. This assumption makes the revenue calculations an upper bound on potential economic impacts.
Disease Beats Heat Stress
Where SAI actually helped wasn’t where scientists might expect. Reducing disease risk turned out to be more important than preventing heat stress in many regions.
Mildew susceptibility decreased in grape-growing areas under SAI due to cooler temperatures. For cacao in Cameroon, lower temperatures reduced disease pressure enough to improve outcomes across nearly all scenarios tested.
But humidity changes worked against farmers in other areas. Arabica coffee, more sensitive than its Robusta cousin, faces threats from rust, brown eye spot, and other diseases that thrive in specific temperature and humidity combinations. SAI altered those combinations in unpredictable ways across different regions.
Pests like the coffee berry borer beetle and leaf miner moth also showed variable responses to SAI’s climate shifts. Some scenarios created perfect conditions for pest outbreaks even as temperatures stayed cooler.
The Money at Risk
The researchers calculated potential revenue impacts based on average 2012-2022 export values. These figures only capture international sales, not domestic consumption, tourism, or jobs.
Most regions showed enormous spreads between the best and worst outcomes. Only six regions had uniform results, all showing either positive or negative outcomes across every climate simulation. And that only held true for the more aggressive intervention that aimed to keep global temperatures 1.0°C above pre-industrial levels.
Other major producers faced deep uncertainty. By the 2050s, some regions like Chile and Vietnam showed uniformly negative outcomes for grapes and coffee. France, Australia, Germany, Brazil, Colombia, Indonesia, Nigeria, Ghana, Cote d’Ivoire, and Ecuador all had mixed results.
Is SAI Worth It?
For luxury crop producers wondering if SAI might save their livelihoods, this research delivers a sobering message: climate intervention isn’t a silver bullet.
The study’s authors noted their results shouldn’t directly inform policy due to model limitations. But the findings reveal something crucial: natural climate patterns create enormous uncertainty about how SAI would affect agriculture, even where average conditions might seem favorable.
For millions of people depending on wine grapes, coffee, and cacao, that uncertainty is the story. A single bad growing year can sink a small producer. Several bad years in a row could reshape global supply chains and prices for these crops that matter to cultures and economies worldwide.
Disclaimer: This article explains one peer-reviewed study and its limits. It should not guide farming, business, or policy decisions. For specific decisions, consult the paper itself and seek expert advice.
Paper Summary
Methodology
The team used the Community Earth System Model version 2 to test two stratospheric aerosol injection setups, ARISE-SAI-1.5 and ARISE-SAI-1.0, against a no-SAI future under SSP2-4.5. Sulfur dioxide was injected at four stratospheric sites starting in 2035, with a feedback algorithm that adjusted amounts to keep global temperatures near 1.5 °C or 1.0 °C above preindustrial levels while holding large-scale temperature gradients. Model outputs were bias-adjusted against observed datasets for temperature, precipitation, and humidity. The authors then computed crop-specific agroclimatic indices: eight for grapes, ten for coffee, and six for cacao, covering heat and cold thresholds, water supply, and key diseases and pests. A composite rule marked any year as unsuitable if even one index fell outside the acceptable range. Suitable years from 2036–2045 were tallied across 10 ensemble members per SAI scenario and five for SSP2-4.5, then converted to revenue differences using average 2012–2022 export values in 2024 dollars.
Results
SAI cooled the modeled climate but did not deliver dependable benefits for most regions. Only six of the 18 areas showed uniform outcomes across all ensemble members, and that occurred only under the stronger ARISE-SAI-1.0 case. Natural variability produced large spreads in results, including a revenue range for France that reached into the tens of billions of dollars when comparing SAI to no-SAI. Southern Spain stood out with improvement in at least 80 percent of members, helped by cooler temperatures that met chilling and heat-balance needs for grapes. Coffee results in eastern Brazil were mixed, with better water supply early on, then a shift to negative responses later, particularly under ARISE-SAI-1.0. Cacao in Cameroon showed consistent gains in most simulations, driven by disease-related rainfall patterns. By the 2050s, several patterns sharpened, with California, Italy, and Spain grapes remaining positive under both SAI scenarios and Chile grapes and Vietnam coffee turning uniformly negative.
Limitations
The study focused only on macroclimate conditions and did not account for human adaptations like irrigation, disease management techniques such as pruning, or technological advances in crop varieties. The agroclimatic indices cover physiological extremes but assume all grape, coffee, and cacao varieties respond identically to environmental conditions, which oversimplifies reality.
The model resolution of approximately 1°x1° does not capture topographic effects, microclimates, or variations in sunlight under tree canopies or on hillsides that influence actual growing conditions. The researchers did not downscale the climate data to avoid introducing additional uncertainties.
Revenue calculations used only export values from 2012-2022, which don’t capture domestic sales, tourism revenue, or employment impacts. The assumption that unsuitable years produce zero revenue is an upper-bound estimate that doesn’t reflect farmers’ ability to salvage partial harvests or adjust practices mid-season. Economic projections extended only through 2065 and didn’t account for price changes, market shifts, or adaptation investments farmers might make.
The study examined only two SAI scenarios with specific temperature targets and injection strategies. Different deployment approaches, injection locations, or temperature goals could produce different agricultural outcomes. The research also didn’t assess potential direct effects of stratospheric aerosols on solar radiation reaching crops, which could affect photosynthesis independently of temperature and precipitation changes.
Natural variability was captured using 10 ensemble members for each SAI scenario and five for SSP2-4.5, which provides substantial but not comprehensive coverage of possible climate outcomes. The simulations also don’t account for potential changes to natural variability patterns under SAI deployment itself.
Funding and Disclosures
This research was supported by Quadrature Climate Foundation Grant 01-21-000338 and Founder’s Pledge award 240905. The authors declared no commercial or financial conflicts of interest. The researchers thanked B. Dobbins for providing access to unprocessed ARISE-SAI-1.0 output data and C. Connolly for comments on the economic perspective.
Publication Details
Morrison, A.L., Barnes, E.A., Hurrell, J.W., and Hueholt, D.M. (2025). “Macroclimate growing conditions for luxury crops after stratospheric aerosol injection,” published November 4, 2025 in Environmental Research Letters, 20, 114063. doi:10.1088/1748-9326/adfbff
