Is Global Food at Risk Due to Climate Intervention? — Concerns Over Declining Protein Levels: Altering the Climate Could Change Our Dining Tables

Intervention to "Cool" the Earth Poses "Slimming" Risk to Food

According to a recent study reported by Phys.org on November 8 (U.S. time), a prominent proposal for climate intervention that reflects a portion of sunlight back into space, known as Stratospheric Aerosol Injection (SAI), may lower the protein content in the world's staple crops. The study focused on four crops: corn, rice, wheat, and soybeans. The research team combined climate and crop models to evaluate the nutritional side effects. Phys.org

What Happens: "Decoupling" of CO₂ and Temperature

The key point is that the relationship between CO₂ and temperature is decoupled by SAI. In the model, while rising CO₂ concentrations decrease protein concentration in all four crops, temperature increases tend to raise protein concentration. Since SAI cools the Earth, this "temperature offset" no longer works, leading to a relative decrease in protein. Lead author Brendan Clark emphasizes that SAI is not a "cure-all" that completely negates the effects of climate change. Phys.org

Scenarios and Methods: ARISE-SAI-1.5×CLMcrop

The study used a representative numerical experiment called ARISE-SAI-1.5 (controlled injection to maintain "effective 1.5°C" under SSP2-4.5) to map protein changes at the national level from 2060 to 2069 using **CLM (CLMcrop)**. ARISE-SAI-1.5 is designed to inject SO₂ into the stratosphere (about 21.5 km) across four latitude bands starting in 2035, maintaining the temperature around 1.5°C using a control algorithm. Phys.orgcesm.ucar.edu

Who is Most Affected: Regional Inequality and Fairness

The extent of reduction varies greatly by region, with countries suffering from severe malnutrition or protein deficiency potentially facing greater impacts. This is due to regional differences in changes in temperature, solar radiation, precipitation, and atmospheric chemistry. The authors urge that expanding local experiments and improving models should be prerequisites for policy decisions. EurekAlert!

"Yield" and "Nutrition" Are Different—Consistency with Existing Knowledge

While previous studies have shown that the impact of SAI on yield varies by crop and region, with "winners and losers" (Nature Food 2023), the evaluation of **nutrition (quality)** has been delayed. This study highlights the new possibility that quantity may increase but quality may decrease. Recent studies examining the behavior of corn production under SAI (Earth’s Future 2025) also reveal the complex interplay of interests depending on crop models and assumptions. The conclusion cannot be simplified—hence the need for a comprehensive "risk vs. benefit" assessment. ScienceDaily

Implications for the Table and Field: How to Protect Protein "Density"?

• Breeding and Variety Selection: Utilize genetic variability in protein content and consider quality indicators (essential amino acid profiles).

• Fertilization and Soil Management: Improve nitrogen use efficiency (NUE) and address the "dilution effect" (increased carbohydrates due to CO₂ increase, leading to a relative decrease in protein percentage).

• Crop Shifts: By increasing the proportion of legumes in combination with field and rice crops, complement the overall protein supply in the diet.

• Supply Chain: The decline in raw protein percentage affects feed and processing. Quality standards and pricing need to be readjusted. Unlike yield, nutrition is a less visible KPI but emerges at the intersection of international trade and nutrition policy. SpringerLink

Limitations and Future Directions

This study relies on models and does not fully incorporate regional differences in micronutrients and amino acid composition or farmers' adaptive behaviors (fertilization, varieties, sowing periods). As the authors state, **expanding field experiments and "multi-model comparisons"** are key. In the policy arena, governance (who, when, how much to inject), transboundary impacts, and consensus-building processes are questioned. EurekAlert!

SNS Reactions Picked Up

• Alan Robock (Co-author)
  "Stratospheric aerosol climate intervention could lower crop nutritional value—published in ERL"
  (announced with the study's DOI) X (formerly Twitter)

• Geoengineering Info (Commentary Account)
  "Under SAI maintaining 1.5°C, protein in corn and rice decreases, while wheat and soybeans are less affected—significant regional differences" X (formerly Twitter)

• University and Public Relations
  Rutgers' faculty news and EurekAlert! also summarized the key point as **"regions with severe malnutrition may be more affected"** and distributed it. SEBS NJAES News

※On social media, there are voices viewing SAI as a "panacea" and others warning that the "side effects are too great." The results of this study highlight the need to include nutrition as a score in policy decisions, not just yield.

Positioning of the Study (Supplementary)

• Primary Report: Phys.org (November 8, 2025). Provided by Rutgers, explanation of the study published in the peer-reviewed journal Environmental Research Letters. Phys.org

• Original Paper: Clark et al. "Stratospheric aerosol climate intervention could reduce crop nutritional value" (ERL, 2025, DOI:10.1088/1748-9326/ae1151).

• Background of Experimental Design: ARISE-SAI plan (NCAR/CESM) and the specifications of its 1.5°C control scenario.  cesm.ucar.edu
  
  

Conclusion

Mitigating global warming is essential for humans and ecosystems, but **"how to mitigate it"** can change the quality of food. If protein density decreases as a cost of cooling, it will impact nutrition policies, especially in vulnerable regions. If discussing climate intervention, nutrition should be a KPI, not just yield—this is the reality that this study presents. Phys.org+1