Research or Not? Classifying Solar Radiation Modification Experiments

Overview

Objectives

By participating fully in this activity, students will learn how to:

• Explain why the word “experiment” became contested after the Make Sunsets balloon releases in Mexico and the Mexican government’s announced ban on SRM experiments
• Distinguish SRM research experiments, whose main aim is to resolve uncertainties and build generalizable knowledge, from SRM non-research experiments, whose main aim is to cool the Earth’s surface
• Classify SRM activities as research or non-research experiments from their stated aims, titles, or protocols
• Describe how plausible SRM field experiments differ in scale, technical characteristics, and governance needs
• Keep identifying an activity separate from judging whether it is responsible, and reconstruct the arguments for and against a non-use agreement on solar geoengineering

Grade Level

Needs review: The draft suggests undergraduate and graduate students, since he plans to use these materials at the University of Buenos Aires; confirm.

Undergraduate, Graduate

Standards

• HS-ETS1-3 — Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics, as well as possible social, cultural, and environmental impacts.
• HS-ESS3-4 — Evaluate or refine a technological solution that reduces impacts of human activities on natural systems.

United Nations Sustainable Development Goals

• SDG 13 — Climate Action: Take urgent action to combat climate change and its impacts
• SDG 16 — Peace, Justice and Strong Institutions: Promote peaceful and inclusive societies for sustainable development, provide access to justice for all and build effective, accountable and inclusive institutions at all levels

Materials Required

• The SRM360 perspective “‘Make Sunsets’ in Mexico: Lessons for SRM Governance” (Daly, Mastroleo, and Carabajal, 2025)
• Redmond Roche et al. (2026), “Differentiating Solar Radiation Modification Field Experiments,” for the case descriptions
• The non-use agreement proposal (Biermann et al., 2022) and the response by Parson et al. (2024), in English or in Spanish translation
• Optional: introductory videos in Spanish by Inés Camilloni and colleagues
• Paper and pencil

Learning Sequence

Lesson Plan Introduction

Debates about solar radiation modification often run together very different activities, from small scientific field tests to commercial balloon releases to deployment. This lesson, based on the work of Ignacio Mastroleo, Timothy Daly, and María Inés Carabajal, asks students to identify an activity first and evaluate it second, as research ethics does for clinical trials and the compassionate use of experimental drugs.

Activity Details

1. The Make Sunsets Case

• Introduce the case: in April 2023 the for-profit startup Make Sunsets released small balloons carrying sulfur dioxide in Baja California, Mexico, without engaging Mexican authorities, as part of selling “cooling credits.” The Mexican government then announced its intention to ban all forms of SRM experiments, including research.
• Students read the SRM360 perspective “‘Make Sunsets’ in Mexico: Lessons for SRM Governance.”
• Discussion question: Should one company’s actions lead to a ban on all SRM research? What would be lost, and what would be protected?

2. Defining an SRM Experiment

• Present Daly, Mastroleo, and Carabajal’s definition of an SRM experiment: “a deliberate use of an SRM intervention at any scale, with either a research or non-research main aim, and without sufficient evidence of safety and/or efficacy for its regular use in the Earth system.”
• Distinguish SRM research experiments, whose main aim is to resolve uncertainties about the use or non-use of SRM and build generalizable knowledge, from SRM non-research experiments, including deployment, whose main aim is to cool the Earth’s surface to address climate impacts.
• Compare the two examples: Make Sunsets as a small-scale non-research experiment, and SCoPEx, which aimed to “advance understanding of the risks and efficacy of SRM,” as a research experiment.

3. Classifying Cases

• Give groups a set of cases, each described only by its title or stated aim and protocol, for example Make Sunsets’ balloon releases, SCoPEx, and plausible field experiments described by Redmond Roche et al. (2026), such as a microphysical process balloon experiment, a sea salt particle generation and lofting experiment, and a sustained multi-plume marine cloud brightening experiment.
• Each group classifies every case as a research or non-research experiment and records the evidence it used.
• Discussion question: Which cases were hard to classify, and what information would have settled them?

4. Scale and Governance

• Present Redmond Roche et al.’s finer-grained typology of plausible research experiments for stratospheric aerosol injection, marine cloud brightening, and cirrus and mixed-phase cloud thinning, and their near-, intermediate-, and distant-phase categories.
• Discuss why a simple “small-scale versus large-scale” distinction is not enough for governance.
• Discussion question: Should a small research experiment and a small commercial release be governed by the same rules? Why or why not?

5. Arguments For and Against a Non-Use Agreement

• Keep evaluation as a separate step: students have identified the activities; now they weigh whether they are responsible.
• Groups reconstruct the main arguments of the proposed international non-use agreement on solar geoengineering (Biermann et al., 2022) and of the response by Parson et al. (2024). Spanish translations of both are available.
• Discussion question: Does the non-use agreement distinguish research from deployment? How would the classification from this lesson change the debate?

Conclusion

Close with a values-based question: Why does it matter to identify what kind of activity is proposed before deciding whether it is acceptable, and who should make that decision?

Lesson materials

Download the files below to teach this lesson. PDFs are accessible versions; PowerPoint and Excel files can be edited for your class.

Teacher resources

• Geoingeniería solar: ¿quién controla el termostato de la Tierra?

  Inés Camilloni's introductory TEDxRiodelaPlata talk on solar geoengineering (2022), in Spanish.

  • Watch YouTube video (Spanish): Geoingeniería solar: ¿quién controla el termostato de la Tierra?

• Cambio climático, ética, salud y geoingeniería solar

  A 2026 FLACSO Argentina bioethics seminar with four short lectures by Inés Camilloni, Fernando García Gibson, María Florencia Santi, and Ignacio Mastroleo, in Spanish.

  • Watch YouTube video (Spanish): Cambio climático, ética, salud y geoingeniería solar

• “Make Sunsets” in Mexico: Lessons for SRM Governance

  SRM360 perspective by Timothy Daly, Ignacio Mastroleo, and María Inés Carabajal (2025) that defines research and non-research experiments.

  • Open Link: “Make Sunsets” in Mexico: Lessons for SRM Governance

• Differentiating Solar Radiation Modification Field Experiments: Scale, Technical Characteristics, and Governance Implications

  Redmond Roche et al. (2026), Earth's Future, open access: the typology of plausible field experiments used for the classification cases.

  • Open Link: Differentiating Solar Radiation Modification Field Experiments: Scale, Technical Characteristics, and Governance Implications

• Solar geoengineering: The case for an international non-use agreement

  Biermann et al. (2022), WIREs Climate Change. Spanish translation by Gian Franco Lisanti and Julieta Nasi (2026), CC BY 4.0, from Zenodo (doi:10.5281/zenodo.22047789).

  • Open Link: Solar geoengineering: The case for an international non-use agreement
  • Download PDF (Spanish): Solar geoengineering: The case for an international non-use agreement

• Toward an evidence-informed, responsible, and inclusive debate on solar geoengineering: A response to the proposed non-use agreement

  Parson et al. (2024), WIREs Climate Change. Spanish translation by Ignacio Mastroleo, María Inés Carabajal, Julieta Nasi, and Gian Franco Lisanti (2026), CC BY 4.0, from Zenodo (doi:10.5281/zenodo.22047666).

  • Open Link: Toward an evidence-informed, responsible, and inclusive debate on solar geoengineering: A response to the proposed non-use agreement
  • Download PDF (Spanish): Toward an evidence-informed, responsible, and inclusive debate on solar geoengineering: A response to the proposed non-use agreement

Credit and contact