Appendix S1. Definitions of Acronyms.

Appendix S2. Definitions of Variables and Parameters.

Appendix S3. Summary of Expert Elicitation Results.

Appendix S4. Description of Inapplicability of Other Elicitation Data.

Appendix S5. Description of Cost of Abatement in DICE.

Appendix S6. Representative Marginal Abatement Cost Curves.

Appendix S7. Pivot Parameter Values for Individual Technology Projects.

Appendix S8. Proofs of Analytical Results.

Appendix S9. Reduced Form R&D Model.

Appendix S10. Returns Functions for the Solar-Nuclear Technology Category.

Appendix S11. Representation of Stochastic Returns Functions.

Appendix S12. Description of the Solution Procedure.

Appendix S13. Allocation of Total Investment under Different Optimal Investment Values.

Appendix S14. R&D and Riskiness of Outcomes.

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