The value of information about solar geoengineering and the two-sided cost of bias

Solar geoengineering (SG) might be able to reduce climate risks if used to supplement emissions cuts and carbon removal. Yet, the wisdom of proceeding with research to reduce its uncertainties is disputed. Here, we use an integrated assessment model to estimate that the value of information that reduces uncertainty about SG efficacy. We find the value of reducing uncertainty by one-third by 2030 is around $4.5 trillion, most of which comes from reduced climate damages rather than reduced mitigation costs. Reducing uncertainty about SG efficacy is similar in value to reducing uncertainty about climate sensitivity. We analyse the cost of over-confidence about SG that causes too little emissions cuts and too much SG. Consistent with concerns about SG’s moral hazard problem, we find an over-confident bias is a serious and costly concern; but, we also find under-confidence that prematurely rules out SG can be roughly as costly. Biased judgments are costly in both directions. A coin has two sides. Our analysis quantitatively demonstrates the risk-risk trade-off around SG and reinforces the value of research that can reduce uncertainty.Key policy insights The value of reducing uncertainty about solar geoengineering is comparable to the value of reducing uncertainty about other key climate factors, such as equilibrium climate sensitivity.The benefits of research that reduces uncertainty about solar geoengineering may be more than a thousand times larger than the cost of a large-scale research programme.Under-confidence in solar geoengineering’s effectiveness can be as costly as over-confidence.The majority of the benefits of reduced uncertainty come from reducing climate damages rather than from slowing emissions reductions.