The Guardian amends letters page after numerical error in solar geoengineering debate
The Guardian has amended a published letter in its debate on solar geoengineering after correcting a significant numerical misstatement about the potential effects of solar radiation modification. A clarification appended to the piece noted that an earlier version of a letter from Professor Hugh Hunt had incorrectly stated that spraying 10 million tonnes of material into the atmosphere could achieve a cooling of 10 degrees Celsius. The corrected version makes clear that the figure referred to a cooling of 1 degree Celsius, with the error attributed to a misunderstanding during editing.
The original presentation placed the incorrect figure within a wider exchange responding to a Guardian editorial that was sceptical of geoengineering research. As printed, the claim appeared to suggest that a relatively small-scale intervention could generate an extraordinarily large climatic effect. In the context of an already polarised discussion about technological climate interventions, that figure stood out as both dramatic and destabilising, lending weight to concerns about overreach, feasibility and unintended consequences.
Correcting the figure materially changes the scale at which the argument operates. A potential cooling of 10 degrees Celsius would imply a transformative and arguably implausible intervention, likely to overshadow all other considerations about governance, risk and proportionality. A cooling of 1 degree Celsius, by contrast, aligns more closely with mainstream scientific discussions of solar radiation modification as a limited, temporary and supplementary measure rather than a wholesale solution. The amendment therefore recalibrates the reader’s understanding of both the claim itself and the broader debate in which it sits.
The correction is particularly salient given the format in which the error appeared. Letters pages are designed to host contestation and disagreement, but they also rely on a baseline of factual accuracy to allow readers to assess competing claims. In this case, the incorrect figure did not merely embellish an argument but altered its apparent magnitude. Left uncorrected, it risked distorting perceptions of what proponents of geoengineering research are actually proposing or studying.
This episode also highlights the editorial challenges of covering highly technical subjects in opinion-driven sections. Climate science, and geoengineering in particular, involves precise terminology and quantitative claims that do not easily survive compression or paraphrase. When such details are misstated, even inadvertently, they can reinforce scepticism or fear rather than inform deliberation. The Guardian’s decision to issue a clear correction acknowledges that responsibility.
More broadly, the amendment speaks to the importance of numerical precision in climate reporting. In debates where policy, ethics and global equity intersect, figures are not incidental. They shape judgments about risk, urgency and plausibility. Ensuring that those figures are accurate is essential not only for fairness to contributors but for maintaining trust in the forum as a place where complex arguments can be weighed on their merits.