A government emissions estimate revised upward by a factor of 100 does not merely update a spreadsheet — it retroactively changes the basis on which policy was debated. The UK's 123 million metric ton projection for AI data center emissions through 2035 arrived in documents accompanying a Compute Roadmap, without a press conference or a formal correction notice. Campaigners who had been pressing ministers using the earlier figure now must restate every argument they made; the institutional record does not rewind with them. The practical consequence is that the UK's…