The Broken Chair

When politicians and journalists declare that the science of global warming is settled, they show a regrettable ignorance about how science works. We were treated to another dose of it recently when the experts of the Intergovernmental Panel on Climate Change issued the Summary for Policymakers that puts the political spin on an unfinished scientific dossier on climate change due for publication in a few months’ time. They declared that most of the rise in temperatures since the mid-20th century is very likely due to man-made greenhouse gases.

The small print explains “very likely” as meaning that the experts who made the judgment felt 90% sure about it. Older readers may recall a press conference at Harwell in 1958 when Sir John Cockcroft, Britain’s top nuclear physicist, said he was 90% certain that his lads had achieved controlled nuclear fusion. It turned out that he was wrong. More positively, a 10% uncertainty in any theory is a wide open breach for any latterday Galileo or Einstein to storm through with a better idea. That is how science really works.