I was not always a lukewarmer. When I first started writing about the threat of global warming more than 26 years ago, as science editor ofThe Economist, I thought it was a genuinely dangerous threat. Like, for instance, Margaret Thatcher, I accepted the predictions being made at the time that we would see warming of a third or a half a degree (Centigrade) a decade, perhaps more, and that this would have devastating consequences.
Gradually, however, I changed my mind. The failure of the atmosphere to warm anywhere near as rapidly as predicted was a big reason: there has been less than half a degree of global warming in four decades — and it has slowed down, not speeded up. Increases in malaria, refugees, heatwaves, storms, droughts and floods have not materialised to anything like the predicted extent, if at all. Sea level has risen but at a very slow rate — about a foot per century.
Also, I soon realised that all the mathematical models predicting rapid warming assume big amplifying feedbacks
in the atmosphere, mainly from water vapour; carbon dioxide is merely the primer, responsible for about a third of the predicted warming. When this penny dropped, so did my confidence in predictions of future alarm: the amplifiers are highly uncertain.