WHEN the history of the global warming scare comes to be written, a chapter should be devoted to the way the message had to be altered to keep the show on the road. Global warming became climate change so as to be able to take the blame for cold spells and wet seasons as well as hot days. Then, to keep its options open, the movement began to talk about "extreme weather".
Part of the problem was that some time towards the end of the first decade of the 21st century it became clear that the Earth's average temperature just was not consistently rising any more, however many "adjustments" were made to the thermometer records, let alone rising anything like as rapidly as all the models demanded.
So those who made their living from alarm, and by then there were lots, switched tactics and began to jump on any unusual weather event, whether it was a storm, a drought, a blizzard or a flood, and blame it on man-made carbon dioxide emissions. This proved a rewarding tactic, because people - egged on by journalists - have an inexhaustible appetite for believing in the vindictiveness of the weather gods. The fossil fuel industry was inserted in the place of Zeus as the scapegoat of choice. (Scientists are the priests.)
The fact that people have short memories about weather events is what enables this game to be played. The long Australian drought of 2001-7, the Brisbane floods of 2009-10 and the angry summer of 2012-13 stand out in people's minds. People are reluctant to put them down to chance. Even here in mild England, people are always saying "I have never known it so cold/hot/mild/windy/wet/dry/ changeable as it is this year". One Christmas I noticed the seasons had been pretty average all year, neither too dry nor too wet nor too cold nor too warm. "I have never known it so average," I said to somebody. I got a baffled look. Nobody ever calls the weather normal.
So it is deeply refreshing to read the new book called Taxing Air: Facts and Fallacies About Climate Change by the internationally respected geologist Bob Carter and illustrated by the cartoonist John Spooner, which puts climate change exactly where it should be - in perspective. After demolishing many other arguments for carbon taxes and climate alarm, Carter runs through recent weather events, showing that there is nothing exceptional, let alone unprecedented, about recent droughts, floods, heat waves, cyclones or changes to the Great Barrier Reef.
How come then that last week the World Meteorological Organisation produced a breathless report claiming that "the decadal rate of increase (of world temperature) between 1991-2000 and 2001-2010 was unprecedented"? It took professor Ed Hawkins of Reading University a short time to point out that this was no longer true if you compared 1993-2002 and 2003-2012 - ie, if you took the most up-to-date records. In that case, the latest decade showed a smaller increase over the preceding decade than either of the preceding decades did. In other words, the temperature standstill of the past 16 years has begun to show up in the decade-by-decade data.
And this is even before you take into account the exaggeration that seemed to contaminate the surface temperature records in the latter part of the 20th century - because of urbanisation, selective closure of weather stations and unexplained "adjustments". Two Greek scientists recently calculated that for 67 per cent of 181 globally distributed weather stations they examined, adjustments had raised the temperature trend, so they almost halved their estimate of the actual warming that happened in the later 20th century.
Anyway, by "unprecedented", the WMO meant since 1850, which is a micro-second of history to a paleo-climatologist like Carter. He takes a long-term perspective, pointing out that the world has been warming since 17,000 years ago, cooling since 8000 years ago, cooling since 2000 years ago, warming since 1850 and is little changed since 1997. Consequently, "the answer to the question 'is global warming occurring' depends fundamentally on the length of the piece of climate string that you wish to consider". He goes on: "Is today's temperature unusually warm? No - and no ifs or buts."
Carter is a courageous man, because within academia those who do not accept that climate change is dangerous are often bullied.
Indeed, Carter, who retired from James Cook University before he got interested in the global warming debate but remains an emeritus fellow, recently found himself deprived of even an email address by colleagues resentful of his failure to toe the line. As the old joke goes: what's the opposite of diversity? University.
Viscount Matt Ridley, an acclaimed author and former Science and Technology Editor for the Economist blogs at www.rationaloptimist.com.