¿Cuándo cambió el calentamiento de bueno a malo?

Ed Hawkins raised an interesting question on twitter today that has interested me for some time:

This led to a long twitter-spat involving Steve Mcintyre, Doug McNeall, Richard Betts and others.

In the past, warming was generally thought to be a good thing. Here are a few illustrations of this.

Arrhenius, 1904

In 1904, Arrhenius wrote that an increase in atmospheric carbon dioxide due to the burning of fossil fuels could be beneficial, making the Earth’s climates “more equable,” stimulating plant growth, and providing more food for a larger population.

Callendar, 1938

Guy Callendar ended his 1938 paper with

In conclusion it may be said that the combustion of fossil fuel, whether it be peat from the surface or oil from 10,000 feet below, is likely to prove beneficial to mankind in several ways, besides the provision of heat and power. For instance the above mentioned small increases of mean temperature would be important at the northern margin of cultivation, and the growth of favourably situated plants is directly proportional to the carbon dioxide pressure (Brown and Escombe, 1905). In any case the return of the deadly glaciers should be delayed indefinitely.

Gordon Manley, 1951

Manley is best known for establishing the Central England Temperature (CET) record. In 1944 he gave a lecture and wrote a paper, discussed here, about warming, and in 1951 wrote another paper saying that “the present improvement appears to have set in about 1925-30”.

UNESCO Report, 1963

UNESCO published a long report in 1963 on Changes of Climate, with articles published in both English and French. There are several references to “amelioration”, such as “the finding of a climatic amelioration during the previous 100-150 years” (p 8) and “recent climatic amelioration” (p 327).

Barry and Chorley, 1970

Roger Barry and Richard Chorley wrote a textbook, first published in 1968, called “Atmosphere, Weather and Climate”. New editions of it are still available. If you look at the 1970 edition on Google books, you will find on page 277 the statement that “Unfortunately the latest evidence suggests that the warm period of the 1920s and 1930s has come to an end.” You won’t find that in the latest edition of course. At some later stage, that sentence was removed.

Hubert Lamb, 1973

Here’s an article from 1973 by Hubert Lamb (scroll down to page 17) in which he talks of the warming in the early 20th century “opening up new pastures and land for cultivation” and “increasingly genial conditions”. He goes on to say that “It soon became clear, however, that carbon dioxide was not the whole story” and “For the past 25 to 30 years the Earth has been getting progressively cooler again”. Lamb was of course the founder of CRU.

So it seems that it was a truth universally acknowledged that warmer climates were beneficial, until at least the 1970s. But then something happened in the 1980s. Decades, if not centuries, of science and common sense were overthrown and replaced with the vast, self-reinforcing, political bandwagon of groupthink that we have today.