A new paper in The European Physical Journal by veteran MIT meteorologist Richard Lindzen gently but clearly ridicules the idea that CO2 is the control knob of the global climate system. He lays out the basic numbers and shows that even a doubling of CO2 in the atmosphere would only change total radiative absorption and emission by about 2%, which is minuscule compared to variations in cloud coverage and ocean-atmosphere interactions. He then goes through an example of how over-simplified reasoning about the role of CO2 leads to wrong conclusions when applied to other problems in climate analysis, such as explaining why the tropical climate stays so constant through long ice age cycles. Unfortunately the oversimplification tends to confirm the biased assumption, leading to circular self-reinforcing logic.
Lindzen's essay is somewhat technical. But it’s worth braving the complexities because, in addition to offering a lucid explanation of why the climate system is so complex and difficult to predict, he also offers some candid reminiscences about the history of the climate field. (And yes, he is a “climate scientist.”) Up to the late 1980s most of his senior colleagues were skeptical about the role of CO2. He lists the names of some esteemed scientists who shared his doubts about the idea that CO2 controls climate, many of whom headed important research institutes, but who are now retired or, in some cases, deceased though Lindzen, fortunately, is still going strong at age 80.
Well, isn’t it just proof that the field has changed and younger, more mentally flexible researchers are challenging old theories? Alas it is not. Instead it’s proof of the dangers of politicizing science and science funding that Eisenhower warned of in 1961, saying: “The prospect of domination of the nation's scholars by Federal employment, project allocations, and the power of money is ever present -- and is gravely to be regarded.”
As Lindzen notes, the large number of scientists attracted to the climate field after the 1980s came in pursuit of the ample grant money available to those who blamed humans for creating a crisis. That change in funding has changed the science, but not for the better. Focusing so much attention on the role of CO2, and in particular making it so lucrative to find a dominant role for CO2 especially if it’s man-made (though if humans weren’t around, blaming burning coal for a mass extinction will do), has meant efforts to understand ways the climate system can vary naturally have fallen by the wayside, with the unfortunate result that many important research topics simply haven't progressed.