The warmistas, generally speaking, populate the U.N.’s IPCC (Intergovernmental Panel on Climate Change) and subscribe to its conclusion that most of the temperature increase of the last century is due to carbon-dioxide emissions produced by the use of fossil fuels. At any rate, this is the conclusion of the most recent IPCC report, the fourth in a series, published in 2007. Since I am an Expert Reviewer of IPCC, I’ve had an opportunity to review part of the 5th Assessment Report, due in 2013. Without revealing deep secrets, I can say that the AR5 uses essentially the same argument and evidence as AR4 — so let me discuss this “evidence” in some detail.

 IPCC-AR4 uses only the global surface temperature (GST) record. It exhibits a rapid rise in 1910-1940, a slight decline in 1940-1975, a sharp “jump” around 1976-77 — and then a steady increase up to 2000 (except for the temperature “spike” of the 1998 Super-El Niño). No increase is seen after about 2001.

 Most everyone seems to agree that this earlier increase (1910-1940) is caused by natural forces whose nature the IPCC does not specify. Clearly, the decline of 1940-1975 does not fit the picture of an increasing level of carbon dioxide, nor do the “jump” and “spike.” So the IPCC uses the increase between 1978 and 2000 as evidence for human (anthropogenic) global warming (AGW).

 Their argument is somewhat strained, and their evidence is questionable. They claim that their models simulating the temperature history of the 20th century show no warming between 1970 and 2000 — when they omit the warming effect of the steady, slow CO2 increase. But once they add the CO2 increase into the models, they claim good agreement with the reported global surface temperature record. Ergo evidence for AGW.

 There are three things wrong with the IPCC argument. It depends very much on detailed and somewhat arbitrary choices of model inputs — e.g., the properties and effects of atmospheric aerosols, and their temporal and geographic distribution. It also makes arbitrary assumptions about clouds and water vapor, which produce the most important greenhouse forcings. One might therefore say that the IPCC’s evidence is nothing more than an exercise in curve-fitting. According to physicist Freeman Dyson, the famous mathematician John von Neumann stated: “Give me four adjustable parameters and I can fit an elephant. Give me one more, and I can make his trunk wiggle.”

 The second question: can the IPCC fit other climate records of importance besides the reported global surface record? For example, can they fit northern and southern hemisphere temperatures using the same assumptions in their models about aerosols, clouds, and water vapor? Can they fit the atmospheric temperature record as obtained from satellites, and also from radiosondes carried in weather balloons? The IPCC report does not show such results, and one therefore suspects that their curve-fitting exercise may not work, except with the global surface record.

 The third problem may be the most important and likely also the most contested one. But first let me parse the IPCC conclusion, which depends crucially on the reported global surface warming between 1978 and 2000. As stated in their Summary for Policymakers (IPCC-AR4, vol 1, page 10): “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”

 But what if there is little to no warming between 1978 and 2000? What if the data from thousands of poorly distributed weather stations do not represent a true global warming? The atmospheric temperature record between 1978 and 2000 (both from satellites and, independently, from radiosondes) doesn’t show a warming. Neither does the ocean. And even the so-called proxy record — from tree rings, ice cores, ocean sediments, corals, stalagmites, etc. — shows mostly no warming during the same period.

Source

S. Fred Singer is professor emeritus at the University of Virginia and director of the Science & Environmental Policy Project, specializing in climate science and energy policy.  An expert in remote sensing and satellites, he served as the founding director of the US Weather Satellite Service and, more recently, as vice chair of the US National Advisory Committeeon Oceans & Atmosphere.  He is a senior fellow of the Heartland Institute and of the Independent Institute.  In 2007, he founded and chaired NIPCC (Nongovernmental International Panel on Climate Change).

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