"Forecasting is difficult: particularly about the future" This piece of wisdom is attributed to Yogi Bear. But it does not apply to the Intergovernmental Panel on Climate Change, since they do not make "forecasts" at all, only "projections". As they make clear, "projections" are dependent on the correctness of the assumptions made by the computer models and the futures scenarios from which they are made.
This has not always been so. In the first IPCC Report (1990). on the first page of the "Executive Summary" there was nearly a whole page headed " Based on current model results, we predict" with no less than ten actual "predictions".They used the phrase "models predict" several times throughout, but they did, at least admit that there were "uncertainties".
Chapter 4 was entitled "Validation of Climate Models". Paragraph 4,12 "Methods and Problems of Model Validation" showed that such validation is quite a problem, and it seemed to show that, so far, no model has been truly validated. Chapter 8 "Detection of the Greenhouse Effect in the Observations" had the answer when it said (paragraph 8.4) "the fact that we have not yet detected the enhanced greenhouse effect leads to the question: when is this likely to occur"
The next Report (1995) had, in its first draft, another Chapter 4 "Validation of Climate Models". I commented (with, perhaps, others), that since no model had ever been validated, according to their own opinions, the title was inappropriate. So in the next draft they changed the word "validation" to "evaluation" no less that fifty times, and that report and all subsequent ones have not used the terms "predict", "forecast", or "validate". Also there has been no further discussion on how validation might be made. This is true of all of the four parts of the Fourth Report.
I frequently quote this example from their "Frequently Asked Question 1.2":
"A common confusion between weather and climate arises when scientists are asked how they can predict climate 50 years from now when they cannot predict the weather a few weeks from now. The chaotic nature of weather makes it unpredictable beyond a few days. Projecting changes in climate (i.e., long-term average weather) due to changes in atmospheric composition or other factors is a very different and much more manageable issue".
Note that they insist that all they do is "project". They are admitting that "scientists cannot "predict climate 50 years from now". No wonder there is "A common confusion", The claim that their "projections" are "very different" and "much more manageable" does not include a claim that they can provide successful predictions.
And yet, the politicians, activists and many ordinary people seem to be under the delusion that the IPCC "projections" actually can be regarded as "forecasts" to the extent of promoting all manner of economically damaging measures in the belief of countering them. The above statement seems also to agree that the only scientists capable of actually predicting are the weather forecasters and it might be worth while to examine how this has been achieved, however imperfect it may seem.
Despite all this, the public, the media and the politicians seem to think that the IPCC "projections" are "forecasts" even when the IPCC denies it. It is therefore useful to see whether these projections show any success as forecasts.
The following table shows a comparison between the "projections" of the IPCC and the observed figures, extrapolated to 2010 from the latest available information. It shows that the IPCC are within range of prediction for population, coal production, CO2 emissions and CO2 concentrations, but they are completely wrong on methane concentrations, global temperature change and sea level change. It might be mentioned that the "projections" for global GDP are also all wrong, but I have been unable to find figures that make adequate allowance for the changes in the US dollar.
Cheers
Vincent Gray Wellington, New Zealand
"To kill an error is as good a service as, and sometimes better than, the establishing of a new truth or fact"
Charles Darwin
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