Forecasting for disaster

If we do want to properly test these forecasting systems by seeing how well they did against results unknown at the time the forecast was made, we immediately strike the problem in that there is no agreed way of judging the result, particular as the criteria should really have been set out at the time the forecasts were made. This problem is made more acute by the fact that the time between the earliest forecasts and now is still comparatively short, for a climate system, and quite small variations in the measurements can make the difference between the forecast being below the bottom of the forecast range or well inside the forecast band.

One useful exercise is to compare the earliest IPCC forecast, issued in 1990 or 22 years ago, with what has happened since. This report, which can be found on the IPCC website says "Based on current models, we predict: under [BAU – business as usual] an increase of global mean temperature during the [21st] century of about 0.3 ^oC per decade (with an uncertainty range of 0.2 to 0.5 ^oC per decade)."

That is a little ambiguous but a graph in the report makes it clear that they mean a minimum of 0.2 degrees centigrade a decade. Over 22 years that should mean a touch over 0.4 degrees. The best increase activists can come up with in that time, using the temperature records compiled by the Goddard Institute of Space Science, known to give higher readings than the other temperature records, is somewhere short of 0.35 degrees, the bulk of which occurred in the decade following the forecast. This could be declared wrong or within measurement error of the bottom end of the forecast range or, the preferred explanation, that other factors held back measured temperatures in the past decade or so, and 20 years is too short a time to judge the forecast. Also, note that the link between CO2 and temperature cannot be holding for the past 13 years or, despite Dr Muller's analysis as temperatures have not done anything.

These arguments are endless, pointless and all the fault of the IPCC, as at no stage have any of the scientists involved with that panel understand that they are dealing with forecasting systems, rather than matters of science as such.

Governments could have conducted their own review by appointing independent committees comprised of, say, statisticians and forecasters, to compare greenhouse forecasts with actual results, including forecasts for changes in snowfall and rainfall patterns, and seasonal forecast. Instead, where governments have instituted some sort of inquiry, that inquiry has simply taken the word of the scientists involved.

None of this is to say that the climate forecasts are actually wrong as such, but merely to point out that they have not been properly verified. In particular, it is difficult to think of any reason at all to trust either the emissions forecasting or the greenhouse gas concentration scenarios. The first of these date only from 2001 (earlier estimates were straight guesses), and consist of a wide range of scenarios that are supposed to be equally likely. All that we can really say is that give the recent history of greenhouse gas concentrations the most extreme scenarios (the only ones often quoted) seem unlikely.

To persist with the carbon tax when the justification for curbing emissions is based on methodology that can only be described as badly flawed, and when it is clear no concerted international effort to curb emissions is going to occur in the foreseeable future, makes no sense of any kind.