Complaint to Ofcom Regarding The Great Global Warming Swindle

2. Complete Transcript and Rebuttal

Page 77




Since all the models assume that man-made CO2 causes warming, one obvious way to produce a more impressive forecast is to increase the amount of imagined man-made CO2 going into the atmosphere.

[Comment 92: This statement by the narrator, combined with the accumulation of consecutive interviewee statements which taken together amount to narration, presents a highly inaccurate picture of climatology, and misrepresents the true nature of how climate modelling is undertaken.

Firstly, scientists do not know everything there is to know about the Earths climate. Particular uncertainties concern the role in climate change of the carbon cycle, ocean circulation and clouds. Thus it is quite reasonable to adjust the parameters/assumptions to see what effect doing so has on the models. This, in fact, this is a standard part of any scientific study in the form of a sensitivity analysis (see Wikipedia:

Furthermore, because the models can be used to simulate a wide variety of situations (e.g. past climate such as ice ages, and maybe even climate on other planets) they have to pass the test of modelling current (and, increasingly, past) climate reasonably accurately before they can be used to simulate the future. The models, their structure and assumptions, and their parameter values, are all selected to eliminate those giving unreasonable results, contrary to what is suggested by the narration and contributors. For a good example of how accurately climate models do in fact model the temperature of the past, see [IPCC] and [Global Warming Art].

Other studies may involve a Monte Carlo simulation of complex systems (see, with many degrees of uncertainty (like atmospheres, or industrial process chains), where the parameters are changed in order to find out how different combinations of assumptions affect the system.

For the narrator to suggest that climate model parameters are changed with the purpose of generating impressive forecasts is simply false, and such a study would not pass a cursory peer-reviewed inspection.

Secondly, in addition to the uncertainties in the climate system, another uncertainty is what level of greenhouse gas emissions will be released into the atmosphere in future. We simply do not know, because it depends on decisions that governments and individuals make in the future, which is relatively unpredictable. Because of this, climate models are not used to make forecasts (although they are often presented as such in the popular press), but instead are used to create climate scenarios, in which one says, in effect, if we assume for the sake of argument, x, y and z, in terms of population growth, economic growth, technology improvements, and so on, what would be the likely future outcomes of that in terms of atmospheric levels of CO2 and hence climate? Usually a range of such possible scenarios are provided by experts who are not climate scientists, such as economists, population and technology experts; and the climate modellers then input these scenarios into their models to see what the likely outcomes for future climate are likely to be, in each scenario.

Continued …

[Bookmarks on this page: Click the following link to go to that bookmark. You can then copy and paste the bookmarks url from your address bar, and send it to someone as a link straight to that bookmark:
Comment 92: Serious misrepresentation of how climate modelling is carried out]


Page 77 of 176

Final Revision

Last updated: 11 Jun 2007