Science as System

In the current global warming debate it would be helpful to have an idea about how the science system works when trying to evaluate the widely publicized outputs. Here is a meta-model discussed today in the Principles of Environmental Science.

Science is fundamentally about developing models. Usually the models are expressed mathematically or as computer code or both. Model development, however, is just the first step. The model must be tested against reality and revised if it doesn't fit the data.

After enough independent tests, revisions and validations, a model can be generalized into a theory (a model along with all its tests and revisions). Theories, so defined, accumulate our base of knowledge (scientia).

Is this the way it always happens? Not exactly! Many models in economics and system dynamics skip from model directly to theory and received wisdom. For example, consider William Norhaus' DICE model and the Limits to Growth models. I have been unable to find anything other than casual attempts to relate the model outputs to historical data.

Another approach in the global warming debate is to present tests without either a model or a theory. The work of Bjorn Lomborg provides a notorious example. Simple historical time plots are presented to "disprove" the global warming assertion and argue that things are actually getting better.

Compared to the two approaches above, the Intergovernmental Panel on Climate Change (IPCC) is doing science. The assessment and technical reports are essentially presentations of models along with results from testing. For some technical areas, there are no models. For some other technical areas, there are few tests. For the Integrated Assessment Models used to develop the family of Emissions Scenarios, it's sometimes hard to tell the status of the models. The testing probably needs improvement. Possibly that's why the IPCC publishes scenarios rather than forecasts with probability assessments. It's an important area that needs more scientific attention.