UPDATE: Thursday 11th February 18.23
Scientist for Truth has provided a link to a very powerful essay on Jerome Ravetz and PNS at:
In it he sets out clearly the philosophical background to PNS. Scientist for Truth argues that PNS has little, or nothing, to do with science, and everything to do with a political philosophy. I urge readers to read it. All the comments here have been very stimulating and I think you will enjoy this article which had slipped under my radar.
The essay posted by Jerome Ravetz over at WUWT has caused quite a stir and provoked some heated debate. For those who haven’t read it I urge you to do so. It can be found here:
It is a closely argued analysis of Climategate and a defense of it within the context of post-normal science. Ravetz argues that we can understand the current climate hysteria if we understand that the scientists were practising normal (Kuhnian) science when in fact ‘climate science’ is actually post-normal. What do we mean by these terms and how does climate science fit into the picture.
As I understand it the Kuhnian view of science is rather analagous to the punctuated equilibrium theory of evolution. We practise our science within a current paradigm and carry out experiments to falsify that paradigm. Over time observations that lie outside the explanatory power of the existing paradigm accumulate and when they reach a significant level a revolutionary phase in science occurs in which a new paradigm rapidly develops and takes over. Following this step change in understanding we are in a new period of stasis or equilibrium in which we fill out the new picture, using the scientific method and putting the bits of the jigsaw puzzle together. A good example might be Continental Drift. Whilst Wegener proposed, in the early part of the 20th century that the continents must have wandered over the planet because of the apparent fit of the continental margins most geologists still worked within the paradigm of geosynclines arguing that only vertical movements of the earth’s crust occurred rather than major horizontal movements. It was only with the discovery of magnetic stripes on the ocean floor, the mid-ocean ridges, and fault plane solutions for transform faults etc. that were inconvenient to the geosyncline view of the earth that we entered the revolutionary change in our understanding that we now know as plate tectonics. It is now inconceivable to us that any other view existed. We might also think of the earth centred and heliocentric views of the solar system, Newtonian gravity and relativity as other examples. It is important to remember that at the time a paradigm is dominant it does have explanatory and predictive properties that allow us to test it’s key tenets. When the model fails it is proven to be in error and a new paradigm is required.
We can study components of the climate system in exactly the same way, developing hypotheses and using experiment to falsify these. Our paradigms are the currently understood laws of physics. We can apply these in hypotheses and develop experiments to test these. An example is the CERN CLOUD experiment which aims to determine if galactic cosmic rays can interact with the atmosphere to produce cloud condensation nucleii. Thus climate science is essentially using physics and chemistry to understand the way the climate system works and how it responds to radiative forcing.
In this Kuhnian view of science there is no role for advocacy. We objectively question nature and seek truth.
In contrast Ravetz argues that climate science is a post normal science. He suggests that the reason for the predicaments many climate scientists find themselves in is that they have been practising Kuhnian science in a post normal science field. This is a difficult concept to fully understand. However, what Ravetz suggests to us is that Kuhnian science is exact with little understanding of probability, errors, and uncertainties. He even suggests that science students today are taught little about these concepts. In contrast he characterises post normal science as one where the facts are uncertain, the values are in dispute, the stakes high and decisions are urgently needed. Thus we see that for Ravetz climate science is predicated on the fact that the climate is warming at an alarming rate, that we have great gaps in our knowledge, and that urgent decisions must be made.
Because of the gaps in our knowledge the approach to post normal science is different to the Kuhnian approach. Ravetz suggests that there is a wide stakeholder community that should be included in peer review, the so called extended peer community. This peer community can bring their own ‘local knowledge’ or ‘extended facts’ to the debate. It strikes me that this is another way of trying to seek concensus, rather than knowledge, truth and understanding. In many ways it strikes me as another description of what Feynmann would call ‘cargo cult science’.
To me Ravetz’s analysis is deeply flawed. The only approach we can take is that of the scientific method and use our knowledge of physics and chemistry to develop plausible hypotheses which we can test. If an idea cannot be developed into a testable hypotheses it remains just an idea. The theory of CO2 induced catastrophic global warming is just that: an idea that cannot be experimentally falsified. In the absence of any direct ability to test the idea we must apply common sense or Occam’s razor. For example the principle of uniformitarianism suggests that if CO2 is the dominant forcing component in the climate system then there should be abundant evidence of temperatures scaling with CO2 levels. As a first order test we can look at the Eemian intergalcial about 125,000 years ago. During this period CO2 levels were about 280ppm (100ppm below present day levels) and temperatures several degrees warmer than present. Here we see immediately that temperature is not a simple function of atmospheric CO2 levels and we have to look at other components in the climate system to explain the Eemian climate.
Where does this leave us. I suggest that post normal science is a social construct without meaning. It fits the current zeitgeist in which humanity is vulnerable to a multiplicity of disasters: epidemics, nuclear obliteration, global warming etc. The characterization of Kuhnian, and the scientific method as having no regard for probability, error, uncertainty and only being applicable to well controlled experimental systems in the laboratory is wrong. Finally, the only way we can fully understand the climate system is by using what we all know as the scientific method.