Defined, pace Kuhn, by ([Funtowicz1993]) using a great many words that I shall roughly distil thus: Science in the domain where we can no longer access a semblance of a large ensemble of experiments upon which to test our hypotheses. This is a problem for science as such, which does best when there are many observations to statistically smooth out the imperfections in our tests so that we can to come to a description of some underlying dynamics. Or, at least, that’s what I was told in high school, measuring the slope of our stop-watch-timed weight-dropping measurements to find a value for gravity.
The prototypical example of a subject of post normal science is the Earth. We can’t extrapolate in any meaningful way from a single data point, so lots of questions pertaining to it dynamics become difficult. Since Earth is the only planet with life we know, how many others out there have life? Since this is the only industrial economy coupled to a planetary atmospheric system that we have known, how do we know if global warming will occur and mess us up royally? Must we throw up our hands in despair and fall back on rhetoric?  Pragmatically speaking, we do, and will, and trial by op-ed and placard is the engine of democracy. But ideally, methodologically, I mean, are there alternatives?
The how-much-life-in-the-galaxy thing is not intractable - for example the speed with which life arose on our planet gives hints to the ease of life formation - Bayesians love that kind of thing. ([Spiegel2011]).
|||e.g. 5 points to ([Ravetz2003]) for arguing that climate change models are a Baudrillardian seduction.|
|[Funtowicz1993]||Funtowicz SO, Ravetz JR, 1993. Science for the post-normal age. Futures. Online.|
|[Ravetz2003]||Ravetz JR, 2003. Models as Metaphors: A New Look at Science. Public Participation in Sustainability Science: A Handbook. Online.|
|[Spiegel2011]||Spiegel DS, Turner EL, 2011. Life might be rare despite its early emergence on Earth: a Bayesian analysis of the probability of abiogenesis. eprint arXiv:1107.3835. Online.|