AFAIK, the science behind climate change is as credible as the science behind evolution or the big bang.
This isn’t true. (Actually I’m not 100% sure of the status of the big bang. I was under the impression that the book is not closed on it yet, but it’s not like I’m up to date on the field or anything).
The difference between economics and climatology/physics/chemistry/geology/biology etc... is that economics is dependent purely on the actions and psychology of humans and is more akin to sociology than hard science. It is entirely possible the societies could exist where nearly every rule of economics as we understand it could be turned on its head (CF Native Americans), the same is not true of climatology. No human belief system can change the fact that water evaporates at a certain temperature or that plants absorb x-amount of carbon etc...
What you’re saying is that there is essentially no difference between climate science and the “harder” sciences, whereas economics on the other hand is a social science, i.e. not a science at all, thus climate science pwns economics. Just think about this for a second. Exactly how is the issue settled? Can you reconstruct it for me?
The problems that economics faces are exactly the same as the problems that climate science faces: the complexity of the system, the impossibility of experiments, questionable data, and the overt politicisation of results.
Economics is a tool kit of mathematical models, from the simplest univariate constrained optimization problem, all the way up to dynamic stochastic models of the whole economy. There is no possible economy that cannot be modelled using these methods, just as there is no possible climate that cannot be modelled using GCM (nothing to do with psychology in either case). It’s as easy as pie to fit a regression line to a set of data points after the fact!
As John von Neumann said, give me four parameters and I can fit an elephant; with five I can wag its tail.
These models do not necessarily prove anything about anything, because all they show are the projections that the models are designed to produce. As such, they fall victim to the Lucas Critique (of course, so does Lucas, but that’s another story—oh wait, no it’s not, it’s the same story: that’s my point).
Consider a basic neoclassical growth model (the Cobb-Douglas production function):
Y = A(L^α)(K^β)
Where Y is output, A is total factor productivity (technological change), L is labour, K is capital, and α and β are output elasticities.
Pretty straightforward, eh! Who said economic development was hard?
Consider a basic greenhouse model:
Global Warming = 0.36 x (33°C) x [(Total Forcing) ÷ (Base Forcing)]
Again, pretty straightforward.
What do the models show? The models don’t necessarily show anything. Like I said, it’s as easy as pie to fit a regression line to a set of data.
It should be obvious that neither model is going to generate any large discontinuities. How do you feel about this? Consider the phase space of the climate—it’s absolutely huge, and massively complex. The climate exhibits discontinuous transitions from one position to another within this space (e.g. in 1976). It is not possible to accurately model this, even if plausible results are generated (i.e. results that lie within the boundary conditions of the climate). Plausible results don’t mean a whole lot. See also: macroeconomics.
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