Living earth simulator - I don't think the primary purpose of the simulator will be to make predictions. As you say, some things are inherently chaotic and unpredictable.
From the BBC report: 'It would be able to predict the spread of infectious diseases, such as Swine Flu, identify methods for tackling climate change or even spot the inklings of an impending financial crisis, [Dr Helbing] says.'
This is the guy behind it. Dr Novella, you know a lot about infection diseases. Do you think that this guy has a clue about the complexity of his undertaking? He reckons that already he's identified 70 sources of data. He'd need to bump that up by many orders of magnitude to even start to track all the passengers leaving an area of infection, cross matching against their individual susceptibility to the disease and their exposure, or personal contacts with others who may have been exposed. And so on.
It is an interesting project and I can see how it might have some utility, but it's real utility will be determined after it is up and running and people think of interesting ways to use the data.
GIGO. Except that the machine through which the garbage will be processed will also be garbage. We not only don't know enough, there's a respectable argument to be made that we can't
... So don't dismiss the LES just because it's not a Hari Seldon device. Twenty years ago a colleague of mine dismissed the internet because he didn't think that people would adopt it as a means of communication. He literally said it was going to "go the way of the CB radio."
I dismiss LES because
it is a Hari Seldon device. Even as a pretty damned credulous teenager I thought Asimov was over-reaching by far. I was somewhat relieved when the existence of the Second Foundation was revealed.
My central point is that a projection/prediction/trend identification can be very dangerous. The more 'scientific' it seems -- because really, really big computers were used and some tens of billions of dollars were poured in and lots of bright people are involved -- the more dangerous it will be. The scientists for the most part could well be sensible, but once the outputs get into the hands of politicians and other enthusiasts, they will insist on expensive remediations of imaginary future problems, often at the expense of resilience. Right now here in Australia there is a debate going on about whether the flood mitigation dams were used properly. The argument is that they were kept too full because of long standing predictions of permanent climate-change-induced drought. This is still playing out so it may well be wrong, but it illustrates the point.
Speaking of which, I am surprised by your use of the anecdote about your colleague's false prediction. The success of some technology -- in quite unexpected ways -- says nothing at all about any other technology. I know that you used this to buttress your suggestion that different surprising uses may be made of the project's output. Well, I can think of one: if the output is rigorously analysed after each run and then compared to the real world as it develops, it might help us keep our predictive ambitions in check.