The last few weeks have been tedious; I’m tuning the simulation to get everything working right. I fear I may have bitten off more than I can chew; the complexity of this simulation is proving to be daunting -- or perhaps my standards of realism are higher. In any event, it’s very difficult getting everything to come out right. I finally got the null scenario (in which the player does nothing) coming out right. GDP, energy usage, industrial output, pollution, and so forth all seem about right. That in itself is a big step forward, but now the task is to get it all working right when the player starts making changes.
The easy way to do this is to start off with coefficients that insure that the player’s actions have just a tiny effect, and then ramp up the strength of the responses. At the same time, however, I have to insure that the player’s actions have SOME effect. It’s a balancing act. Just now I’m facing a weird situation in which the application of a reasonable carbon tax ($30/ton) has its desired effect of suppressing use of fossil fuels, but much later in the game, the GDP rises so high that fossil fuels make something of a comeback. Not good. I think it arises from my linear extrapolation of fossil fuel supplies at prices at $20 (2011 prices are $4). Perhaps I need to flatten the supply versus price curve at those prices.
Another problem I’m struggling with concerns electric cars. In the current simulation, a high enough GDP triggers extremely high use of vehicles, which in turn drives up demand for gasoline late in the 21st century. That’s absurd. The countervailing factor is supposed to be mass transit, but it doesn’t expand quickly enough. The solution I am contemplating is to add a new factor for electric vehicles. It is obvious that the future belongs to electric cars. By providing a conversion to electric cars, I can eliminate demand for gasoline. Moreover, showing the player the inevitability of the transition to electric cars offers considerable educational value. But if I make this a factor, I should offer the player a means for encouraging the transition. Currently, the only lever the player can push is the gasoline tax. This may not be enough.