Another Look at "The Limits to Growth"

My thoughts exactly. Fixed the graph to reduce bias: http://dl.dropbox.com/u/3750008/Screenshots/r.png

You can't tell whether it's going to rain five days from now very reliably, but you can predict within a degree the average monthly temperature in any city in the world, for any month of the year, five years from now. Of course there are unforeseeable events, but that doesn't mean everything is unforeseeable.

In this case, we've had 40 years to test this forecast, and it looks like they've done a pretty reasonable job forecasting the key variables they were forecasting, 40 years in the future. That seems like a good validation of their model, and we should expect it to do nearly as good a job for the next ten years at least, if not 20.

So I don't think they should be taken as a "work of fiction", even if they might be wrong. The model should be taken seriously, and we should attempt to improve it or propose better models, even if those models have more uncertainty in their predictions.

There's a big difference between predicting an apocalypse based on a psychotic episode and predicting an apocalypse based on a dynamical model of the key variables in a world system.

Weather patterns are extremely complex and yet fall within a certain set of bounds. A swing of ten degrees is perceived as a dramatic change. This is because the numbers involved are relatively small.

Resources and populations have much wider swings and the forces that perturb them need time to have an effect. The numbers involved are millions of times larger than temperatures. There's also much higher inertia than the weather.

It's impossible to predict the precise number of births tomorrow, or the amount of coal extracted to the ton, but you can come up with a very accurate estimate for the course of a year or a decade with the right data.

We can't predict the weather five days out, but we can predict the climate ten years out.

False analogy.

"weather forecasting" involves fine-resolution (in both space and time) predictions. This is known to be difficult to do reliably ("butterfly effect").

This is more akin to climate analysis: low-resolution in space (continent-scale instead of ZIP-scale) of and time (decades instead of 24 hours). Much more amenable to statistical modeling.

YMMV.

The point of the article is that this particular simulation did in fact accurately forecast mankind's future 30 years into the future, from 1970 to 2000. If you had made your argument against the model in 1970, you would have been wrong. The implication now is that since the model accurately predicted the last 30 years, we should also trust it to predict the next 30 years. You might still argue with the conclusions, but you need to be more specific in your criticisms than "these things can't be predicted", because according to the article, apparently they can be. At least for the last 30 years.

Agreed. These predictions assume that behavior never changes. Just like when gas prices skyrocketed a few years back and you could buy a SUV for a fraction of the value a year ago.

Another great example is oil. When oil was cheap and plentiful, people screamed "we're running out!!". Prices went up and suddenly it was economically viable to frack and extract from tar sands. Boom, we have a bunch of "new" oil.

I don't think that is true. As for as I recall, the World3 model includes price feedbacks like this.

But even if it didn't, one of the lessons of World3 is that it takes time for negative feedbacks like this to achieve equilibrium. If the feedback is slow enough, you get overshoots, and those overshoots either are (by definition) or could trigger (as a side effect) environmentally and socially damaging events. In the case of population, for example, the recovery after a large overshoot could take the form of mass famine or civil war.

There is another problem with the argument that many free market optimists make about energy: to actually scale up whatever fancy clean-energy technology happens to become economically viable in the future might require huge swathes of our economies to be reconfigured at an impractical rate.

To give an example, there are physical limits to how quickly you can ramp up the volume of solar panels, no matter how cheap the technology is, to do with quickly we can ramp up the production of pure silicon, build plants that make solar panels, and train engineers to oversee those plants and install those panels into the grid.

Of course, we can't quantify these limits for some mystery future technology, but we can play the game for known technologies, and it doesn't look good.

In particular, it seems that it is only really realistic to be off fossil fuels by 2050 if we start transitioning aggressively now using many different approaches --simultaneously. In other words, we need to place a lot of large bets, not just one large bet or several small ones -- see [1] for example.

Given the reluctance of the world's largest producers, consumers, and polluters to even get serious about one of these approaches, it seems pretty hopeless that we have the political will to execute on all of them, simultaneously, at global scale, as we need to.

As usual, the poor will suffer disproportionately.

[1] http://www.aaas.org/news/press_room/climate_change/mtg_20070...

I'm not very familiar with their model, but if the birthrate asymptotes to above the replacement rate, or goes back up, the population won't decline. So the economy might be a factor.

I'm not so sure about the energy side, we've got a number of folks who are making real progress in both solar efficiency and energy storage. We have new nuclear processes that were once derided (cold fusion) being quite durable (while most folks don't have a good explanation about what is happening, more and more of the community is convinced that something we don't know about is happening at these low energy levels) We are getting hints of some of superconductivity's secrets which has the potential to eliminate distance constraints on energy transport, and we know how to build nuclear plants that are walk away safe and can consume their own waste leaving behind some easily manageable and easily containable waste products.

Energy no object, it's a matter of harvesting it and dissapating the wasted heat.

After all, the sun send more energy to the earth in one hour than we use in an entire year as humanity.

What about pollution? In a way I feel very pessimistic, because I can't find a reason why humans wouldn't exploit every resource to the maximum. For example fish in the sea, wood in the rainforest (or just surface below the rainforest), air, oil...

I think humans will survive, but how much will we destroy before reaching equilibrium?

What other things look great, besides iPhones? The economy? The state of understanding between countries, with more and more of them acquiring nuclear weapons?