I haven’t read the original Limits to Growth (LtG). I’m not sure if I’ll get around to it. But I’m definitely going to read through this paper on comparing real world data to predictions made by the LtG models (even though it apparently came out in 2008 – how did I miss this?).
Apparently the original LtG work was based on a set of models, that included variables like birth rates, death rates, resource consumption, and food per capita (a crude variable for the food available). Although it’s been described as overly pessimistic, it apparently didn’t predict crashes until the mid-21st century. Say, about forty years from now. And it turns out that although the modelling (quite basic stuff; I think I may even be able to get my head around the equations) was done back in 1970, nobody’s compared the real world data to the different scenarios used in LtG.
As I said, I’m still hoping to work my way through the recent CSIRO paper (A comparison of the limits to growth with thirty years of reality, G Turner, CSIRO, June 2008), with the in depth comparisons. For now, some charts. In each one the blue line represents the stabilised model; basically, from what I understand, the one that’s sustainable. Other models (green and red) are variations on crashes. And the purple is the data that we have so far.
So Figure 2 gives us population levels; we’re on track for red/green, not blue.
So Figure 3 gives us birth rates; apparently we’re above average on this. This is a complicated one (for reasons to do with how crude a measure simple birth rates is, when in fact it varies extensively in different parts of the world; but for now notice the higher level trends).
Figure 6 gives us services per capita. The paper goes into more detail, but essentially this isn’t services as it might be defined in the national accounts; it’s a narrower focus, with less on luxury consumption on more on core services.
Figure 7 is food per capita; how hungry are we going to be?
Figure 8 is industrial output per capita.
Figure 10 is pollution.
And Figure 9 is non-renewable resources. Which comes to one of the more interesting points – why aren’t people taking this stuff in a more alarmist fashion? I found some interesting discussion of at the Lowy Interpreter blog – Are we testing the limits to growth?
Commodity prices and the like are a whole other issue, that I won’t get into here – but I’ll just note that I found Jared Diamond’s Collapse persuading, in providing examples of societies that have previously come up against resource constraints.