First, consider that the 2020 paper assumes-as-given that the various scenarios adequately capture the range of possibilities, and that the model used accurately projects forward what the model assumptions would mean in practice. My fundamental problem with this is that it implicitly assumes failure is inevitable. The SW and CT examples don’t lead to collapse, and do assume increasing efficiency of resource use, but neither includes the possibility of substituting renewable resources for non-renewable ones. This was reasonable in 1972, and plausible even in the early 2000s, but is a denial of current physical reality here in the 2020s. The remaining problems to such a transition involve a lot of hard engineering, but achieving such is fundamentally social/political rather than technological. We have a large enough set of plausible pathways and emerging solutions to the critical problems that with adequate investment, enough should pan out to become practical.
Second, relatedly, the original paper and subsequent follow-ups do not try to account for behavioral shifts and substitutions caused by changes in the market prices (relative and absolute) of different resources as some become more scarce. They talk about physical capital diversion as extraction difficulty increases, which is fine, as well as lag times in adaptation, also important, but not what might drive any other kind of shifts. This… seems to me to be the resource equivalent of the lump of labor fallacy. It just assumes that capital extracts non-renewable resources and irreversibly converts them to near-term human welfare, and concludes that making conversion more efficient is insufficient to achieve sustainability. Which is a logically correct deduction, but doesn’t require a study or model to demonstrate; it’s basic physical fact. In practice, as things become scarce, their price goes up, and people look for substitutes. Those substitutes include (at some falling-over-time extraction difficulty) renewable materials and energy sources, whose potential supply does not diminish with time (at least not on any timescale under consideration). They also include changing how and where we live, and what we actually use our resources to make and do. With the right renewable resource technology, it is not clear that resource supply becomes the limiting constraint on humans until the Sun renders the Earth uninhabitable, and possibly not until the heat death of the universe.
Third, the core premise of the 2020 paper is that we’re looking at recent data to figure out which trajectory we’re closest to. That’s great, I’m all in favor. I love using data, simple assumptions, and crude models to investigate these kinds of hard forecasting questions. It does this by simple counting of NRMSD across metrics, which… just seems utterly and obviously inadequate. The metrics are not anywhere near equal in importance for the questions we’re claiming to investigate (“CO2 pollution” is counted as 1, as is “education spending”—these are not the same). The differences between scenarios are mostly quite small (except for SW), many well within their uncertainty thresholds on the data. The paper is honest about this, which is great. But even on its own terms, the two closest matches are BAU2 and CT, which are completely different in their assumptions and implications. The paper seemingly does not even really try to figure out what’s actually going on beyond “We’re clearly not trying to get to SW.” Which is true. We’re not.
So I guess those are the main ones. In 1972 the authors didn’t know what would happen, and made what seems to be an honest, reasonably thorough attempt to evaluate the possibilities they could imagine. Unfortunately they could not imagine a large chunk of what has actually happened since then: Their CT scenario does not account for replacing non-renewable resources with renewable ones. Subsequent updates (including the Herrington 2020 one) do not even try to fix this. That omission is fundamentally why the 1972 paper concluded that an end to growth, with or without collapse, was inevitable. Failure to update on what has actually happened since then is something I can no longer consider to be an honest mistake. It is, at best, intellectually lazy. At worst, a sign of politically or ideologically driven commitment to degrowth regardless of economic and technological options to obviate any need for same.
Right, could I ask what exactly you agree and disagree with about her assumptions?
Ok.
First, consider that the 2020 paper assumes-as-given that the various scenarios adequately capture the range of possibilities, and that the model used accurately projects forward what the model assumptions would mean in practice. My fundamental problem with this is that it implicitly assumes failure is inevitable. The SW and CT examples don’t lead to collapse, and do assume increasing efficiency of resource use, but neither includes the possibility of substituting renewable resources for non-renewable ones. This was reasonable in 1972, and plausible even in the early 2000s, but is a denial of current physical reality here in the 2020s. The remaining problems to such a transition involve a lot of hard engineering, but achieving such is fundamentally social/political rather than technological. We have a large enough set of plausible pathways and emerging solutions to the critical problems that with adequate investment, enough should pan out to become practical.
Second, relatedly, the original paper and subsequent follow-ups do not try to account for behavioral shifts and substitutions caused by changes in the market prices (relative and absolute) of different resources as some become more scarce. They talk about physical capital diversion as extraction difficulty increases, which is fine, as well as lag times in adaptation, also important, but not what might drive any other kind of shifts. This… seems to me to be the resource equivalent of the lump of labor fallacy. It just assumes that capital extracts non-renewable resources and irreversibly converts them to near-term human welfare, and concludes that making conversion more efficient is insufficient to achieve sustainability. Which is a logically correct deduction, but doesn’t require a study or model to demonstrate; it’s basic physical fact. In practice, as things become scarce, their price goes up, and people look for substitutes. Those substitutes include (at some falling-over-time extraction difficulty) renewable materials and energy sources, whose potential supply does not diminish with time (at least not on any timescale under consideration). They also include changing how and where we live, and what we actually use our resources to make and do. With the right renewable resource technology, it is not clear that resource supply becomes the limiting constraint on humans until the Sun renders the Earth uninhabitable, and possibly not until the heat death of the universe.
Third, the core premise of the 2020 paper is that we’re looking at recent data to figure out which trajectory we’re closest to. That’s great, I’m all in favor. I love using data, simple assumptions, and crude models to investigate these kinds of hard forecasting questions. It does this by simple counting of NRMSD across metrics, which… just seems utterly and obviously inadequate. The metrics are not anywhere near equal in importance for the questions we’re claiming to investigate (“CO2 pollution” is counted as 1, as is “education spending”—these are not the same). The differences between scenarios are mostly quite small (except for SW), many well within their uncertainty thresholds on the data. The paper is honest about this, which is great. But even on its own terms, the two closest matches are BAU2 and CT, which are completely different in their assumptions and implications. The paper seemingly does not even really try to figure out what’s actually going on beyond “We’re clearly not trying to get to SW.” Which is true. We’re not.
So I guess those are the main ones. In 1972 the authors didn’t know what would happen, and made what seems to be an honest, reasonably thorough attempt to evaluate the possibilities they could imagine. Unfortunately they could not imagine a large chunk of what has actually happened since then: Their CT scenario does not account for replacing non-renewable resources with renewable ones. Subsequent updates (including the Herrington 2020 one) do not even try to fix this. That omission is fundamentally why the 1972 paper concluded that an end to growth, with or without collapse, was inevitable. Failure to update on what has actually happened since then is something I can no longer consider to be an honest mistake. It is, at best, intellectually lazy. At worst, a sign of politically or ideologically driven commitment to degrowth regardless of economic and technological options to obviate any need for same.
I’ll need to go back and reread the 1972 Limits to Growth, but then I’ll try to put something together
thank you