There's two big missing facts that I've never noticed Murphy in particular acknowledge: the 1980s peak in global births -- population growth is now driven entirely by decreasing mortality -- and the late 20th century decoupling of energy consumption from economic growth.
Both point to an obvious counter-theory: That industrialization was a centuries-long process, involving exploding populations and energy consumption, that in much of the world has come to an end. The nice little exponential lines are overfit to a particular span of human history and stopped being predictive somewhere in the 20th century.
Also, most of those peaked resources are not even vaguely scarce. I'm not even sure what it would mean to run out of iron ore or bauxite -- a large fraction of the Earth's crust is iron- and aluminum-bearing rock, and the definition of "ore" is "the particular chunks of rock and dirt that are economically viable to extract metal from". Production peaked because of limited demand and lowered shipping costs that made foreign supplies cheaper.
the late 20th century decoupling of energy consumption from economic growth.
If you bothered reading my post and links, I've gone into extensive length on how economic decoupling hasn't happened and that the observed increase in efficiency is fully consistent with complex systems / dissipative systems theory.
The problem with technical capital is that it depreciates rapidly. While some Roman infrastructure remains standing to this day, odds are that most of today's electronics won't be functioning in 20 years, let alone 2000.
On peak minerals: Leibig's Law of the Minimum states that it's the least abundant resource that constrains your growth. Pointing out that there's plenty of X when Y is a limiting factor doesn't buy you much. I'd look very closely at ag productivity.
Heinberg and others go into the issues of working from low-yield ores. Most significantly, energy requirements scale inversely with or yield, and the critical problem would be a technological collapse which would lapse beyond the stage of a feasible reboot. While you _can_ extract minerals from dirt or seawater, the energy and capital requirements are immense. Citations on your claims of foreign supplies would be appreciated.
I appreciate the dialog you're already having, but I thought you might like to know that some of the statements you're making are causing my skepticism of the whole argument to increase, not decrease. I'm not knowledgeable enough to weigh in, but it might be useful for you to know what arguments work well and which don't.
Here's what I noticed in your reply that I found myself questioning your authenticity:
1. Your first sentence is long and diminutive to the reader. I don't know who the other person is, but maybe they did read your post and links? I'm not sure. I also am highly skeptical of anyone that refers to their extensive anything on anything. It really highly signals "quack" to me. Again, I'm not trying to suggest you are.
2. Your first sentence includes a number of terms that demand unpacking. This is really strongly related to the first point, because I feel like as a reader I'm being talked down to and then hit with some deep jargon that I don't understand. Perhaps I'm just out of my league on this conversation, though.
3. Your argument on peak minerals doesn't seem to make sense to me. It's one of those things where, I read it and it feels very strongly like when I read a staunch libertarian/Austrian economic argument between friends on Facebook and see someone cite a universal law of microeconomics and then they use it to justify something much larger or more complex. Looking up Leibig's law didn't help me here. I'm just left a little more bewildered and even if I read and interpreted Leibig's law as being one hundred percent correct in its original formulation, there's a gap in my intuition between that and your use here, as near as I can tell.
Your first sentence is long and diminutive to the reader.
He specifically reiterated without support an assertion of a fact I'd addressed specifically, at length, and with considerable real world data. A finer point: I wasn't dismissing him specifically, but his actions. I'm not here to make friends or even particularly to persuade, but to expand my own understanding of a subject I find of absolutely crucial importance. Occasionally I find merits to discussing matters with those holding opposing viewpoints.
Some guy came up with this concept called "Graham's Hierarchy of Disagreement". You should check it out:
As to decoupling: I'm not aware of anyone who's specifically looked at GDP/quad data, but I had, using public data (the blog post consists of a set of graphs with links to the original from Wolfram+Alpha), and a bit of commentary. You're welcome to agree or disagree with specifics, though an ad hominem without any other basis for disagreement doesn't do you much credit. You're at levels 2 & 3 of the hierarchy. bcoates managed to attain level 3.
Though as a DDG fan I've got a newfound softness for quacks.
Your first sentence includes a number of terms that demand unpacking.
Which? "Economic decoupling" or "capital depreciation"?
First: yes, this is a complex area, it's got a bit of its own language. That's typical of any advanced field. That said it's not overly complex, though you've got to be willing to take and bin a fair amount of conventional wisdom.
For more on decoupling, associated with resources in general, see:
⚫ Exhaustion of any extractive resource follows a curve similar to that M. King Hubbert demostrated for oil in the 1940s and 1950s, accurately predicting US peak production in 1970, and a global peak between 2000 and 2010[1]. Data are a little hazy on global production yet, but it's clearly been flat despite massive increases in market prices and capital expenditures by oil companies. See Shell Oil's profit warning issued just this week. You're welcome to read my take at http://reddit.com/r/dredmorbius or The New York Times, whichever you find less quackish: http://www.nytimes.com/2014/01/18/business/energy-environmen...
⚫ Mining costs increase with falling ore grades. Heinberg cites this OilDrum piece: http://anz.theoildrum.com/node/6974 "As a rule of thumb, when the quality of the ore drops, the amount of energy required to extract the resource rises". The rationale: lower grade means more overburden and tailings to remove -- you've got to mine deeper, or excavate a large area, or filter more seawater, or go through whatever it is that's your source for the mineral.
Leibig's Law is a separate observation to the issue of peak minerals -- it's not describing how or when minerals peak, but what the effect of their peaking is on the remainder of the system. For a critical mineral (say, phosphorus) to peak would have dramatic effects throughout the system. Having enough cobalt or gallium for iPhones won't do much if you can't grow food to feed the iPhone user.
Thanks for explaining more. I didn't respond because I realized that we didn't agree on terms, and dictionary arguments are boring. I was using "decoupling" in the sense of "what happens to an overfit model after it stops working", and hadn't really noticed that your reddit post was also using the term to argue against something I don't claim (or particularly care about), "reduction in power accompanied by increases in GDP".
I'll admit that my post was more a general reaction to Prof. Murphy's chronic abuse of statistical modelling, visible in the post you linked to "The Real Population Problem" where he applies a rather incoherent statistical model ("Population growth is exponential, but the exponential rate keeps changing", which is another way of saying "Population growth is not exponential"), while ignoring the real story on population, flat or slightly declining total births per year.... and his even more baffling and famous post, http://physics.ucsd.edu/do-the-math/2012/04/economist-meets-... where he plops down a tight exponential fit that clearly applies to the 'Industrial Manufacturing' era and visibly and extremely fails to model after that (it's a log plot, that post-1970-ish curve indicates a massive, model-falsifying difference between model and observation).
Economic modelling is hard enough for the world we live in, a world where we're mining 0.02% Uranium from the ground instead of 10+% is so unlike anything we know that making predictions about it is hubris.
I generally don't find peakery interesting because I don't accept the fundamental premise (that you can model future resource availability at all using historical consumption volumes), so I'm not even at the point where more production (=consumption) data, however well sourced, is compelling.
we didn't agree on terms, and dictionary arguments are boring
If someone can come up with a dictionary definition that defends their use, I'll accept that there are multiple common uses of a term. Sometimes utterly contradictory ("inflammable", "citation", "oversight", etc.) It's when I find people dismissing common terms or arguing against the dictionary that I rapidly lose interest. What's the context/field for your use of decoupling?
"Population growth is exponential, but the exponential rate keeps changing"
Mapping different fits to different portions of a curve is neither unknown nor invalid. A mathematical model simply describes the behavior of data. The underlying mechanism isn't itself described by the model (which itself is something of an orrery). Instead, as Murphy notes, population was responding to markedly different circumstances at different points along the line. You've neatly skipped over his explicit recognition of this: "What accounts for the discontinuity in slope?", and:
Plotting global population in the last thousand years (below), we see a few breaks in the slope. For most of this period, we saw a modest 0.12% growth rate, amounting to a 600 year doubling time. Around 1700, the rate stepped up to 0.41%, doubling every 170 years. The next break happens around 1870, jumping to 0.82% and 85 years to double. Then around 1950, we see another factor-of-two rate jump to 1.7%
What happened at those dates? 1700 marks the nascent beginning of the Industrial Revolution (Newcoman's steam engine pumps in coal mines) and more abundant coal. 1870 marks (roughly) electricity and modern sewerage, sanitation, antisceptics, and anesthesia. 1950 marks the beginnings of the Green Revolution as well as the great advance of manufacturing and post-war renaissance around the globe. The earlier 0.03% growth to ~6000BC marks the period prior to advanced agriculture and urbanization. Noting where your tidy mathematical model breaks is just as important as seeing where it fits.
In the "Economist" dialog, you're failing to recognize the point that it's the economist who's positing eternal growth:
Physicist: "So what’s a typical rate of annual energy growth over the last few centuries?"
Economist: "I would guess a few percent. Less than 5%, but at least 2%, I should think."
The remainder of Murphy's analysis is to demonstrate the patent absurdity of this.
I've observed that this leads to a number of fairly typical responses from Murphy's critics:
⚫ He's extending a growth trend which has broken down in recent years (your objection). The point is that the energy growth he demonstrates is tightly coupled (correlated) with economic growth. And if you want the latter, you're going to need the former.
⚫ Economic growth has been decoupled from energy growth. The graphical evidence I've shown suggests otherwise.
⚫ Technology will fix everything. "Growth doesn't depend on increasing material consumption at all". /u/geezerman at reddit and Tim Worstall at The Telegraph essentially make this argument.
⚫ "There is no energy/resource shortage". Humans will find and tap endless sources of new energy and raw material ... somehow.
I don't accept the fundamental premise
So: what would be a valid basis for a model of future resource availability? How do you address Hubbert peaking and depletion curves and the accuracy with which they've predicted known peaks in local, national (US and elsewhere), and by appearances, global oil production, as well as other resource peaks?
Rubbishing models without presenting a more accurate one yourself (or pointing at one) isn't science, it's denial.
Both point to an obvious counter-theory: That industrialization was a centuries-long process, involving exploding populations and energy consumption, that in much of the world has come to an end. The nice little exponential lines are overfit to a particular span of human history and stopped being predictive somewhere in the 20th century.
Also, most of those peaked resources are not even vaguely scarce. I'm not even sure what it would mean to run out of iron ore or bauxite -- a large fraction of the Earth's crust is iron- and aluminum-bearing rock, and the definition of "ore" is "the particular chunks of rock and dirt that are economically viable to extract metal from". Production peaked because of limited demand and lowered shipping costs that made foreign supplies cheaper.