"This was shown recently in an analysis by Charles Hall and John Day "

Actually, no. Their analysis didn't show that at all. In fact, it showed that it did quite badly. As I said then:

First, the Limits to Growth predictions, as presented by the article, aren't very good. The birth and death projections are off quite badly (as Pitt notes, the "actual birth rate" presented in the article is dramatically incorrect). The population and industrial output per capita projections aren't any better than mainstream projections. The pollution projection cherrypicks worst offenders (CO2 and nitrogen), and yet even so misses quite badly (a projection of 3x 1972 levels, vs 2.0 and 2.1, respectively). The resource projection has to cherrypick light-sweet-oil and copper to look good (and there are some sharp objections earlier in the comments to the copper depletion assessment, to which I'd add that copper has very good substitutes for most of it's uses, and recycles very well). The only major resources that seem to fit the 50% depletion prediction are soil and fish, and calculations or sources aren't provided.

2nd, it hangs its resource case almost entirely on peak oil, and quickly dismisses wind and solar because they're not yet large energy sources. Yet, wind is cost-effective, has high EROEI, and an enormous resource base.

Both wind and solar are growing much faster than fossil fuels (roughly doubling every 2-3 years), and yet they say "the annual increase in the use of most fossil fuels is generally much greater than the total production (let alone increase) in electricity from wind turbines and photovoltaics." This is highly misleading. As an analogy, one could say that in the early 1980's that "the annual increase in the use of land line phones is generally much greater than the total production (let alone increase) in cell phones." Wind was about 1/3 of new generation in the US in 2008. It could easily provide all new generation in 5 years, and then start replacing coal.

Clearly, the overall fossil fuel resource base has declined much less than the 50% used in this article. More importantly, if one includes wind and solar resources, there is no significant decline at all - the whole question of energy "resources" becomes unimportant. Instead, we're looking at questions of investment and transition, which are entirely different.

Gail,
The "Limits to growth" focused on food, pollution and resources. Certainly food and mineral resources which had 10-50 years reserves in 1970 still have similar or more reserves. Crop yields have doubled,(in one scenario they assumed a food doubling by 2050, ie after 80 years not 40 years) but food could be an issue if everyone wants steak each day, pollution( mercury and lead) is not a serious issue, but CO2 is and in that sense the pollution issue is still a possible show stopper.
I would agree with Nick, about the Hall and Day article. Turner concludes about metals (page 26) " non-fuel materials will not provide resource constrains".

We need to remember that the limits to growth gave 9 scenarios to choose from, you can pick and choose to find a match in fact most match so far except for birth rates.

Since none of the scenarios predicted collapse until beyond 2009, what does it mean to say; "but in total, we are tracing the expected path fairly closely."

Refering to your "long experience ...save ourselves"remarks...

If I were rich,I would have these words engraved in stone in lots of prominent places.

As a farmer,I have waited for the rain....We have had(broadly speaking) no starvation ,and no forced migration of farmers in America in my time,but we can still talk to the children of the farmers who experienced th Dust Bowl.When times on the farm have been bad in my corner of the country,where we are mostly one horse(read tractor) farmers,folks have been able in many cases over the last six decades or so to save themselves by taking a part time-I am as serious as a heart attack-job doing an extra forty at a furniture or textile plant.Of course the plants have mostly either closed or move over seas recently.

Over the years,most of the local farms,while still very productive, have degenerated into part time operations maintained partly for such profits as may be had, but mostly for love of the land and the work.Of course we have a few farmers around here who still manage to make a full time go of it,but if you know them,you also know that there is usually some sort of cushion such as a wife who teaches second grade,etc.

Our children have seen enough ,long since, and moved on into other work.

Some day the stream of miracles that have arrived from the universities and industrial labs and garage tinkerers which,taken collectively, have enabled us to live as we do today will fail... for a while at least.Not totally of course,there is always rain if you wait long enough.

Right now it appears that just maybe the arrival of the new exploration and drilling technology which is bringing on the boom in natural gas will enable us to muddle on for a few more years of BAU.

Suppose this particular technology were still five or ten years away? I cannot envision any other result other than widespread war and famine (conceivably even within the US)if oil goes thru the roof,unless this new gas serves to keep the price of fertilizer within reach... for a few more years...

(some readers may think I am inconsistent, but if you read carefully,you will find that when I say something in favor of for instance hybrids, it is usually qualified adding under current conditions.)

Commercial farmers could switch from hybrids to open pollinated crops pdq if necessary, but no technology exists (that can produce the quantity of food needed today except bau big ag)which can also be implemented in the real world in short order.

I am all in favor of community gardening in any form,localization, etc, but I have grave doubts as to whether such movements will mature fast enough to prevent an eventual train crash if the ff supply crashes. Those who are actually working hands in the dirt in such areas will probably be able to save themselves.Latecomers will find the growth/learning/experience curve too much to deal with in most cases.

You can garden successfully even the first year in a good spot with a little help from an experienced friend, but a backyard that had all or most of the topsoil hauled off or buried when the house was built is not a good spot.Shade from the house, from cherished trees, from the nieghbors house or tree, is as good as a death sentence.

If you expect to save yourself(assuming you see a need to do so) by gardening/farming on a small scale with little or no input of commercial fertilizers or pesticides,you better get started NOW.iF YOU WORK REALLY HARD,while you can still get truckloads of leaves all bagged up at the curb for free in most towns,you can turn that subsoil into a garden spot in maybe four or five years.

"You're speaking of future technological advances. "

Well, the key thing here is that we have all the tech we need.

EVs and PHEVs are 100 years old.

Wind turbines are scalable, high E-ROI, and cost effective.

Solar is isn't quite as cheap or high E-ROI as would be ideal, but it's cost and E-ROI are more than good enough to suffice.

We don't need any breakthroughs, just a bit of routine engineering and a buildout which is relatively modest: well within the normal investment levels for the energy business.

The only real problem we have is that we would ideally expand renewables and PHEV/EVs sufficiently quickly that we'd make some of the current infrastructure obsolete. That's not a terrible cost, but it does create thorny political problems. Worse, a lot of people's careers would be obsolete, and they're going to fight that as hard as they can. We'd do well to try to help them, instead of just giving them disrespect and creating governmental gridlocks.

generally speaking progress in technology has fallen below expectations

That depends on your expectations.

If you were looking for fusion power, then sure. If you were looking for more efficient lighting, then CFL bulbs have delivered about a 4x improvement, and LED lights are poised to deliver another 4x within the next few years (they're already available, but still a little pricier). Similarly, there have been enormous improvements in batteries (Li-ion's power density is something like 4x that of 70s-era lead-acid), to the extent that electric cars are finally practical, and big improvements are continuing to come out (such as high-cycle-life lithium batteries). Also with wind and solar technologies - these are currently (wind) or nearly (solar) commercially viable, and are both highly practical, a far cry from their 70s-era status. Even boring old petrol cars have doubled in efficiency since the 70s.

I could go on, but hopefully you get the point: if you're not seeing substantial technological advances, it's because you're not looking.

Expectations for technological advance are a funny thing; we don't get to choose where breakthroughs will occur. We can bias things by putting more resources into one area or another, but it's never clear beforehand quite how close we are to a breakthrough. Accordingly, any individual expectation has a high chance of being unfulfilled, even though progress overall might be quite rapid. Fusion power might still be 30 years away, just like it was 30 years ago, but wind and solar power are now viable. The net result is a new energy source, even though 30 years ago we might have expected it to be a different one.

Technological advances may buy us time, but without 'control', at the end of the day they will only help to deplete our resources more efficiently and more quicly.

Exactly. Very dangerous in case of conventional oil. I read several times that secondary recovery delays the peak of fields, however that the decline past peak could be much steeper. Easy to imagine. And oilcompanies are not different from other companies. They want to sell as much of their stuff as possible and don't care about the fate of the rest of the world. The 'oil and gas experiment' can be done only once, and it is done in a 'stupid' manner.

switch to a wind powered (or even better, a gen-IV nuclear powered) ammonia economy

I think PHEV/EVs is the sensible path. I assume ammonia requires some conversion of vehicles, and it seems to be kind've a pain to handle.

If ammonia requires some conversion of vehicles, I don't see an advantage over PHEV/EVs. Do you have more info?