It is time to stop quivering in our boots in pointless fear of the future and just roll up our sleeves and build it.
- Ray Pierrehumbert

Sunday, December 14, 2008


Anything that can not be sustained eventually stops. Given that our whole way of living is unsustainable, the next question is "when?" The exponential growth of human impact on the planet will eventually cease, and the curve will take some other shape. When will the growth curve break?

(Modest clarification for the mathematically inclined: We do not know what shape the curve will take when the exponential stops growing, but it will be something other than exponential growth. After the point of inflection, the long term average of human impact on earth necessarily must stabilize or decline, possibly with superimposed wobbles and swings of various shapes. At some point in the persistent growth, human impact reaches or exceeds the long term sustainable average. Necessarily something else happens. Now we have to decide what. Arguably that point has been reached, and indeed that is what I believe.)

So, when? To be more specific, is it now? It seems to me that the present economic event is already big enough that it is likely to appear to the eye of the historian of future generations as a notable event. It may well look like the first major disruption of the impact curve rather than just a big glitch that is superimposed on that curve.

If so, if the great inflection is now, it is a drastic mistake to confuse the inflection with a recession. In a recession we should arguably go on doing what we've been doing in the past, and somehow we'll wander out of it. But if this is the inflection, what happens in the future depends sensitively on how we react to it. It is necessary to accept that impact has peaked or soon will peak, not just in greenhouse gases, but altogether.

It is not impossible that clever enough contrivances may decouple "money" from "impact". What I mean by this is that we somehow change our incentive systems so that people enhancing sustainability profit and those detracting from it pay.

To be sure, there are gestures in this direction, but systematically the incentives are almost universally perverse. There are good historical reasons for the perverse incentives and it will be a very delicate matter to reverse it.

Rewarding sustainability is by far our least disruptive path. Humans don't change easily, and time is short. If we weren't in a hurry, I'd consider changing the culture to something less driven by financial incentives, but given our time constraints that idea will not work. I think the most promising escape route is to play around with incentives so people are rewarded for more benign behaviors and penalized otherwise.

This won't be easy but any alternative I see is much more severe.

Update: Gloomy? Moi? Check this out. H/T Dennis at Samadhisoft.


Dano said...

The exponential growth of human impact on the planet will eventually cease, and the curve will take some other shape. When will the growth curve break?

Being stuck in my disciplinolatry, I have to point out that there is no reason to believe human growth curves are any different than any other species'; therefore, I assert that we are growing (population, impacts, waste, complexity, etc) on a sigmoid curve.

This allows your inflection topic to have more cogency, and allows us to realize that humanity is subject to the laws of nature.

This IMHO answers your implicit question about what shape it will take.



Michael Tobis said...

There are plenty of reasons to suspect otherwise; consider (yet again) the matter of Easter Island.

Dano said...

Sure, Michael, per Collapse or the interesting book I'm reading now: An Environmental History of the World.

What gets studied and debated is the shape of the curve off of the expected sigmoid.

That is: will we stay on the trajectory or will our policies change the shape?

Your implicit assertion that the curve will plateau then steeply decline (b rather than a) is my suspicion as well.

If this is indeed a plausible scenario, then our policies need to change to ensure the negative slope is shallow, not steep - for moral and ethical reasons.

Will we change our ways? My glass is half-full, but it is half-full of groundwater tainted by big ag.



Michael Tobis said...

I think the main thing that nature enforces is that the curve eventually reaches a maximum.

"Human nature" probably adds the constraint that we won't be ready when the maximum arrives. Or weren't ready when it actually arrived, perhaps.

What it does after that is up to us. If we respond to it like a regular, perhaps a bit unusual "business cycle", we will miss a great opportunity.

Michael Tobis said...

Dano, I looked at your curves. I hope you understand that A and B show the same thing. The confusion between quantities and their growth rates is a big problem in thinking clearly about these matters.

John Mashey said...

1) Predicting inflection points is always tough. In my old days as microprocessor and systems designer, I used to have to do this all the time. Often, the crucial curve wasn't one thing, it was the ratio of two things.

Example: cost/bit of DRAM memory versus cost/bit of magnetic disk. In the version of the standard computer architecture book, circa 1990, an exercise was to figure out when DRAM would overtake disks in cost/bit pervasively, as the former was improving faster than the latter.
Then, disks started improving much faster, and the question disappeared from the next edition of the book. Companies thinking they'd build complete disk-drive replacements ... didn't.

The high-tech universe is relevant because some changes happen *fast*, i.e., they are highly visible train-wrecks, not we-can0worry-about-this-later slow-motion ones.

2) For this topic, I recommend starting with the last page of Ayres 2005 on what happens to the US economy if we don't improve efficiency.

Dano said...

I hope you understand that A and B show the same thing.

I might be a little dense due to deadlines, Michael, but what I'm trying to say is that we have a choice for the slope after inflection - it can look like b, where there is a sharp downward slope, or it can look like a, where there is no indication of a decline.

That is: politicians and many others who make decisions seem to think or pretend that we can have a, but most who have had a biology course thinks it will look like b. The issue is the time scale for b. We are even starting to see economists (I'm thinking Brad DeLong) starting to talk out loud about whether we can have 'hard landings' or 'soft landings'.

So, it is in our power to have a hard landing or a soft landing. Will we choose, or just let things happen on a BAU trajectory (as in your comment at December 17, 2008 9:02 AM)?



Michael Tobis said...

Dano, yes, but you have hit upon an important secondary problem. I understand that the shapes are different in the two graphs, but they are redundant; they show exactly the same data, one in grams and the other in delta grams per day.

This distinction is so important in thinking quantitatively. An effort to make the point to the general public is here, but I am not sure it succeeds.

I expect you know the distinction between a quantity and its integral, but most people don't. So choosing this pair of graphs raises issues rather than settling them. In fact they are so closely related that I wonder why they are both presented. It appears redundant to me.

None of this is to say I disagree with what you are saying, Dano, just that the example raised other issues for me.

Dano said...

Michael, yes.

I'm just focusing on the shapes of the lines, not the quantification or the labeling of the axes.

We operate as if the shape of a is a given, but we know b is more likely. Well, some of us know.

Perhaps part of our misfiring here is that I'm working on a paper right now that looks at making scientific information actionable, and another that takes that action and makes it happen on the ground, so I might be a little addled and unclear.

Nevertheless, how we describe problems to make folk understand is an important theme on this blog - thank you - and how we usefully describe our current trajectory [and the fisheries depletion graphic] is what we as a society need to be focusing on.



Hank Roberts said...

An earlier set of curves, from Catton's _Overshoot_