Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Monday, April 20, 2015

Climate change: can the Seneca effect save us?

The "Seneca Cliff" (or "Seneca Collapse"). The ancient Roman philosopher said "The path of increase is slow, but the road to ruin is rapid." A "Seneca Collapse" of the world's economy would surely reduce the chances of a climate disaster, but it would be a major disaster in itself and it might not even be enough.  

Nothing we do (or try to do) seems to be able to stop carbon dioxide from accumulating in the atmosphere. And, as a consequence, nothing seems to be able to stop climate change. With the situation getting worse and worse (see here for an example), we are hoping that some kind of international agreement can be reached to limit emissions. But, after many attempts and many failures, can we really expect that next time - miraculously - we could succeed?

Another line of thought, instead, has that depletion will save us. After all, if we run out of oil (and of fossil fuels in general) then we'll have to stop emitting greenhouse gases. Won't that solve the problem? In principle, yes, but is it going to happen?

The gist of the debate on the future of fossil fuel production is that, despite the theoretically abundant resources, the production rate is strongly affected by diminishing economic returns generated by depletion. This factor forces the production curve to follow a "bell shaped", or "Hubbert," curve that peaks and starts declining much before the resource runs out, physically. In practice, most studies that take into account the diminishing economic returns of production arrive to the conclusion that the IPCC scenarios often overestimate the amount of fossil carbon that can be burned (see a recent review by Hook et al.). From this, some have arrived to the optimistic conclusion that peak oil will save us from climate change (see this post of mine). But that's way too simplistic.

The problem with climate change is not that temperatures will keep smoothly growing from now until the end of the century. The problem is that we will run into big troubles much earlier if we let temperatures rise over a certain limit. Sea level rise, oceanic acidification, and land desertification are just some of the problems, but a worse one could be the "climate tipping point." That is, over a certain point, the rise in temperatures would start to be driven by a series of feedback effects within the ecosystem and climate change would become unstoppable.

We don't know where the climate tipping point could be situated, but there exists a general agreement that we should keep temperatures from rising above 2 deg. C to avoid a major catastrophe. From the 2009 paper by Meinshausen et al. we can estimate that, from now on, we should not release more than about 1x10+12 t of CO2 in the atmosphere. Considering that we have released so far some 1.3x10+12 t of CO2 (source: global carbon project), the grand total should not be more than about 2.3x10+12 t of CO2.

So, what can we expect in terms of total emissions considering a "peaking" scenario? Let me show you some data from Jean Laherrere, who has been among the first to propose the concept of "peak oil."

In this figure, made in 2012, Laherrere lists the quantities of fuels burned, with a "U" ("ultimate") measured in Tboe (Terabarrels of oil equivalent, see below for the conversion factors used). As a first approximation, if all the emissions were from crude oil, we would emit some 4.5x10+12 t of CO2. Things change little if we separate the contributions of the three fossil fuels. Crude oil, alone, would produce 1.3x10+12 t of CO2.  Coal would produce 2.8x10+12 t and natural gas 0.95x10+12 t. The final result is nearly exactly 5x10+12 t of CO2.

In short, even if we follow a "peaking" trajectory in the production of fossil fuels, we are going to emit around twice as much carbon dioxide as what some people (probably optimistically) consider to be the "safe" limit.

Of course, there are plenty of uncertainties in these calculations and the tipping point may be farther away than estimated. But it could also be closer; much closer. And we should take into account the problem of the increasing CO2 emissions per unit of energy as we progressively move toward dirtier and less efficient fuels. So, we are really toying with disaster, with a good chance to run straight into a climate catastrophe.

This conclusion holds in the assumption that the "peaking" scenario is not too optimistic in the amount of fossil fuels that can be produced and burned in the future. But these scenarios are normally termed "pessimistic" in mainstream studies, so that little would change as long as we work with nearly symmetric, bell shaped curves. At best, we can assume that peaking could take place a few years earlier than in Laherrere's estimate; but that still leaves us facing the very real possibility of a climate catastrophe.

Could we, instead, consider a different shape for the production curve? The symmetric "bell shaped" or ("Hubbert") curve is the result of the assumption that extraction is performed in a fully  functioning economy. But, once the economic system starts unraveling, a series of destructive feedbacks accelerates the decline. This is the "Seneca collapse" that generates an asymmetric production curve (the "Seneca cliff").

A Seneca shaped production curve would considerably reduce the amount of fossil carbon that can be burned in the future. Tentatively, if the collapse were to start within the next 10 years and it were to cut off more than half of the potential coal production, then, we could remain within the estimates of the 2 deg. C limit, hoping that it could be enough. Hubbert can't save the ecosystem, but Seneca could (maybe).

But, even if that came to pass, a Seneca collapse is a major disaster in itself for humankind, so there is little to rejoice at the thought that it could save us from runaway climate change. In practice, the only hope to avoid disaster lies in taking a more active role in substituting fossils with renewables. In this way, we can force the production of fossil fuels to go down faster than it would do as an effect of gradual depletion, but without losing the energy supply we need. It is possible - it is a big effort, but we could do it if we were willing to try (see this paper by Sgouridis, Bardi and Csala for a quantitative estimate of the effort needed)


Unit conversion

One Boe of crude oil = 0.43 t CO2 (

One Boe of coal = 0.53 t CO2 (calculation from and from 

One Boe of natural gas: 0.31 t CO2 (calculation from and from 


  1. Well, it may save us from burning fossil fuels, but it may switch to burn biomass in much bigger quantities, even at a damn fast pace than many will expect. Maybe we will go by a much worse direction: burning the plants that remove the CO2 from atmosphere...

    Just a thought.


  2. Peak oil, climatic disruption, 6th biomass extinction, inequality..., yes, an economic Seneca cliff is better than a human extinction; I also defend that could be better a quick and profound economic collapse, now. But an economic collapse could give to geopolitical wars (nuclear?) and the consequences could be even worst that climatic chaos (but, after the tippings points, biophysical chaos is not under human control and human wars yes).
    Our problem is how communicate this findings. It seams sci-fi!

    1. Oh, well, a nuclear war is a good illustration of a Seneca collapse (of the worst kind)

  3. I've been following the use of plant-based charcoal in soil as a method of soil improvement (less use of water, less use of fertilizers, less run-off of chemicals into surface and ground water supplies, increased yields, etc.). It has one additional good aspect: the charcoal is not decomposed by microbes, remaining in the soil for 500 to 1000 years. I remain mildly hopeful that the "International Biochar Initiative" might help with several aspects of the ongoing crisis. BTW, the concept is inspired in Euro-American literature but the "terra preta" of the Brazilian rainforest (man-made, before European contact). I think, however, the practice has a continuous cultural tradition in Japan.

  4. Seneca cliff could save us. That's good news, even if it's a major disaster for humankind. After all, isn't our modern world a kind of Titanic, with not enough lifeboats for everyone?

    The problem with renewables is that it takes oil to manufacture them, for mining and transport. Plus, there is the energy trap:

    What do you think of John Michael Greer's "collapse now and avoid the rush" strategy?

    I personally stick to Chris Nelder's timeline (it gets me acting):

    2014-2015: two good years left of business as usual
    2016-2017-2018-2019: three or four years before things really get difficult
    2019-2020: things really get difficult

    Or: il collasso del sistema economico globale comincerĂ  ad essere evidente fra 5 – 15 anni da ora,

    Not many people actually talk about Seneca cliff, thank you :-)

  5. I’ve found this post really interesting, professor Bardi. Putting together climate change, resource depletion and economic dynamics is not an easy issue.

    As I see it, you draw 3 scenarios:

    A) Energy crisis --> soft collapse (oil-to-coal transition, large land use changes), population growth continues --> runaway climate change --> end of story

    B) Energy crisis --> Seneca collapse (population collapse) --> most carbon is left undeground --> climate change decelerates and some decades or centuries further it stabilizes in a level to which survivors could adapt.

    C) Energy crisis --> Renewable revolution --> without population collapse, climate change decelerates and some decades or centuries further it stabilizes in a level to which survivors could adapt.

    If we take into account that so far modern renewable can be understood mostly as fossil fuel extenders, I can’t fully understand how it could be feasible a renewable revolution while our best energy resource -cheap oil- is already in decline, and many of our key mineral resources are close to their peaks.

    Moreover, let us imagine that after an ingenuity outbreak we manage to develop a high-EROEI modern-renewable infrastructure. Wouldn’t it allow us to burn that amount of fossil fuels that otherwise would be left underground –like Hubbert imagined about nuclear- so it would bring us back to scenario “A”?

    After all, in my modest opinion, we don’t need any new technology to feed the world, but some common sense and a little humility.

    1. "so far modern renewable can be understood mostly as fossil fuel extenders," So far....... but only so far.

    2. I'm sorry I cannot help seeing a renewable driven full-working industrial economy that agrees to leave recoverable fossil fuels underground as a second-grade miracle.
      Thanks for your post and for your answer.

    3. What we now see obscurely, as in a mirror, then we'll see, face to face.

    4. 'Through a glass, darkly'.

    5. 1 Corinthians 13:12 (English Standard Version, or ESV): “For now we see in a mirror dimly, but then face to face. Now I know in part; then I shall know fully, even as I have been fully known.”

      Prof Bardi's version (which I suspect is his translation from Italian) is more accurate than the King James. And it is entirely appropriate!

    6. From Latin: tunc videmus per speculumin aenigmate, nunc facie ad faciem

  6. This article discusses the current probabilities for 2°C in "human readable" form from the latest findings:


  7. The solution to the ecological, economic, geo-political and spiritual catastrophes engulfing humanity lies not in economics, ideology or ecological science but in psychology. We arrived in this calamitous situation because we never really faced up to the question of pathopsychological and spiritual Evil. The world is dominated by Rightists of different types, 'Rightist' being a silly euphemism for psychopath. The elements of that psychopathology vary in different individuals, but include the total or relative absence of empathy and compassion (see the destruction of Iraq, Libya and Syria, and the total indifference to the hundreds drowning while fleeing the Western created chaos)utter unscrupulousness (examples legion)gargantuan, indeed insatiable greed, unbounded narcissistic egomania, paranoia etc. This type created an operating system, capitalism, that empowers them, and destroys all existence, natural resources, the biospheres that make the planet habitable for our species and humanity itself, in order to create and increase capital, a process without end. It is an exactly congruent process with neoplasia, and the ruling capitalists and their employees, the politicians and various apparatchiki, are metastases. The host, the living planet, and humanity, for this process, is already cachectic, and the end stage looms near. We disappear, soon, unless we excise this cancerous process from humanity and the planet.

  8. Thanks, this is very interesting, i always wondered about that...
    Would you also know by any chance, just to compare, how many tons of CO2 we would emit under RCP 2.6/4.5/6/8.5 for the same timeframe as in the Jean Laherrere's graph (1850-2200)?

  9. Yes it could save us from burning fossil fuels however on the other hand it may switch to burn biomass in much bigger quantities!

  10. Great article thanks for sharing!



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)